The Active Female: Health Issues Throughout the Lifespan 2008th Edition

30. Ergogenic Aids and the Female Athlete

Shannon L. Jordan  and Fernando Naclerio 

(1)

Department of Kinesiology, Texas Wesleyan University, Ft. Worth, TX, USA

(2)

Centre of Sport Science and Human Performance, University of Greenwich, School of Science, Kent, UK

Shannon L. Jordan (Corresponding author)

Email: sljordan@txwes.edu

Fernando Naclerio

Email: f.j.naclerio@gre.ac.uk

Abstract

Female athletes tend to choose their supplements for different reasons than their male counterparts. Collegiate female athletes report taking supplements “for their health,” to make up for an inadequate diet, or to have more energy. Multivitamins, herbal substances, protein supplements, amino acids, creatine, fat burners/weight-loss products, caffeine, iron, and calcium are the most frequently used products reported by female athletes. Many female athletes are unclear on when to use a protein supplement, how to use it, and different sources of protein (whey, casein, and soy). This chapter addresses essential amino acid and branched chain amino acid supplementation. Along with recommendations for protein supplementation, creatine supplementation is discussed. Not all female athletes are concerned with building muscle. Burning fat is also a major concern for the female athlete. This may result in the athlete turning to products marketed for weight control (i.e., ginseng or ephedra). A product legal for over-the-counter (OTC) sales, however, can be illegal for athletic competition (i.e., ephedra). Competitive athletes should be aware of the banned substance list for their governing body and that OTC products are not currently regulated by the FDA. This lack of regulation can lead to OTC products that are contaminated with banned substances.

Keywords

Anabolic steroidsBCAACreatineEchinaceaEphedraGinsengProteinSupplement

30.1 Learning Objectives

After completing this chapter, you should have an understanding of:

·               Reasons why female athletes take supplements

·               Various supplements female athletes are likely to take

·               Ergogenic and ergolytic effects of these supplements

·               Variations within certain supplements and standard dosages

·               That many nutritional supplements are contaminated with banned substances

30.2 Introduction

Many things ingested by women can be considered ergogenic. Ergogenic aids, by definition, are items or substances which enhance performance. Female athletes tend to choose their supplements for different reasons than their male counterparts. Collegiate female athletes report taking supplements “for their health,” to make up for an inadequate diet, or to have more energy [12]. Interestingly, while many athletes report using energy drinks and calorie replacement bars or drinks, most of them did not consider these products to be supplements [2]. The subsequent sections will provide insight into the mechanisms and possible benefits (or lack thereof) for ergogenic aids that female athletes commonly cite ingesting.

30.3 Research Findings

30.3.1 What Are Female Athletes Taking?

Multivitamins, herbal substances, protein supplements, amino acids, creatine, fat burners/weight-loss products, caffeine, iron, and calcium are the most frequently used products reported by female athletes [13].

When compared to female nonathletes, female athletes consume similar amounts of performance-enhancing drugs (25.2–29.8 %, respectively) [4]. Performance-enhancing drugs included methamphetamines, ephedrine, university-banned substances, and weight-loss and nutritional supplements [4]. Female athletes reported using performance-enhancing drugs 21.5 % of the time during a competitive season and 25.9 % in the off season [4]. Many female athletes list taking Echinacea and cite “boosting the immune system” as the reason for taking it [135]. However, there are recent reports that Echinacea may also be performance enhancing as well [67].

While many studies do not report steroid use, Congeni and Miller found female adolescent steroid usage to be up to 2.5 % [8]. Other researchers have found that 5.1 % of middle school female students have already reported steroid use by the age of 12 [9]. In a 2009 report from the National Collegiate Athletic Association (NCAA), the use of anabolic steroids increased from 2005 to 2009 in the following women’s sports: lacrosse (0–0.2 %), swimming (0.3–0.4 %), and track (0.1–0.2 %) [10]. Frequency of use in other women’s sports such as basketball, field hockey, golf, soccer, and volleyball either remained the same or the prevalence of steroid usage actually decreased [10]. Female athletes may also take “fat-burning” supplements in order to maintain or improve body composition [4]. Female athletes reported a 5.1 % increase in usage of weight-loss products in the off season [11].

30.3.2 Protein and Amino Acids

Female athletes tend to take their protein supplements in the form of powders, bars, or as meal replacements [12]. Some female athletes also use amino acid supplements [2]. When classified by type of sport, athletes (men and women) who play a sport involving a mixture of aerobic and anaerobic energy systems consume the most protein supplements [2]. Aside from listing protein powders, protein bars, and amino acids, the most prevalent protein supplement reported by females were meal replacement drinks. When asked why they take protein supplements, females responded: “for enhanced recovery, just like the taste, provide more energy, to meet nutritional needs, enhanced performance, greater muscle strength, and don’t know” [1]. When these same athletes were asked if they had questions about protein supplement usage, there were several questions or concerns: increasing lean body mass and losing body weight, adverse effects on the kidneys, positive vs. negative effects, how much to consume, and whey vs. soy protein.

There is insufficient data to support a determination of whether differences in the quantitative requirements for protein or any individual indispensable amino acids exist between adult, men, and women. With the exception of some specific scientific findings, no reference to gender will be emphasized. However, in order to highlight the special need for females, some particular recommendations related to women will be given.

The protein requirements for certain athletic populations have been the subject of much scientific debate. During the last decade, the notion that both strength/power and endurance athletes, as well the general active population (including men and women), require greater protein consumption than the current RDA recommendation of 0.8 g/kg of body weight per day in healthy adults is becoming generally accepted [1213]. In addition, high-protein diets have also become quite popular in the general population as part of many weight reduction programs [1415]. In fact, in addition to the positive effects for optimizing protein synthesis and improving the recovery after training, a particular emphasis has been placed on the role of protein for weight management [1617].

Differences in protein requirements for athletes and nonathletes and different types of athletes (i.e., endurance, strength/power) are well documented [1821]. During the last 20 years, studies have investigated the effects of protein obtained from different sources such as milk or soy, as well as the technique used to manufacture the protein extract or the methodology recommended for their ingestion. Specifically, these factors can be of great importance when the protein is ingested in regard to augmenting the acute physiological response to a training session or in enhancing recovery from exercise in general [22].

Regarding women, it has been observed that female athletes tend to take in their protein supplements as powders, bars, or in meal replacement products [2]. In addition to protein, some female athletes also ingest amino acid supplements [223]. A considerable number of regular strength training adepts (including men and women) consume protein supplements mixed with other products (mainly creatine and amino acids). However a limited number of individuals consult “dietary specialists” and rely mainly on their instructors [23]. For males and females, the most common reason given for protein or amino acid consumptions is to increase strength or train longer [24].

For pregnant and lactating women, the amino acid requirement is taken to supplement the extra dietary need associated with the deposition of protein in tissues or secretion of milk at rates consistent with good perinatal health. Researchers have shown that a balanced protein energy diet in expectant females leads to reduction in the risk of small for gestational age infants, especially among undernourished pregnant women [25].

30.3.2.1 Protein Powders

Most of protein extracts are obtained from milk, eggs, bovine colostrums, soy, and, to a lesser extent, bean, wheat, or rice. The quality of the extract may vary depending on the type and quality of the manufacturing process [2627]. In this section we will analyze the three principal forms in which most protein supplements are currently found in the market: whey, casein, and soy.

Whey

Whole milk is composed of approximately 87 % water, with the remaining 13 % being solids. The solid proportion is composed of 30 % fat, 37 % lactose, 27 % protein, and 6 % minerals. Of the 27 % of milk which is protein, 20 % is whey and 80 % casein protein [28]. During the process of making cheese, whey protein is separated out into a transparent liquid fraction which has shown to be a good source of high-quality protein currently used to make protein powders and many other products. Whey protein is particularly rich in essential amino acids (EAA), vitamins, and minerals [26].

The whey protein fraction is composed of numerous individual proteins, including β-lactoglobulin (50–55 %), α-lactalbumin (20–25 %), bovine serum albumin (5–7 %), lactoferrin (1–2 %), immunoglobulins (10–15 %), lactoperoxidase enzymes, and glycomacropeptides (~0.5 %) [26]. These proteins are involved in several health and immune system functions [29]. The amount of these native proteins remaining intact in the final whey product depends on the processes used to separate out the fat and lactose while the proteins are being purified. Selective elution, also known as ion exchange chromatography, is the process most often used to make whey protein isolates. With the high-quality of manufacturing, the native protein structures can be retained. However, some of the smaller peptides such as lactoferrin may have a decreased concentration, while the β-lactoglobulin protein fraction tends to increase in whey protein isolates [28].

Collectively, whey proteins contain all the EAAs. Relative to other protein sources, whey has a high concentration of cysteine and the branched chain amino acids (BCAA)—leucine, isoleucine, and valine. However, whey protein contains lower quantities of glutamine, arginine, and taurine. Since these amino acids have important neuronal and metabolic functions, it is advisable to fortify whey protein extract by adding peptides of L-glutamine, L-arginine, and taurine [2627]. For instance, glutamine is the most abundant amino acid in the blood, accounting for 30–35 % of amino acid nitrogen in the plasma. L-glutamine fulfils a number of biochemical needs. It operates as a nitrogen shuttle, taking up excess ammonia and forming urea. It can act as a powerful anticatabolic agent contributing to the production of other amino acids, glucose, nucleotides, protein, and glutathione [30]. Arginine is a semi-essential amino acid, involved in numerous areas of human biochemistry, including ammonia detoxification, hormone secretion, and immune modulation. L-arginine is the main physiological precursor of nitric oxide (NO), which plays an important regulatory role by increasing blood flow to the muscles and modulating muscle contraction, along with glucose and amino acid uptake by the muscle [31]. Taurine is a conditional EAA involved in a number of physiological processes including cell membrane stabilization, neural excitability or sensibility, and nutrient intake into the cell. Even when taurine is the most abundant free amino acid in excitable tissue such as muscle heart and brain, it is not used to build protein but has other important functions as insulin mimetic, cellular hydration, and protein synthesis stimulation [32].

In addition to the positive effects observed in athletes, in sedentary or slightly active individuals, 50 g/d of whey protein supplement added to a hypocaloric weight-loss diet has shown positive effects to maintain lean tissue relative to a change in adiposity. This results in greater weight gain of relative muscle mass compared to the dietary addition of a similar amount of carbohydrate in older postmenopausal, overweight, or obese women [33]. It seems that the addition of whey protein supplements during weight-loss plans in women could be a good strategy to offset the deleterious effects of both sedentary and aging on muscle mass and bone loss. Additionally, when a high-quality protein supplementation is appropriately combined with a well-designed long-term resistance training program, significant positive effects on physical performance, maintenance or gaining of muscle mass, and improved bone density have been reported [3335].

Casein

Casein accounts for approximately 75–80 % of total milk protein and is responsible for the white color of milk [27]. Casein consists of three different protein fractions: α-casein, β-casein, and κ-casein. It is the protein source of cheese and forms curds during processing because it exists as a micelle in milk [28]. Because native casein has low solubility and forms clumps or curds, casein used in nutritional supplements is made into rennet casein or caseinates, an acid form that is usually combined with sodium, calcium, or potassium.

Compared to the whey protein form that remains soluble in the stomach and thus is emptied rapidly, casein is converted into a solid clot, thus emptied more slowly from the stomach [36]. These differences in digestive properties likely contribute to the variation in the pattern of amino acid concentrations that have been observed after ingestion of whey, soy, or casein protein. Casein has been termed a “slow” protein, and whey protein has been named a “fast” protein [3637]. The slowly absorbed casein protein would promote a more sustained and prolonged postprandial protein deposition via inhibition of protein breakdown without an excessive increase in amino acid concentration. By contrast, a fast whey protein stimulates protein synthesis but also oxidation. The impact of amino acid absorption speed on protein metabolism is true when proteins are given alone; however, this effect might be blunted in more complex meals that could affect gastric emptying (lipids) and or insulin response (carbohydrates) [38]. Additionally, the more prolonged anabolic effects of casein seem to be most effective when consumed in the rested condition [18]. In contrast, ingestion of a single dose of whey protein stimulates an anabolic response when consumed postexercise [39].

Soy

Soy is the most widely used vegetable protein source and it is reported to have equivalent quality to egg or milk protein [40]. Soy’s quality makes it a very attractive alternative for those who are lactose intolerant. Soy is a complete protein with a high concentration of BCAA’s, plus arginine, moderate amounts of glutamine, and low amounts of methionine [37]. There have been many reported benefits related to soy proteins affecting health and performance (including reducing plasma lipid profiles, increasing LDL-cholesterol oxidation, and decreasing blood pressure) [41]. These health-related benefits have been attributed to the amount of isoflavones which are naturally active nutrients contained in soy protein. Isoflavones’ molecular structure is similar to natural body estrogens (phytoestrogen). The following foods contain anywhere from 1 to more than 5 mg/g of isoflavones: tofu, green soybeans, mature or roasted soybeans, and soy flour [41]. Another product made from soybeans is textured soy protein. This product is the typical protein source in imitation chicken, pork, or other meat products. Textured soy protein is also used in numerous other soy protein products which tend to retain the original isoflavone content [28].

Soy products of up to 60 g/d have been safely used in studies lasting up to 2 months [42]. During pregnancy, ingestion of soy protein has been reported as safe when consumed orally in amounts naturally found in foods. However, soy could be unsafe when used orally in medicinal amounts due to its estrogenic constituents. Theoretically, therapeutic use of soy might adversely affect fetal development (i.e., feminization of the male fetus) [4243].

30.3.2.2 Whey, Casein, and Soy Protein Comparison

Many studies have examined the physiological effects of whey, casein, and soy protein supplements in isolation or combined with carbohydrate and other nutrients such as creatine, amino acids, or lipid-like compounds [4445]. However, until now there is no convincing evidence to support the notion that whey, casein, or soy could be a superior protein source for athletes and other active individuals including women. Indeed, each protein source has unique attributes that may convey specific nutritional advantages when compared to the others. These benefits include boosting general health, body weight management, increased lean body mass, enhanced muscle recovery after exercise, and an ability to stimulate skeletal muscle protein synthesis. The differences in the degree by which each source of protein can stimulate the aforementioned processes are related to differences in digestion rates, divergent amino acid profiles, and the presence of naturally occurring antioxidants [37].

30.3.2.3 Responses to Ingestion of Different Protein Sources at Rest

The speed of amino acid absorption has a major impact on postprandial protein synthesis and breakdown responses after a meal. Since whey protein is absorbed faster than casein and soy, the appearance of circulating amino acids is more rapid and levels tend to be higher. This rapid increase is transient and, therefore, whey produces a fast but temporary increase of both whole-body protein synthesis and amino acid oxidation [46].

Casein tends to inhibit protein catabolism when consumed at rest and has a slight but relatively long effect of increase in protein synthesis. The pattern of amino acid delivery with casein ingestion at rest appears to lead to better leucine balance (net protein state) than whey consumption at rest. It is interesting to note that a single dose of casein ingestion does not lead to large increases in circulating levels of amino acids as was observed with the equivalent single dose of whey protein [18]. However, when the same amount of protein is ingested in smaller, more frequent feeding, whey seems to work more effectively to stimulate muscle protein synthesis and reduce amino acid oxidation as compared to casein [18].

Overall, it would appear that casein protein with its slow absorption rate leads to a greater positive net whole-body protein state than single feedings of whey protein or amino acids at rest. Additionally, frequent small feedings of whey protein may lead to the greatest net protein balance and potential gain in muscle mass [184647].

Isolate soy protein (ISP) has been shown to have faster absorption rates than casein but slower than whey. After ingesting a standardized dose of ISP, plasma amino acid levels peak at 150 min, as opposed to 75 min if a comparable dose of whey is consumed. Thus, it seems that soy isolate is more of an “intermediate” protein in terms of digestion rate based on plasma peak amino acid concentrations [37].

30.3.2.4 Responses to Ingestion of Different Protein Sources with Exercise

Both soy and whey protein similarly increase muscle protein synthesis rates when fed immediately after exercise [37]; meanwhile casein ingestion does not increase protein synthesis but ameliorates protein breakdown [38].

In both young and older individuals after a typical resistance training workout, whey protein has been shown to stimulate a greater acute (0–3 h postexercise) rise in muscle protein synthesis compared with dose-matched casein and soy proteins [4849], and it is still highly effective for stimulating muscle protein synthesis after 3–5 h postexercise [50]. As stated above, the mechanism underlying the robust anabolic properties of whey protein relative to casein is likely related to the more rapid digestion kinetics and greater appearance of circulating amino acids (specifically the BCAA leucine), which may be particularly important as a key metabolic regulator of muscle protein synthesis through activation of the mTOR pathway [4850]. The superior capacity of whey to stimulate protein synthesis after training compared to soy protein is not due to differing absorption kinetics but probably due to the lower leucine content of soy versus whey protein [37].

Regarding women, with a few exceptions related to BCAA effects, there is no comparative research aimed to determine different responses to protein or amino acid ingestion compared to men (51). However, sex has been shown to significantly influence metabolic fuel selection during endurance activity. Women appear to oxidize proportionately more lipid and less carbohydrate or amino acid compared to men [5253]. From a nutritional point of view, there is no reason to think that women will respond differently from men when being fed with the same relative amount of protein or the majority of amino acid adjusted per kg of body weight or lean body mass [54].

Table 30.1 summarizes the principal characteristics of whey, casein, and soy and shows how the combination of these three protein sources in a blended mixture can be useful to potentiate adaptation to exercises and obtain health benefits.

Table 30.1

Prospective benefits derived from blending whey, casein, and soy protein based on their unique attributes

Characteristic

Whey (W)

Casein (C)

Soy (S)

W + C + S

High quality

Yes

Yes

Yes

Yes

Absorption rate

Fast

Slow

Medium

Longest

Leucine

Yes

Yes

Glutamine

Yes

Medium

Yes

Arginine

Medium

High

Yes

Antioxidant

Yes

Yes

Hyperaminoacidemia

Short

Long

Short

Longest

Muscle protein synthesis stimulation

High

Low

Medium

Highest

Adapted from Paul, G. L. 2009. The rationale for consuming protein blends in sports nutrition. J Am Coll Nutr 28 Suppl: 464S-472S

Even though rapidly digested proteins may stimulate muscle protein synthesis, the associated high amino acid oxidation rates that could be produced after a large single dose can negatively affect protein retention over time [18]. This finding together with the difficulty in ingesting several frequent smaller portions of whey protein has led sports nutrition manufacturers to design blends of proteins involving different sources as the best strategy to obtain a timed release of amino acids into circulation. This feeding pattern has been associated with greater muscle protein synthesis rates and lean body mass gains [37]. The difference in digestion rates provided by the combination of whey, soy, and casein will effect the prolonged and increased levels of plasma amino acids resulting in greater muscle amino acid uptake [55]. Blending whey, casein, and soy protein stimulates a more balanced amino acid profile, specifically BCAAs, glutamine, and arginine. This may confer an advantage by providing a wider range of benefits for exercise adaptation and health-related effect compared to a single protein source rich in only 1 or 2 of these key amino acids. However, the exact ratio of protein sources to accomplish this task has not been reported. Moreover, the possibility exists that endurance athletes, because of their specific needs, would benefit from a different protein blend than the mixture used by strength/power athletes. Additionally, no specific recommendations have been made for active women or female athletes.

Collectively, the above analysis indicates that for most athletes and active individuals, achieving competitive advantages plus optimizing recovery and gains are the most important variables. Considering the intake of only one type of protein source (whey, casein, or soy), it would appear that casein leads to the optimal total body protein state at rest. However, following exercise, it would appear that ingestion of a whey source or a combination of whey, casein, or soy proteins would be the best options.

30.3.2.5 Essential Amino Acids

Nutritional intervention leading to an acute increase in muscle amino acid availability at rest or early after resistance exercise is a vital stimulus for promoting muscle protein synthesis [2036]. Regardless of sex when resistance exercise is followed by an increase in amino acid’s availability, the rate of muscle protein synthesis is increased more so than that observed with either exercise or amino acids alone [3656]. Table 30.2 lists the EAAs.

Table 30.2

Essential and nonessential amino acids

Essential

Nonessential

Isoleucinea

Alanine

Leucinea

Arginineb

Valinea

Asparagine

Lysine

Aspartic acid

Methionine

Cysteine

Phenylalanine

Glutamic acid

Threonine

Glutamine

Tryptophan

Glycine

Histidine

Proline

Serine

Tyrosine

Source: Reeds, PJ. Dispensable and indispensable amino acids for humans. J. Nutr. 2000:130:1835S–1840S

aBranched chain amino acids

bNot considered essential as most humans synthesize arginine

Research indicates that ingesting 3–6 g (>45 mg to 86–95 mg/kg body weight) prior to and/or following exercise can significantly stimulate protein synthesis [192257]. Although more data is needed, there appears to be strong theoretical rationale and some supportive evidence that EAA supplementation may enhance protein synthesis and training adaptations [22].

Hence, an “anabolic window” appears to exist from immediately to a few (1 to 2–3) h after a workout. This helps to explain why weight training combined with feeding protein during the early hours after exercise leads to significant increases in lean body mass compared to delaying the same feeding [5859] and why the failure to increase glucose and amino acid availability during recovery could significantly delay or even hinder the recovery process resulting from reduced muscle protein synthesis and glycogen restoration [60].

In sedentary or slightly active healthy older women, twice-daily between-meal ingestion of 7.5 g/d of EAA (15 g total) for 3 months has been shown to effectively retard the loss of muscle mass associated with aging. This regimen may stimulate muscle synthesis in the period between meals when blood amino acid concentration tends to decline [56]. However, it seems that elderly men and women could show a blunted muscle protein synthesis response when given the minimal effective 3 g (45 mg/kg body weight) dose of EAA proven to increase synthesis in younger counterparts [61]. The mechanism facilitating the impaired dose response in muscle protein synthesis in the elderly compared with the young is still elusive.

The possible existence of a leucine “threshold” that must be surpassed after protein or EAA ingestion in order to stimulate muscle protein synthesis above rest would explain not only the minimal effective dose for improving exercise benefits but also the observed varied responses between young and older men/women. This leucine threshold seems to be lower in younger rather than older populations. This could be one of the explanations as to why younger muscles are highly sensitive to the anabolic actions of leucine, as ~1 g of orally ingested leucine would be sufficient to elicit significant gain in muscle protein synthesis above the resting state [50]. Meanwhile, 2 g of leucine have been needed to produce a comparative response in the elderly [62]. Thus, when considering protein feeding strategies to stimulate muscle hypertrophy, a protein source with high leucine content and rapid digestion kinetics or an EAA dose that includes 2 g of leucine should be considered in order to promote a transient leucinemia “spike” for an effective option [61].

This recommendation is in line with recent recommendations from the International Society of Sports Nutrition [59]. In order to elevate muscle protein synthesis and favor a positive muscle protein balance, it is advisable to distribute the daily protein ingestion equally across four to five meals. For example, in addition to the protein included in typical food (milk, meat, etc.), the consumption of 15–30 g (~300 mg/kg body weight) of high-quality protein containing 4–8 up to 15 g (>50 to ~150 mg/kg body weight) of EAA in the form of powder or protein bar supplements could be adequate for making shakes [466364]. The typical American or some European diets distribute protein intake unequally in such a manner that lower amounts of protein are consumed with breakfast (>10–14 g of protein) when compared to dinner (>15 g). The use of protein powder or bar supplements can help to maintain an equal distribution of protein ingestion through the day. This strategy has been shown to be more effective for maintaining muscle mass when compared to an unequal distribution of protein contained within the daily meals.

30.3.2.6 How to Use Protein and Amino Acid Supplementation

As stated above, there is no special recommendation for female or male athletes. In general, to optimize the positive outcomes elicited by any exercise program, the ingestion of food containing a 50 mg/kg of EAA seems to be the minimum amount or threshold to trigger a significant increase in muscular protein synthesis [64]. However, research has shown that ingesting a combination of EAA or protein including 1–2 g of leucine with carbohydrates and other natural compounds such a creatine immediately prior to the workout may stimulate the most profound changes [456566]. Ingestion of carbohydrate alone after exercise causes marginal improvements in overall protein synthesis while maintaining a negative net protein balance. When combined with protein or EAA, carbohydrates stimulate a more powerful insulin secretion that enhances cellular hydration and nutrient intake, favoring a more positive environment to attenuate catabolism and stimulate a greater anabolic response [60].

Unfortunately, there is no conclusive evidence regarding what time frame is the most optimal period to ingest a protein or amino acid-carbohydrate supplement in order to optimize muscular adaptation to exercise. Many studies have provided support for ingestion of different nutrients before, during, or immediately after to several hours (1–3 h) postexercise in order to promote increases in protein synthesis [21586668]. Similar changes have been found in studies that have administered amino acids alone or with carbohydrate during and immediately upon completion of an acute exercise bout, 1, 2, and 3 h after completion. However, ingesting nutrients before an exercise bout may have the most benefit of all the time points observed [66].

From the currently published research, the optimal dose of a multinutrient supplement containing high-quality protein or EAA with carbohydrates is difficult to determine. However, in order to stimulate a more powerful anabolic response, just prior or during an intermittent high-intensity or resistance training workout, it would be advisable to ingest a beverage containing 0.4 g/kg of carbohydrates mixed with 50 mg/kg of EAA or approximately 100 mg of a high-quality whey protein dissolved in 0.750–1 l of water. This beverage will provide a nutrient concentration of around 8 % in order to be adequately assimilated throughout the digestive tract [64]. An optimal post-workout meal aimed to potentiate exercise benefits could include 1.2–1.5 g/kg of high-glycemic load carbohydrates with 50–150 mg/kg of EAA or 115–300 mg/kg high-quality whey protein [64].

30.3.2.7 Branched Chain Amino Acids

The EAAs leucine, isoleucine, and valine form what is referred to as BCAAs. BCAAs comprise about 1/3 of the total muscle protein pool [69] and act as a primary nitrogen source for glutamine and alanine synthesis in muscle [70]. Unlike most free form AAs, BCAAs are not degraded in the liver. Twenty to thirty percent of ingested BCAAs from food or supplements are metabolized by the intestine; the rest are rapidly absorbed in plasma. Muscle tissue BCAA uptake primarily occurs from plasma BCAAs [71].

Supplementation with BCAAs has been shown to acutely stimulate protein synthesis, aid in glycogen resynthesis, delay the onset of fatigue, and help maintain mental function with aerobic-based exercise. Researchers have concluded that consuming BCAAs (in addition to carbohydrates) before, during, and following an exercise bout could be recommended safe and effective [22].

One of the proposal effects of BCAA supplementation relates to a phenomenon known as central fatigue, which signifies that mental fatigue in the brain can adversely affect physical performance in endurance events. The central fatigue hypothesis suggests that low blood levels of BCAAs may accelerate the production of the brain neurotransmitter serotonin, or 5-hydroxytryptamine (5-HTP), and prematurely lead to fatigue [72]. Tryptophan, an EAA, is a precursor of serotonin which can be more easily transported into the brain (to increase serotonin levels) when BCAA plasma concentrations decrease [72]. This occurs during prolonged exercise due to an increased BCAA intake by the active muscle [72]. In addition, the increased release of fatty acids into the blood during endurance exercise displaces tryptophan from its place on albumin and facilitates the transport of tryptophan into the brain for conversion to serotonin. Thus, the combination of reduced BCAAs and elevated fatty acids in the blood causes more tryptophan to enter the brain and more serotonin to be produced, leading to central fatigue [7273]. Due to these metabolic processes, it has been hypothesized that BCAA supplementation can help delay central fatigue and maintain mental performance in endurance or extremely long-lasting physical activities [67].

The positive effect of administration of BCAAs in reducing fatigue in exercise may also be due to its possible influence on other biochemical events in the brain. BCAAs may be involved as precursors for the synthesis of several neurotransmitters. In this model, leucine would act as a neurotransmitter per se, being that one of its role is to counteract fatigue. Alternatively, a BCAA (e.g., leucine) may be converted into a metabolite, which is a novel neurotransmitter that also could reduce fatigue [74].

Other documented effects of BCAA supplementation are the ability to attenuate delayed-onset muscle soreness (DOMS) and suppress the decrease of muscle strength after an unaccustomed high-volume resistance training workout in untrained women [75]. These effects have been shown to be more pronounced in women as compared to men when BCAAs were ingested at 77 mg/kg body weight (males) or 92–100 mg/kg (women) before exercising [76].

30.3.2.8 How to Use Branched Chain Amino Acids as a Supplement

Due to the possible benefits to the recovery process, stimulating protein synthesis, aiding in glycogen resynthesis, delaying the onset of fatigue, and helping to maintain mental function, it is advisable to ingest BCAAs with carbohydrates before, during, and following an exercise bout. Before and during exercise, BCAAs could be added to a sports drink with 6–8 % of carbohydrate concentration [64]. In order to improve glycogen recovery and stimulate protein synthesis after exercise, the addition of BCAAs to a carbohydrate-rich beverage with a BCAAs/CHO ratio of 1:4 (67)–1:7 (64) has been recommended.

30.3.2.9 L-Glutamine

While amino acid usage tends to be more prevalent in male athletes, female athletes are also consuming amino acid supplements [2]. Aside from amino-stacked supplements, female athletes also admitted to have listed taking glutamine individually. Glutamine is a common component of weight-gain products. A small percentage of female athletes report taking weight gainers as well [2].

As stated before, glutamine is the most abundant amino acid in plasma and skeletal muscle representing more than 60 % to total free plasma amino acid [77]. Glutamine plays a number of important physiological roles by acting as an antioxidant, immuno-suppressor, and anticatabolic agent [78]. Amino acids along with alanine, glutamine acts as nontoxic nitrogen carrier which makes these important carbon donors for glycogen synthesis in the liver [79]. Despite its important physiological roles, there is no compelling evidence to support glutamine supplementation in terms of increasing lean body mass or muscular performance in male or female athletes [22]. In addition, previous reports have not indicated any evidence about the protective effects of glutamine supplementation against immuno-depression caused by high-intensity and prolonged endurance exercise sessions [80]. However, in some high-intensity endurance exercise conditions where plasma glutamine concentration could fall to 20–25 %, ingestion of an amino acid and in particular L-glutamine could be advantageous for cells of the immune system, including neutrophils [81]. In addition, supplementation with L-glutamine seems to protect mitochondrial integrity and thereby potentially reduce exercise-induced apoptosis [82].

In conclusion, in spite of the lack of convincing evidence regarding the effects of glutamine to maintain or gain muscle mass and increase physical performance, animal experiments suggest that the usefulness of glutamine supplementation is more related to its capacity as an immunoprotector. As an immunoprotector, glutamine could regulate neutrophil activity and counteract the negative effects of exercise on specific neutrophil functions such as apoptosis and nitric oxide (NO) production [82].

How to Use Glutamine as a Supplement

In athletes (both males and females), a dose of glutamine 40–50 mg/kg body weight ingested before and within 2 h after a workout has been proposed to improve anabolic cellular environments or attenuate immuno-depression after prolonged high-intensity endurance exercise [64].

30.3.2.10 L-Arginine

Arginine is, conditionally, an EAA synthesized from ornithine and citrulline. Arginine is a precursor amino acid for several important components such as creatine, phosphate, polyamines, and NO. Supplementation with L-arginine is claimed to promote vasodilatation by increasing NO production in the active muscle during exercise, improving muscular strength, power, and recovery through increased substrate utilization and metabolite removal, such as lactate and ammonia [83]. In males, supplementation with L-arginine has shown to be effective for improving endurance exercise performance and possibly improve maximal muscle strength and power [83]. Regarding females, only few studies have analyzed the effects of L-arginine supplementation. Fricke et al. observed no significant difference in maximal isometric grip force (N) and jump performance variables after 6 months of L-arginine supplementation (18 g) in postmenopausal women (23, 84).

Even though current research in men is promising regarding the positive effects of L-arginine supplementation, more research is needed in order to give conclusive recommendation about L-arginine use in female athletes or active women.

How to Use Arginine as a Supplement

L-arginine supplementation appears to be safe and well tolerated when used between 3 and 15 g orally in healthy subjects. No further dosages have been used in similar groups with the purpose of improving performance. As stated above, further studies (particularly in active females) are required to determine its potential ergogenic aid as well as associated side effects. In general, it has been proposed for athletes to ingest 3–5 g/d before training or competition as a possible effective strategy to improve performance [64].

30.3.2.11 Carnitine

Carnitine is synthesized from lysine and methionine, which are the amino acids that soy protein is lacking. Mammals synthesize carnitine and most healthy humans can synthesize it even with a diet lacking in animal protein. In times of low dietary consumption, daily losses through excretion are lowered to compensate for this reduction [85].

When marketed as L-carnitine, an isomer of carnitine, it has been touted as a fat burner. As such, athletes have taken it for weight loss, increased muscle mass, and enhanced β-oxidation. While L-carnitine is involved in transportation of fatty acid chains across the membrane, studies have generally shown it to be an effective weight-loss agent for obese subjects and inconclusive for healthy non-obese subjects [85].

Athletes may also take L-carnitine to enhance recovery high-intensity exercise. Research findings include decreased creatine kinase, production of purine, reduced free radical formation, and less reported muscle soreness [85].

L-carnitine is available as a supplement and also as a prescription. Recommendations for daily supplementation are 2–3.5 g/d. Amounts in excess of 4 g/d may cause gastrointestinal distress. A lethal dose (LD) of 630 g/d in humans has been extrapolated from studies using rats [85].

30.3.2.12 Creatine

Creatine is traditionally taken by men more than women [12]. However, a large enough percentage of women are taking it to make creatine worthy of discussion.

Creatine is composed of two non-EAAs (arginine and glycine) and one EAA (methionine) [86]. The average daily requirement is 2 g/d [886]. The body makes 1–2 g/d via the liver, kidneys, and pancreas. Meat and fish also contain creatine. Vegetarian athletes have lower muscle creatine than omnivores [87].

Creatine is an important part of the adenosine triphosphate phosphocreatine (ATP-PC) energy system. Phosphocreatine (PC) is used to phosphorylate adenosine diphosphate (ADP) to ATP during high-intensity maximal muscle contractions, resulting in ATP and free creatine. Creatine is rephosphorylated during periods of rest via aerobic pathways (mitochondrial creatine kinase). Generally speaking, an average person has enough phosphocreatine stores to supply ATP for anaerobic activities up to 10–15 s [886]. Since the ATP-PC system is short-lived, glycolysis becomes the dominant energy system as PC stores are depleted and ADP builds up. Rest periods required to regenerate PC are typically >3 min [8].

Creatine supplementation increases muscle creatine stores in subjects who do not already have maximal stores. Some athletes who consume high quantities of meat or fish are thought to have maximal or near-maximal stores already [86]. Increased muscle creatine stores may lead to more PC to regenerate ATP, a faster recovery time to rephosphorylate free creatine and in some cases buffer lactic acid [88688]. However, some researchers have reported no ergogenic effect on anaerobic exercise [41718]. Furthermore, aerobic endurance-type activities and submaximal efforts will not show any improvement with creatine supplementation [8].

Creatine is usually taken in the form of creatine monohydrate with a loading phase (5 g/d, 4 Xs/d) up to 7 days. A maintenance phase of 2 g/d is recommended for 3 months. This protocol has shown increases of muscle creatine 10–25 % [8689]. Consumption of creatine with a carbohydrate enhances absorption while caffeine will inhibit absorption [86].

Consumption of creatine above the recommended dosages may result in excretion. Since creatine consumption has been linked to dehydration cases, it is best to advise the athlete to consume plenty of water while taking creatine, especially when exercising in the heat [86].

Benefits and Side Effects of Creatine Using the Recommended Loading-Maintenance Creatine Protocol

There are reports of increased ability to perform more reps at a given percent of 1 repetition maximum (RM), enhanced power output in cyclists, improved track sprint times by 1–2 %, increased muscle mass, and lower percent body fat with creatine supplementation [886878990]. Other studies have not demonstrated any improvement of these same variables [8868890]. Creatine supplementation was ineffective in subjects 60 years and older or in people with high creatine levels before supplementation. These subjects are referred to as nonresponders [8688]. Although tennis has various components (i.e., serve or sprint to the net) that would utilize the ATP-PC system, no benefits of creatine supplementation have been reported with the stroke or sprint performance [8]. Some ergogenic findings in exercise lab environments may not translate into actual competition.

Side effects of creatine include weight gain from water retention, gastrointestinal discomfort, and muscle cramps [88688]. Increased weight gain may hinder performance in mass-dependent sports. Additionally, it has been speculated that long-term use may downregulate the creatine transporter protein and render creatine supplementation less effective [88].

30.3.3 Fat Burners and Energy Supplements

30.3.3.1 Ginseng

Ginseng is a widely used herbal supplement in many fat burners and energy drinks. It is reported to improve mood, performance, and alertness and increase fat utilization. There are two prevalent types of ginseng used: Chinese ginseng (Panax ginseng) or Siberian ginseng (Eleutherococcus ginseng). Other less commonly used ginseng plants include Japanese ginseng (P. japonica), Tienchi ginseng (P. notoginseng or P. pseudoginseng), Dong Quai (Angelica sinensis), or American ginseng (P. quinquefolius) [91].

Chinese ginseng is an herbal supplement that has been evaluated in human performance studies and was reported to exhibit promising effects to improve strength and aerobic capacity [9192]. However, other studies have shown no improvements in maximal oxygen consumption (VO2max), strength performance, or postexercise recovery [9193]. This could be due to varying populations, different dosages, types of ginseng, or various durations of the studies [9395]. The general dosage guidelines for Chinese ginseng are 1–2 g/d. This may vary based on type of preparation (powder vs. root extract). Chinese ginseng is usually supplemented for a certain duration in combination with athletic training [91]. The majority of research suggests that Chinese ginseng is not ergogenic.

Eight weeks of supplementation with Panax ginseng in 24 healthy active women did not result in improvements of supramaximal exercise testing or recovery values [96]. Participants consumed 400 mg of Panax ginseng for 8 weeks or consumed their normal diet. Prior to the treatment period and at the end of treatment, participants performed a Wingate cycle ergometer test. There were no significant differences for mean power output, peak power output, rate of fatigue, or recovery heart rate (HR) [96].

There have been some adverse effects reported with Chinese ginseng use. As ginseng is a stimulant, it may cause sleeplessness or nervousness. Since many supplements contain ginseng plus caffeine, this side effect may not be due entirely to ginseng. Hypertension, dermatological problems, morning diarrhea, and euphoria have also been reported with ginseng use [9192].

Siberian ginseng is in the same plant family as Chinese ginseng. However, the two herbs are distantly related. It does contain saponins, but they are different than the ones found in Chinese ginseng. Many of the early studies involving Siberian ginseng did not give experimental design details or data, nor were they peer reviewed. Subsequent studies have failed to show an ergogenic effect [8797]. Dowling et al. [97] examined the effects of Siberian ginseng on submaximal and maximal exercise tests in 20 trained distance runners. After 8 weeks of supplementations, no differences existed between placebo and treatment groups for VO2, ventilation (VE), respiratory exchange ratio (RER), HR, or rating of perceived exertion (RPE) in both the submaximal runs at 10 k race pace or maximal treadmill tests. There were also no differences in lactate and time to exhaustion during the maximal testing [97]. Without further research demonstrating an effect, it would be difficult to recommend supplements containing Siberian ginseng for athletic activity.

30.3.3.2 Echinacea

Multiple studies have reported that female athletes commonly use Echinacea in order to boost their immune system [135]. In fact, Echinacea supplementation is commonly listed in the top 5 supplements which female athletes consume. In fact, research suggests that supplementation with various Echinacea species or preparations does not prevent or shorten the duration of a cold [98100].

Turner [2899] treated 50 participants with 900 mg/d Echinacea and 42 participants with placebo and found no significant difference between rhinovirus infection (44 and 57 %, respectively) and clinical colds (50 and 59 %, respectively). The duration of the treatment period in this study was 2 weeks [99].

Turner also examined the dosage of 900 mg/d in three different preparations of Echinacea angustifolia on the varieties of Echinacea recommended to treat a cold [100]. Participants were assigned to receive the treatment either as a prevention of or treatment for a cold. After a week of supplementation, participants in the prevention group were given a nasal spray containing a rhinovirus. There was no positive treatment effect of Echinacea with regard to infection prevention. Treatment of infected participants did not result in any significant effects on alleviating rhinovirus symptoms [100].

In agreement with Turner and colleagues, Barett et al. [98] found that supplementation with an Echinacea supplement made of Echinacea purpurea (675 mg) and Echinacea angustifolia (600 mg) did not reduce the duration or ease symptoms of a cold. Participants in the treatment group consumed 2 tablets, 4 times/d the first day and 1 tablet/d for the next 4 days. Symptoms were tracked for 2 weeks. There were no significant differences in cold duration or relief of symptoms in any group studied [98].

Echinacea and Erythropoietin

Recently, a study has been published suggesting that Echinacea could be an ergogenic aid, not used to treat cold symptoms, but to increase Erythropoietin (EPO) and subsequently increase VO2max [6]. Whitehead et al. [6] administered 8,000 mg/d (most over-the-counter [OTC] Echinacea supplement doses are far less than this) Echinacea purpurea to 24 healthy male college students for 4 weeks. Blood samples were taken pre-study and then at 7 days, 14 days, 21 days, and 28 days. After day 7, EPO values were increased over baseline as compared to the placebo group. However, while at day 21 even though EPO values were still significantly elevated, they had started to decline. By day 28, EPO values were no longer significantly elevated over baseline or different from the placebo group. Red blood cell (RBC) count was not different between groups or within groups. Submaximal VO2 was ~1.5 % lower from pre-study values during the first 3 stages of the maximal exercise test in the Echinacea group. VO2max was ~1.5 % higher in the Echinacea group [6]. From the results of this study, it appears that high doses of Echinacea may increase VO2max while allowing an endurance athlete to perform the same amount of work at a lower submaximal VO2. It also appears that Echinacea may increase EPO up to 2 weeks and then wane. In this study, the maximal exercise test was given at 28 days. It would be interesting to know what VO2 values looked like at 2 weeks when EPO was at the highest levels. It is also worth noting that, in this study, Echinacea increased EPO without increasing RBC count [6]. Future research should be conducted before recommending Echinacea to increase VO2 . Increases in EPO typically increase RBC count and can result in serious side effects such as increased viscosity of the blood and increase the likelihood of a cardiac event. High levels of EPO may also cause an athlete to fail a drug test as well.

30.3.3.3 Ephedra

Ephedra contains ephedrine and other alkaloids which are sympathomimetic possessing α- and β-agonistic properties. It facilitates catecholamine release and stimulates the central nervous system (CNS) [8691101]. Ephedra is used as an energy booster, fat burner, and athletic performance enhancer. Ephedrine is also a component of cold remedies and some prescription drugs [91101]. Ephedra may also go by the name of Ma Huang.

Ephedra has been reported to aid in weight loss and was a popular ingredient before the 2004 ban by the Federal Drug Administration (FDA) [102]. The ban was overturned on an appeal and reinstated after a further appeal. This had led to consumer confusion regarding the legality of ephedra found in supplements. Currently, the FDA ephedra ban specifically lists “ephedrine alkaloids” as an adulterated substance that presents unreasonable risks [102]. Under the definition of the ban, ephedrine alkaloids are listed as raw botanical and botanical extracts from the following sources: species Ephedra sinica Stapf, Ephedra equisetina Bunge, Ephedra intermedia var. tibetica Stapf, Ephedra distachya L., Sida cordifolia L., and Pinellia ternata (Thunb). Some dietary supplement companies are manufacturing products using other ephedra varieties, most of which do not produce the same effects as the alkaloids from the variety banned by the FDA. Even though ephedra is not legal in supplements, the ban does not regulate the usage of synthetic ephedrine in cold, allergy, or asthma OTC medications.

Ephedra is often paired with caffeine in supplements to achieve an enhanced response [86101103]. Unfortunately, many of the studies involving ephedra and athletic performance also included caffeine. Shekelle et al. [103] found few controlled studies with or without caffeine to include in their meta-analysis concerning the efficacy of ephedra. Even with the small number of studies included, the researchers felt confident to conclude that there is not enough evidence to support the claim that ephedra enhances athletic performance. Other reviews of ephedra and athletic performance confirm this conclusion as well [8691104]. Most studies have found claims of weight loss to be substantiated [101103]. Again, many of these studies involve a synergistic relationship between ephedra and caffeine.

As ephedra has been indicated for weight loss, it is a tempting supplement to the female athlete concerned about body composition. Ephedrine abuse has been reported in female weight lifters [4]. Gruber and Pope [4] interviewed 64 competitive female body builders in regard to ephedrine usage. Of the 64 women interviewed, 36 reported daily usage of ephedrine for at least a year with many reporting usage for 5–10 years. The most reported dosage was around 120 mg/d; however, there seems to be an acclimation effect and the women reported having to increase dosages or develop more frequent dosing schedules in order to maintain the same effects. While the authors of this study did not assess body composition, 17 % of the female body builders using ephedrine did report having the occurrence of at least one bone fracture. Several of the women also reported amenorrhea and a history of eating disorders. Loss of body fat was the reason given for ephedrine abuse by 35 of the 36 body builders. Reasons for continued use despite the side effects were to reduce the symptoms of withdrawal (i.e., fatigue or weight gain) [4].

Even after the ephedrine ban, NCAA athletes still report taking ephedrine [10]. In 2009, lacrosse and volleyball were the sports with the highest reported usage of ephedrine (1.9 and 1.7 %, respectively). Female athletes in other sports surveyed also reported ephedrine usage after the ban; however, the occurrence of use was less than 1 % [10]. Over 7,800 women were included in this study and the percent of ephedrine use for all female sports combined was 0.9 % or about 70 athletes. Sports surveyed included basketball, field hockey, golf, lacrosse, soccer, softball, swimming, tennis, track, and volleyball [10]. While the number of users seems relatively small, it is important to remember that each of the reported ephedrine users is subject to some very serious side effects. There may also be users who are reluctant to admit usage since ephedrine is a banned substance or because it is packaged in an herbal remedy and the athlete is unaware of its presence. Reported side effects of ephedra are summarized in Table 30.3. Additionally ephedra has also been linked to several deaths [48692101104105].

Table 30.3

Side effects of ephedra

Headache

Tremors

Hypertension

Arrhythmias

Insomnia

Nervousness

Increased heart rate

Sources: Calfee R, Fadale P. Popular ergogenic drugs and supplements in young athletes. Pediatrics. 2006;117(3):e577–e589. Gruber, AJ. and Pope Jr, HG. Ephedrine abuse among 36 female weightlifters. Am J Addict. 1998; 7: 256–261. Powers ME. Ephedra and its application to sport performance: another concern for the athletic trainer? J Athletic Training. 2001;36(4):420–424

When ephedra was banned in 2004, a product by the common name of bitter orange took its place as a fat-burning agent. Bitter orange (Citrus aurantium) contains synephrine and has similar effects as ephedra. It is also used in combination with caffeine [2091]. The National Institute for Health (NIH) advises caution when consuming supplements containing bitter orange as the side effects are similar to ephedra. Synephrine is currently banned by NCAA and the World Anti-Doping Agency (WADA).

If your athlete wants to take an OTC sinus congestion product, advise them to read the packaging for ephedrine and pseudoephedrine. These products will likely be behind the pharmacy counter even though they are an OTC. Both of these ingredients are currently on the banned substance list for NCAA and WADA. Decongestant products available on store shelves contain phenylephrine, which is currently (2012) not banned by NCAA or WADA. As the banned substance list is constantly being updated, you and your athlete need to consult the list for currently allowed decongestants.

30.3.3.4 Caffeine

Caffeine is widely used by athletes and nonathletes for various reasons. Varsity females listed enhanced performance, more energy, alertness, and taste as reasons why they take caffeine. Athletes generally consume their caffeine via beverages such as coffee, tea, or soda. It is also consumed in caffeine tablets, energy bars, and even chocolate [1]. Many energy drinks and gels contain caffeine. Caffeine is allowed up to a certain quantity by the NCAA and WADA. You should advise your athlete to read the current guidelines regarding the amount of caffeine allowed by these agencies and the amount of caffeine in the products they ingest.

Caffeine’s main mode of action is due to its structure. The chemical structure resembles adenosine and will bind to adenosine receptors. Caffeine also stimulates the release of epinephrine [91]. Caffeine has also been reported to enhance fat oxidation and spare muscle glycogen. It is widely consumed although it is not necessary for metabolic functions. People who consume caffeine regularly may become habituated to it and the physiological effects will be blunted. These subjects would also be classified as nonresponders.

One important question asked by athletes was how does caffeine tablet ingestion differ from drinking coffee [1]. While coffee does contain caffeine, it also contains many other compounds which form more metabolites in the body [106107]. Coffee has also shown some ergogenic effects, just not to the same magnitude as ingesting caffeine alone [106]. Coffee would have to be consumed in large amounts to equal the caffeine typically found in tablets. When answering the athletes’ question of coffee or tablets, coffee would most likely result in less of an ergogenic effect unless the subject was naïve to caffeine.

High-Intensity Exercise

During high-intensity exercise, caffeine could lower the rate of RPE and increase glycolytic activity performance. Conversely, caffeine is also associated with an increase in blood lactate [108]. However, not all anaerobic studies are in agreement. Greer et al. [109] found no ergogenic effect or increase in blood lactate of subjects studied when performing the Wingate test.

Strength

The effect of caffeine on strength activities is not conclusive. Previous studies have suggested caffeine may have a direct mode of action on muscle function. This proposed mode of action suggests that caffeine causes the sarcoplasmic reticulum to release more calcium, allowing the muscle to sustain force production for a longer period [106107109].

Endurance

Endurance exercise and caffeine have been studied extensively. The main concept is that caffeine causes fatty acid mobilization and glycogen sparing [106107]. Many of the studies investigating glycogen sparing were not designed to cause sufficient glycogen depletion with or without caffeine. It is unlikely that the ergogenic effects of caffeine on endurance exercise are due to glycogen sparing [106107]. Likewise, research has not supported the theory of caffeine-enhanced fatty acid oxidation during exercise. While many studies report no decrease in RER with caffeine and exercise, caffeine does promote lipolysis at rest [106]. It is clear that caffeine does prolong endurance exercise. The mechanism behind that is not clear. Graham [106] suggests more future research to explore alternative hypotheses.

Adverse Effects

It is often suggested that caffeine usage will result in dehydration. Caffeine is a mild to moderate diuretic. Its effect is seen mainly at rest. Studies have found no effects of caffeine and dehydration after prolonged exercise so long as athletes are replacing fluids adequately [106107]. During prolonged exercise epinephrine-induced renal vasoconstriction causes blood flow to be diverted from the kidneys to the exercising muscle [107]. The diuretic effect of caffeine is minimized during exercise.

Other side effects of caffeine include tachycardia with exercise, increased blood pressure, gastrointestinal distress, and habituation/addiction to caffeine [106107]. There are also side effects associated with discontinuing caffeine usage. Headache, fatigue, and possible flu-like symptoms may occur [106107]. Combining caffeine with ephedra (Ma Huang) is potentially dangerous and should be avoided [101107]. Caffeine also inhibits the ergogenic effect of creatine [86106].

Dosage

For endurance exercise, 3–5 mg/kg is sufficient to produce an ergogenic effect. Since many beverages are variable in the amount of caffeine they contain, tablets are probably the most effective way to get the dosage required to get an ergogenic effect [107]. Sport gels are also available with caffeine added. Athletes should read the packaging to know if they are buying a sport gel with or without caffeine prior to injecting these subjects.

30.3.3.5 Energy Drinks

Most energy drinks contain sugar, caffeine (derived from guarana), taurine, and ginseng. Some energy drinks may also contain B vitamins. Energy drinks contain a unique combination of these ingredients and may contain other substances as well. It is important that athletes consult the allied health professionals with the drink they chose to consume. The allied health professional should inform the athlete about the ingredients in the beverage and the effect of energy drinks on sports performance. Currently there are not many well-controlled studies examining the effects of energy drinks on performance. It is difficult to perform studies using all different brands of energy drinks since the market keeps on growing. However, there are a few well-controlled studies examining the effects of a representative major brand energy drink on exercise endurance and sprint performance.

The Effects of Energy Drinks on Sprint Performance and High-Intensity Exercise

Astorino et al. [110] examined the effects of acute consumption of the energy drink Red Bull on sprint performance in female collegiate soccer players. Soccer players were asked to drink either one can of Red Bull or the equivalent amount of the placebo beverage 1 h before performing multiple t-tests. t-tests were performed as all-out sprints in three bouts of 8 t-tests. Heart rate was monitored with a chest strap HR monitor. There were no differences between the placebo and Red Bull in regard to the RPE, HR, or sprint times. The researchers concluded that a single serving of an energy drink does not provide the female athlete with any ergogenic benefit [110].

Similar results were found when sugar-free Red Bull was given to physically active male and female college students (Mean VO2max 45.41 ± 6.3 ml/kg/min) before performing a run to exhaustion test [111]. Participants consumed either a placebo beverage or a sugar-free Red Bull 60 min prior to a run to exhaustion treadmill test at 80 % VO2max. Trials were separated by 1 week. Run time to exhaustion was not significantly different between either group nor was RPE. Blood lactate levels were significantly elevated postexercise in both trials, but there were no differences between groups of subjects. The consumption of sugar-free Red Bull did not influence substrate utilization during this high-intensity run to exhaustion in physically active college-aged males and females [111].

The Effects of Energy Drinks on Endurance Performance

The effect of an energy drink on endurance performance was examined by Ivy et al. [112]. Participants were male and female competitive cyclists (VO2max 54.9 ± 2.3 ml/kg/min). The dosage for the energy drink was determined by the amount of caffeine needed to elicit an ergogenic effect. Participants consumed the equivalent of two cans of Red Bull (500 ml) or placebo 40 min prior to exercise. A time trial was performed on the cycle at 70 % watt max, 90 rpm for approximately 1 h. On average, participants improved their performance 4.7 % in the treatment group. By 50 min of exercise, HR was elevated above the placebo group (173 ± 4.0 to 166.5 ± 5.8 bpm, respectively) and remained elevated at completion of the exercise session (172.2 ± 4.3 to 170.5 ± 5.7 bpm, respectively). Epinephrine was elevated above the placebo group at 30 min (461.0 ± 122.5 to 195.6 ± 43.8 pg/ml, respectively), 50 min (470.8 ±96.9 to 219.5 ± 293.9 pg/ml, respectively), and after completion of exercise (1,011.8 ± 295.1 to 287.1 ± 69.7, respectively). Norepinephrine, cortisol, and B-endorphin were not different between the two treatment groups. There was also no difference in RPE. Blood lactate levels in the treatment group were elevated pre-exercise and remained elevated over the treatment group for the duration of the exercise. Except for the immediate period before exercise, blood glucose levels did not differ between groups. Glucose levels were significantly higher in the energy drink group prior to exercise (p < 0.05). Insulin levels were also elevated pre-exercise and also at 10 min into the exercise session in the energy drink group. Blood glycerol levels increased with longer exercise duration in both groups. Glycerol levels were significantly higher in the placebo group at 10 min (p < 0.05). No other time points were significantly different for glycerol values. Free fatty acids were significantly increased from 10 to 50 min of exercising in the placebo group (p < 0.05). After completion of exercise, there was no difference between either group in terms of free fatty acids. Substrate utilization, as determined from VO2 and RER data, did not differ between the two groups. In general, carbohydrate usage declined with larger exercise duration and fat usage increased. The researchers demonstrated a nonsignificant trend (p < 0.09) where carbohydrate usage in the energy drink group was higher than the placebo group from 30 to 50 min of exercising. The main finding of this study is that 500 ml of an energy drink containing a combination of caffeine, carbohydrates, taurine, and B vitamins can improve cycling performance in a 1 h time trial. The amount of caffeine in this study was towards the lower end of the range where caffeine has been shown to be effective (2.35 mg/kg body weight); therefore, the researchers speculate that the effects are due to the combination of ingredients in the energy drink. Increased epinephrine levels were likely elevated in response to the caffeine and could have spared muscle glycogen levels and allow for the increasing trend (p < 0.09) of carbohydrate utilization the second half of the exercise [112]. It should be noted that participants consumed energy drink before exercise and consumed water during exercise in a climate-controlled laboratory. Athletes should be aware that results of the same energy drink could be different in outdoor race conditions when climate and nourishment can also affect exercise. Athletes should also be cautioned about the increased HR that consumption of an energy drink may cause and the dangers of cardiac drift in a hot and humid climate.

Kazemi et al. [113] examined the effects of two different taurine-containing energy drinks on time to exhaustion in field volleyball female athletes. The energy drinks compared were Phantom energy drink and Dragon energy drink produced in Austria. Phantom contained carbohydrate, caffeine, taurine, and a mixture of B vitamins. Dragon contained carbohydrate, protein, caffeine, no taurine, and a mixture of B vitamins. Participants consumed either a placebo or an energy drink (6 ml/kg body weight) 40 min prior to exercising. The exercise tests consisted of Bruce treadmill test performed four days apart for each trial. VO2max was increased in both the Phantom and Dragon energy drinks (6.9 and 4.8 %, respectively, p < 0.003) over the placebo trial. Time to exhaustion was also increased in both drinks compared to placebo (Phantom 9.3 % and Dragon 6.5 %, p < 0.003). Energy drinks also decreased RPE (Phantom −4.5 % and Dragon −5.8 %, p < 0.37). There were no significant differences between the two energy drinks. The Dragon energy drink increased postexercise HR above the placebo group (2.2 % <0.019) and Phantom (1.3 %, p < 0.024). There was no difference between Phantom and placebo in regard to HR. Phantom contained more caffeine than Dragon and also contained taurine; however Dragon increased HR compared to Phantom [113]. Neither energy drink contained as much caffeine as Red Bull.

Conclusion: Are Energy Drinks Ergogenic?

Not all types of exercise show improvement in performance upon ingesting energy drinks. Repeated sprint performance did not improve with consumption of an energy drink while endurance exercise appears to benefit. One important feature of these studies is that all of the studies had the participants consume the beverage 40–60 min prior to exercise but did not consume the beverage during exercise. Most studies consume one beverage, not multiple beverages. These studies were also conducted in climate-controlled labs.

The evidence regarding ergogenic effects of energy drinks is still an emerging field. The allied health professional should routinely scan the literature for new research on this front and also look on retail shelves to see what new drinks are being marketed. Become familiar with the ingredients and the amounts of the ingredients. Know the target audience they are marketed to. With regard to safety of energy drinks, there have been reports of cardiac events and/or death with consumption of energy drinks and exercise. However, there are also reports of exercise without elevated HR and improved performance.

30.3.4 Anabolic-Androgenic Steroids

Anabolic-androgenic steroids (AAS) are synthetic derivatives of testosterone [888114]. Adolescent female athlete steroid usage is reported to be between 2 and 5 % [89]. Collegiate usage may be even higher [114].

Women have considerably less testosterone than men, about 10 % that of men [114]. AAS act beneficially on the athlete in three ways: anabolism, anticatabolism, and promoting aggression [88688114]. Testosterone and AAS bind to androgen receptors inside the cytoplasm and are transported to the nucleus. This stimulates an increase in mRNA transcription and leads to increased synthesis of structural and contractile proteins [886114]. It is widely reported that testosterone leaves few androgen receptors open for AAS to attach to and therefore AAS posses an indirect anticatabolic effect. This is thought to be accomplished by displacing glucocorticoids from their receptor sites [88688]. A recent review by Evans suggests this may not always be the case. It is possible that the number of androgen receptors is upregulated with AAS usage [114].

The aggression reported by AAS usage is generally deemed beneficial from an athletic training viewpoint. While this may lead to more intense training, the emotional side effects may not be as beneficial [88688].

Ergogenic effects appear to be limited to muscle hypertrophy and strength gains when performance is concerned along with lean body mass increases [888]. AAS have not been found to produce an ergogenic effect in endurance activities [8]. Steroids have been used to speed up recovery from workouts [114].

30.3.4.1 Adverse Effects

Far outweighing the benefits of AAS are the multiple adverse effects. Many steroid users report experiencing adverse effects [86]. These side effects are different for women than men [8114].

The most notable effects of AAS on women are the virilizing effects: hirsutism, voice deepening, male-pattern baldness, and enlargement of the clitoris. Females may also experience menstrual irregularities and reduced breast size [8114]. Some of these adverse effects are irreversible.

The cardiovascular system is also adversely affected by AAS. Blood pressure increases have been associated with AAS use [86114]. Left ventricular hypertrophy (LVH) was indicated as a side effect also [86]. Since increases in LV wall thickness (and/or increased blood pressure) can be a side effect of chronic athletic training (i.e., heavy resistance training, rowing), this effect may be a cumulative effect of AAS and training routine [115116]. Decreased high-density lipoprotein (HDL) is also associated with steroid usage, although not all studies have reported decreased HDL [88688114].

Other adverse effects include hepatic abnormalities, dermatological problems, and psychological effects. Aggressive behavior is reported frequently along with mood swings. Depression and anger are reported as withdrawal symptoms [88688114].

There are other serious repercussions of AAS usage that are related to injectable steroids, such as boldenone, trenbolone, or stanozolol (ester) [86114]. Injection-related complications include bacterial infection from non-sterile techniques (sharing multidose vials or needles). Hepatitis B, C, and HIV may also be spread this way. Inflammation from repeat use of the same injections site can also occur [114].

30.3.4.2 Dosage

Since AAS are illegal, well-designed controlled studies in athletic performance are lacking. Suffice it to say most steroid users “stack” several anabolic steroid combinations (oral or injectable) in cycles followed by cycles of nonuse for a washout period [886114].

30.3.5 Multivitamins

Information on vitamin and mineral requirements can be found in Appendices for Chap.​ 29 and specific needs for populations have been discussed in Chaps. 282931, and 32. The focus of this section is the reasons why female athletes take multivitamins, iron, and calcium.

When surveyed, multivitamins were in the top 5 of dietary supplements taken by female athletes [13]. The reasons females gave for using multivitamins were as follows: “recommended by family, friends, coaches or trainers, to meet nutritional needs, boost the immune system and prevent disease, boost energy, alertness, and habit from childhood” [12117]. While both male and female athletes report taking multivitamins with minerals, female athletes are more likely to take iron and calcium supplements than their male counterparts [117].

However, not all multivitamins are just that—a multivitamin. Several multivitamins contain herbal extracts (phyto-extracts), soy proteins, BCAAs, ginseng, and Ginkgo biloba, to name a few. These are usually marketed as a multivitamin labeled for performance and are widely available on drugstore shelves or health marts.

It is important to remember that multivitamins fall under the dietary supplement category and are not subject to FDA regulation. Allied health professions who work with athletes and coaches should be aware of the brand their athletes are taking and be able to counsel them to make informed purchases and encourage them to read labels. As an alternative, there are several prescription vitamins which are subject to FDA regulations that could be prescribed by the team physician.

30.3.6 Iron

Women in general tend to have more iron deficiency issues than men [118119]. Menstrual blood loss varies by woman and can be underestimated in women with heavier cycles. Other factors include inadequate dietary intake, increased loss from sweat, or gastrointestinal blood loss in runners [118119].

Iron status should be determined by plasma ferritin. Normal levels vary, but <35 μg/L are below normal [118]. Even slight anemia in athletes will negatively impact performance [119]. If athletes are borderline, low normal, or below normal, iron supplementation may be prudent. As iron comes in different forms, which are absorbed differently, and is unregulated on the store shelf, it could be more beneficial to have the team physician prescribe iron. A multivitamin with iron could be a good choice.

30.3.6.1 Supplementing Iron with Normal Ferritin Levels

High dose of over-the-counter (OTC) iron supplements can cause gastrointestinal distress or constipation, both of which would prove to be ergolytic to athletic performance [119]. In addition, studies of iron supplementation in non-anemic athletes have not shown improvement in performance [118].

30.3.7 Calcium

Calcium should be consumed in the diet as should other nutrients. Most female athletes choose to take a calcium supplement to strengthen bones, due to lactose intolerance or low dietary intake [12]. Calcium supplementation may also be considered if the athlete is consuming high amount of protein. Increased dietary protein may produce a lower urinary pH and an increase in calcium excretion [120]. Increased calcium intake may offset the increased protein-induced urinary excretion of calcium [121].

Typically calcium/protein ratio of 20:1 is recommended for middle-aged women [122]. This ratio is most likely different for an athlete as dietary protein requirement is elevated to maintain a positive nitrogen balance.

30.4 Contemporary Understanding of the Issues

Female athletes are consuming supplements for a variety of reasons:

·               Health

·               Inadequate diet

·               Body composition

·               Improved performance

·               Increased “energy”

When choosing protein supplements, the athlete needs to understand the properties of protein sources: whey, casein, and soy. Whey is absorbed at the fastest rate followed by soy and then casein. The quick absorption rate yields a rapid but transient increase in muscle protein synthesis while a slower rate tends to mediate protein catabolism. A protein supplement utilizing a mixture of sources would be preferred. It should be noted that both whey and casein are animal-derived protein sources. Should you work with a vegetarian athlete, they should be made aware of the importance of complete proteins and EAAs.

30.5 Future Directions

Studies examining protein supplementation have been primarily conducted on male participants. Future research should focus on the female population. Sex hormones affect protein metabolism. Without studies focusing on the effects of muscle formation and performance in females, we can only suggest general guidelines for protein supplementation. This is also the case for EAA and BCAA supplementation.

Echinacea is a popular supplement for boosting the immune system. Studies conflict as to the efficacy of Echinacea to prevent or shorten a cold. Furthermore, Echinacea supplementation has been linked to improved VO2maxthrough increased EPO. This increase was not accompanied by an increase in RBC. Typically, treatments increasing EPO increase RBC. This can lead to cardiovascular complications. Further research is needed to determine the safety of using Echinacea to increase VO2max and determine if Echinacea can effectively treat a cold.

30.6 Concluding Remarks

It is of the utmost importance that allied health professionals and coaches who work with female athletes be familiar with the ergogenic aids female athletes are likely to use and the products that may contain them. Athletes will be more inclined to discuss supplements and seek your advice if you address them with an open mind and explain the pros and cons. Many athletes list family and other athletes as major sources of information on supplements [2]. Herbold et al. [3] reported family was the first source athletes went to regarding supplements (53 %). Other sources of information included friends (24.6 %), physician (18.7 %), coaches (10.5 %), and nutritionist (8.2 %) [3].

When surveyed, athletes indicated they do not use a certain supplement and usually list a product containing it under the “other” category [2]. This demonstrates that athletes lack knowledge of supplements, regulations, and how to read labels.

Finally, a supplement may be legal for OTC sales but illegal in certain competitions, or a supplement may be contaminated with substances not listed on the label. It is also important that the athletes know they are responsible for what they put in their bodies whether or not it is on the label and will result in a failed drug test.

On average, 15 % of nonhormonal nutritional supplements are contaminated with anabolic steroids [123]. Contamination has been found in products from many different countries. This may be due to lack of cleaning on the production line between manufacturing prohormones and nutritional supplements (i.e., vitamins, minerals, proteins, creatine). It may also be due to cross-contamination from shipping containers of raw materials. Some supplements available are faked supplements (steroids not listed on the label or given fake names) intentionally produced with high amounts of anabolic steroids normally available by prescription. The same manufacturers of faked supplements may also manufacture other nutritional supplements again leading to contamination. Anabolic steroids found in contaminated substances have been found to contain metandienone, stanozolol, boldenone, oxandrolone, dehydrochloromethyl-testosterone, and clenbuterol. Even some supplements marketed for weight loss have been found to contain clenbuterol. In as little as 3 h after ingestion of a clenbuterol-contaminated weight-loss product, clenbuterol was detectable in the urine (2 ng/ml) [123].

The allied health team should be aware of the regulations regarding banned substances for the governing body of athletes such as International Olympic Committee (IOC), WADA, and/or the NCAA. The team may also want to access http://​www.​naturaldatabase.​com. The Natural Medicines Comprehensive Database is a good resource for evidence-based information on nutritional supplements that is not biased from advertising sponsorship.

References

1.

Kristiansen M, Levy-Milne R, Barr S, Flint A. Dietary supplement use by varsity athletes at a Canadian University. Int J Sport Nutr Exerc Metab. 2005;15(2):195–210.PubMed

2.

Froiland K, Koszewski W, Hingst J, Kopecky L. Nutritional supplement use among college athletes and their sources of information. Int J Sport Nutr Exerc Metab. 2004;14(1):104–20.PubMed

3.

Herbold NH, Visconti BK, Frates S, Bandini L. Traditional and nontraditional supplement use by collegiate female varsity athletes. Int J Sport Nutr Exerc Metab. 2004;14(5):586–93.PubMed

4.

Gruber AJ, Pope HG. Ephedrine abuse among 36 female weightlifters. Am J Addictions. 1998;7(4):256–61.

5.

Ziegler PJ, Nelson JA, Jonnalagadda SS. Use of dietary supplements by elite figure skaters. Int J Sport Nutr Exerc Metab. 2003;13(3):266–76.PubMed

6.

Whitehead MT, Martin TD, Scheett TP, Webster MJ. Running economy and maximal oxygen consumption after 4 weeks of oral echinacea supplementation. J Strength Cond Res. 2012;26(7):1928.PubMed

7.

Whitehead MT, Martin TD, Scheet TP, Webster MJ. The effects of 4 wk of oral echinacea supplementation on serum erythropoietin and indices of erythropoietic status. Int J Sport Nutr Exerc Metab. 2007;17(4):378–90.PubMed

8.

Congeni J, Miller S. Supplements and drugs used to enhance athletic performance. Pediatr Clin North Am. 2002;49(2):435–61.PubMed

9.

Faigenbaum AD, Zaichkowsky LD, Gardner DE, Micheli LJ. Anabolic steroid use by male and female middle school students. Pediatrics. 1998;101(5):E6.PubMed

10.

NCAA publications—research—substance use—national study of substance use trends among NCAA college student-athletes. Cited 7/31/2012. Available from: http://​www.​ncaapublications​.​com/​p-4266-research-substance-use-national-study-of-substance-use-trends-among-ncaa-college-student-athletes.​aspx

11.

Yusko DA, Buckman JF, White HR, Pandina RJ. Alcohol, tobacco, illicit drugs, and performance enhancers: a comparison of use by college student athletes and nonathletes. J Am Coll Health. 2008;57(3):281–90.PubMedPubMedCentral

12.

ACSMps. Nutrition and athletes performance. Med Sci Sports Exerc 2009;41(3):709–31.

13.

Campbell B, Kreider RB. Conjugated linoleic acids. Curr Sports Med Rep. 2008;7(4):237–41.PubMed

14.

Layman DK, Shiue H, Sather C, Erickson DJ, Baum J. Increased dietary protein modifies glucose and insulin homeostasis in adult women during weight loss. J Nutr. 2003;133:405–10.PubMed

15.

Volek JS, Forsythe C. Very-low carbohydrate diets, chapter 25. In: Antonio J, Kalman D, Stout JR, Greenwood M, Willoughby DG, Haff GG, editors. Essentials of sports nutrition and supplements. Totowa, NJ: Humana Press; 2008. p. 581–603.

16.

Clifton PM, Keogh JB, Noakes M. Long-term effects of a high-protein weight-loss diet. Am J Clin Nutr. 2008;87(1):23.PubMed

17.

Noakes M. The role of protein in weight management. Asia Pac J Clin Nutr. 2008;17:169–71.PubMed

18.

Bilsborough S, Mann N. A review of issue of dietary protein intake in humans. Int J Sports Nutr Exc Metab. 2006;16:129–52.

19.

BØrsheim E, Tipton K, Wolfe SE, Wolfe RR. Essential amino acids and muscle protein recovery from resistance exercise. Am J Physiol Endocrinol Metab. 2002;283:E648–57.PubMed

20.

Paddon-jones D, Sheffield-Moore M, Zhang XJ, Volpi E, Wolf SE, Aarslan A, et al. Amino acid ingestión improves muscles protein síntesis. Am J Physiol Endocrinol Metab. 2004;286:E321–8.PubMed

21.

Tipton KD, Wolf R. Exercise, protein metabolism and muscle growth. Int J Sports Nutr Exc Metab. 2001;11(1):109–32.

22.

Kreider RB, Wilborn CD, Taylor L, Campbell B, Almada AL, Collins R, et al. ISSN exercise & sport nutrition review: research & recommendations. J Int Soc Sports Nutr. 2010;7:7.PubMedPubMedCentral

23.

Bianco A, Mammina C, Paoli A, Bellafiore M, Battaglia G, Caramazza G, et al. Protein supplementation in strength and conditioning adepts: knowledge, dietary behavior and practice in palermo, Italy. J Int Soc Sports Nutr. 2011;8:25.PubMedPubMedCentral

24.

Petroczi A, Naughton DP, Mazanov J, Holloway A, Bingham J. Performance enhancement with supplements: incongruence between rationale and practice. J Int Soc Sports Nutr. 2007;4(19):19.PubMedPubMedCentral

25.

Imdad A, Bhutta ZA. Effect of balanced protein energy supplementation during pregnancy on birth outcomes. BMC Publ Health. 2011;11 Suppl 3:S17.

26.

Etzel MR. Manufacture and use of dairy protein fractions. J Nutr. 2004;134:996S–1002.PubMed

27.

Hoffman JR, Falvo MJ. Protein- which is the best? J Sports Sci Med. 2004;13:118–30.

28.

Snyder BS, Haub MD. Whey, casein, and soy proteins. In: Driskell JA, editor. Sports nutrition fast and proteins. Boca Raton, FL: CRC Press; 2007. p. 143–63.

29.

Marshall K. Therapeutic applications of whey protein. Altern Med Rev. 2004;9(2):136–56.PubMed

30.

Miller AL. Therapeutic considerations of L-glutamine: a review of the literature. Altern Med Rev. 1999;4(4):239.PubMed

31.

McConell GK, Kingwell BA. Does nitric oxide regulate skeletal muscle glucose uptake during exercise? Exerc Sport Sci Rev. 2006;34(1):36–41.PubMed

32.

Stipanuk M, Stipanuk H. Role of the liver in regulation of body cysteine and taurine levels: a brief review. Neurochem Res. 2004;29(1):105–10.PubMed

33.

Mojtahedi MC, Thorpe MP, Karampinos DC, Johnson CL, Layman DK, Georgiadis JG, et al. The effects of a higher protein intake during energy restriction on changes in body composition and physical function in older women. J Gerontol Ser A Biol Sci Med Sci. 2011;66(11):1218.

34.

Holm L, Olesen JL, Matsumoto K, Doi T, Mizuno M, Alsted TJ, et al. Protein-containing nutrient supplementation following strength training enhances the effect on muscle mass, strength, and bone formation in postmenopausal women. J Appl Physiol. 2008;105(1):274–81.PubMed

35.

Koopman R. Dietary protein and exercise training in ageing. Proc Nutr Soc. 2011;70(1):104–13.PubMed

36.

Tipton K, Elliott TA, Cree MG, Wolf SE, Sanford AP, Wolfe RR. Ingestion of casein and whey proteins result in muscle anabolism after resistance exercise. Med Sci Sports Exc. 2004;36(12):2073–81.

37.

Paul GL. The rationale for consuming protein blends in sports nutrition. J Am Coll Nutr. 2009;28(Suppl):464S.PubMed

38.

Boirie Y, Dangin M, Gachon P, Vasson M, Maubois J, Beaufrère B. Slow and fast dietary proteins differently modulate postprandial protein accretion. Proc Natl Acad Sci U S A. 1997;94(26):14930–5.PubMedPubMedCentral

39.

West DWD, Burd NA, Coffey VG, Baker SK, Burke LM, Hawley JA, et al. Rapid aminoacidemia enhances myofibrillar protein synthesis and anabolic intramuscular signaling responses after resistance exercise. Am J Clin Nutr. 2011;94(3):795.PubMed

40.

Hasler CM. The cardiovascular effects of soy products. J Cardiovasc Nurs. 2002;16(4):50.PubMed

41.

Zhan S, Ho SC. Meta-analysis of the effects of soy protein containing isoflavones on the lipid profile. Am J Clin Nutr. 2005;81(2):397.PubMed

42.

Laguer A. Supplements soy. [Internet]. 2003 [cited] (20/12/2006). Available from: http://​www.​ucdenver.​edu/​academics/​colleges/​pharmacy/​Resources/​OnCampusPharmDSt​udents/​ExperientialProg​ram/​Documents/​nutr_​monographs/​Monograph-soy.​pdf

43.

Skidmore-Roth L. Mosby’s handbook of herbs & natural supplements. 1st ed. St. Louis, MO: Elsevier; 2001.

44.

Cook M, Cribb PJ. Effective nutritional supplement combinations chapter 9. In: Greenwood M, Kalman DS, Antonio J, editors. Nutritional supplements in sports and exercise. Totowa, NJ: Humana Press; 2008. p. 259–319.

45.

Cribb PJ, Williams AD, Hayes A. A creatine-protein-carbohydrate supplementation enhances responses to resistance training. Med Sci Sports Exc. 2007;39(11):1960–8.

46.

Dangin M, Guillet C, Garcia-Rodenas C, Gachon P, Bouteloup-Demange C, Reiffers-Magnani K, et al. The rate of protein digestion affects protein gain differently during aging in humans. J Physiol. 2003;549(Pt 2):635–44.PubMedPubMedCentral

47.

Dangin M, Boirie Y, Guillet C, Beaufrère B. Influence of the protein digestion rate on protein turnover in young and elderly subjects. J Nutr. 2002;132:3228S–33.PubMed

48.

Pennings B, Boirie Y, Senden J, Gijsen AP, Kuipers H, van Loon L. Whey protein stimulates postprandial muscle protein accretion more effectively than do casein and casein hydrolysate in older men. Am J Clin Nutr. 2011;93(5):997–1005.PubMed

49.

Tang JE, Moore DR, Kujbida GW, Tarnopolsky MA, Phillips SM. Ingestion of whey hydrolysate, casein, or soy protein isolate: effects on mixed muscle protein synthesis at rest and following resistance exercise in young men. J Appl Physiol. 2009;107(3):987–92.PubMed

50.

Moore RD, Robinson MJ, Fry JL, Tang JE, Glover EI, Wilkinson SB, et al. Ingested protein dose response of muscle and albumin protein synthesis after resistance exercise in young men. Am J Clin Nutr. 2009;89:161–8.PubMed

51.

Tarnopolsky MA, Timmons BW. Protein: quantity and quality, chapter 7. In: Driskell JA, editor. Sports nutrition fats and proteins. Boca Raton, FL: CRC Press; 2007. p. 109–42.

52.

Lamont LS, McCullough AJ, Kalhan SC. Gender differences in leucine, but not lysine, kinetics. J Appl Physiol. 2001;91(1):357.PubMed

53.

Lamont LS, McCullough AJ, Kalhan SC. Gender differences in the regulation of amino acid metabolism. J Appl Physiol. 2003;95(3):1259–65.PubMed

54.

Young VR, Tharakan JJ. Nutritional essentiality of amino acids and amino acid requirements in healthy adults in clinical nutrition. In: Cynober LC, editor. Metabolic and therapeutic aspects of amino acids in clinical nutrition. 2nd ed. Boca Raton, FL: CRC Press; 2004. p. 439–70.

55.

Wilkinson SB, Tarnopolsky MA, Macdonald MJ, Macdonald JR, Armstrong D, Phillips SM. Consumption of fluid skim milk promotes greater muscle protein accretion after resistance exercise than does consumption of an isonitrogenous and isoenergetic soy- protein beverage. Am J Clin Nutr. 2007;85(4):1031.PubMed

56.

Dillon EL, Sheffield-Moore M, Paddon-Jones D, Gilkison C, Sanford AP, Casperson SL, et al. Amino acid supplementation increases lean body mass, basal muscle protein synthesis, and insulin-like growth factor-I expression in older women. J Clin Endocrinol Metab. 2009;94(5):1630–7.PubMedPubMedCentral

57.

Wolfe RR. Regulation of muscle protein by amino acids. J Nutr. 2002;132:3219S–24.PubMed

58.

Cribb PJ, Hayes A. Effects of supplement timing and resistance exercise on skeletal muscle hypertrophy. Med Sci Sports Exc. 2006;38(11):918–1925.

59.

La Bounty PM, Campbell BI, Wilson J, Galvan E, Berardi J, Kleiner SM et al. International society of sports nutrition position stand: meal frequency. J. Int. Soc. Sports. Nutr. 2011;8(4):1–12.

60.

Willoughby DS, Stout JR, Wilborn CD. Effects of resistance training and protein plus amino acid supplementation on muscle anabolic, mass, and strength. Amino Acids. 2007;32:467–77.PubMed

61.

Breen L, Phillips SM. Skeletal muscle protein metabolism in the elderly: Interventions to counteract the “anabolic resistance” of ageing. Nutr Metab. 2011;8:68.

62.

Yang Y, Breen L, Burd NA, Hector AJ, ChurchwardVenne TA, Josse AR, et al. Resistance exercise enhances myofibrillar protein synthesis with graded intakes of whey protein in older men. Br J Nutr. 2012;108(10):1780–8.PubMed

63.

Bohe J, Low A, Wolfe RR, Rennie MJ. Human muscle protein synthesis is modulated by extracellular, not intramuscular amino acid availability: a dose-response study. J Physiol. 2003;552(Pt 1):315–24.PubMedPubMedCentral

64.

Figueroa Alchapar J, Naclerio F. Ayudas ergogenicas nutricionales para la actividad fisica y el deporte. In: Naclerio F, editor. Deportivo, fundamentos y aplicaciones en diferentes deportes. Medica Panamericana; 2011. p. 517-37

65.

Kerksick C, Harvey T, Stout J, Campbell B, Wilborn C, Kreider R, et al. International society of sports nutrition position stand: nutrient timing. J Int Soc Sports Nutr. 2008;5:17.PubMedPubMedCentral

66.

Kerksick C, Leutholtz B. Nutrient administration and resistance training. J Int Soc Sports Nutr. 2005;2(1):50–67.PubMedPubMedCentral

67.

Rasmusen CJ. Nutritional supplement for endurance athletes chapter 11. In: Greenwood M, Kalman DS, Antonio J, editors. Nutritional supplements in sports and exercise. Totowa, NJ: Humana Press; 2008. p. 369–407.

68.

Willoughby DS, Rosene JM. Effects of oral creatine and resistance training on myogenic regulatory factor expression. Med Sci Sports Exerc. 2003;35(6):923–9.PubMed

69.

Mourier A, Bigard AX, De Kerviler E, Roger B, Legrand H, Guezennec CY. Combined effects of caloric restriction and branched-chain amino acid supplementation on body composition and exercise performance in elite wrestlers. Int J Sports Med. 1997;18(1):47–55.PubMed

70.

Campbell B, Kreider RB, Ziegenfuss T, La Bounty P, Roberts M, Burke D, et al. International society of sports nutrition position stand: Protein and exercise. J. Int. Soc. Sports. Nutr. 2007;doi:10.​1186/​1550-2783-4-8:​4:​8.

71.

Guoyao W. Intestinal mucosal amino acid catabolism. J Nutr. 1998;128(8):1249–52.

72.

Meeusen R, Watson P, Dvorak J. The brain and fatigue: new opportunities for nutritional intervention? J Sports Sci. 2006;24(7):773–82.PubMed

73.

Newsholme EA, Leech AR. Biochemical for the medical sciences. New York: Wiley; 1994.

74.

Newsholme EA, Blomstrand E. Branched-chain amino acids and central fatigue. J Nutr. 2006;136:274S–6.PubMed

75.

Shimomura Y, Inaguma A, Watanabe S, Yamamoto Y, Muramatsu Y, Bajotto G, et al. Branched-chain amino acid supplementation before squat exercise and delayed-onset muscle soreness. Int J Sport Nutr Exerc Metab. 2010;20(3):236–44.PubMed

76.

Shimomura Y, Yamamoto Y, Bajotto G, Sato J, Murakami T, Shimomura N, et al. Nutraceutical effects of branched-chain amino acids on skeletal muscle. J Nutr. 2006;136(2):529S.PubMed

77.

Antonio H, Sanders M, Kalman D, Woodgate D, Street C. The effects of high dose glutamine ingestion on weightlifting performance. J Strength Cond Res. 2002;16(1):157–60.PubMed

78.

Walsh NP, Blannin AB, Bishop NC, Robson PJ, Robson S, Gleeson M. Effect of oral glutamine supplementation on human neutrophil lipopolysa-ccharide-stimulated degranulation following prolonged exercise. Int J Sports Nutr Exerc Metabol. 2000;10:39–50.

79.

Gibala MJ. Regulation of skeletal muscle amino acid metabolism during exercise. Int J Sports Nutr Exc Metab. 2001;11(1):87–108.

80.

Phillips GC. Glutamine: the nonessential amino acid for performance enhancement. Curr Sports Med Rep. 2007;6(4):265.PubMed

81.

Cuisinier C, Ward RJ, Francaux M, Sturbois X, de Witte P. Changes in plasma and urinary taurine and amino acids in runners immediately and 24 h after a marathon. Amino Acids. 2001;20(1):13–23.PubMed

82.

Lagranha CJ, Levada-Pires A, Sellitti DF, Procopio J, Curi R, Pithon-Curi T. The effect of glutamine supplementation and physical exercise on neutrophil function. Amino Acids. 2008;34(3):337–46.PubMed

83.

Alvares TS, Meirelles CM, Bhambhani YN, Paschoalin V, Gomes P. L-arginine as a potential ergogenic aid in healthy subjects. Sports Med. 2011;41(3):233–48.PubMed

84.

Fricke O, Baecker N, Heer M, Tutlewski B, Schoenau E. The effect of L-arginine administration on muscle force and power in postmenopausal women. Clin Physiol Funct Imaging. 2008;28(5):307–11.PubMed

85.

Karlic H, Lohninger A. Supplementation of L-carnitine in athletes: does it make sense? Nutrition. 2004;20(7–8):709–15.PubMed

86.

Calfee R, Fadale P. Popular ergogenic drugs and supplements in young athletes. Pediatrics. 2006;117(3):e577–89.PubMed

87.

Barr SI, Rideout CA. Nutritional considerations for vegetarian athletes. Nutrition. 2004;20(7–8):696–703.PubMed

88.

Tokish JM, Kocher MS, Hawkins RJ. Ergogenic aids: a review of basic science, performance, side effects, and status in sports. Am J Sports Med. 2004;32(6):1543–53.PubMed

89.

Stevenson SW, Dudley GA. Creatine loading, resistance exercise performance, and muscle mechanics. J Strength Cond Res. 2001;15(4):413–9.PubMed

90.

Vandenberghe K, Goris M, Van Hecke P, Van Leemputte M, Vangerven L, Hespel P. Long-term creatine intake is beneficial to muscle performance during resistance training. J Appl Physiol. 1997;83(6):2055–63.PubMed

91.

Bucci LR. Selected herbals and human exercise performance. Am J Clin Nutr. 2000;72 Suppl 2:624S–36.PubMed

92.

Winterstein AP, Storrs CM. Herbal supplements: considerations for the athletic trainer. J Athl Train. 2001;36(4):425–32.PubMedPubMedCentral

93.

Bahrke MS, Morgan WP, Stegner A. Is ginseng an ergogenic aid? Int J Sport Nutr Exerc Metab. 2009;19(3):298–322.PubMed

94.

Palisin TE, Stacy JJ. Ginseng: is it in the root? Curr Sports Med Rep. 2006;5(4):210.PubMed

95.

Vogler BK, Pittler MH, Ernst E. The efficacy of ginseng. A systematic review of randomised clinical trials. E J Clin Pharmacol. 1999;55(8):567–75.

96.

Engels H. Effects of ginseng supplementation on supramaximal exercise performance and short-term recovery. J Strength Cond Res. 2001;15(3):290–5.PubMed

97.

Dowling EA, Redondo DR, Branch JD, Jones S, McNabb G, Williams MH. Effect of eleutherococcus senticosus on submaximal and maximal exercise performance. Med Sci Sports Exerc. 1996;28(4):482–9.PubMed

98.

Barrett B, Brown R, Rakel D, Mundt M, Bone K, Barlow S, et al. Echinacea for treating the common cold: a randomized trial. Ann Intern Med. 2010;153(12):769.PubMedPubMedCentral

99.

Turner RB, Riker DK, Gangemi JD. Ineffectiveness of echinacea for prevention of experimental rhinovirus colds. Antimicrob Agents Chemother. 2000;44(6):1708.PubMedPubMedCentral

100.

Turner RB, Bauer R, Woelkart K, Hulsey TC, Gangemi JD. An evaluation of echinacea angustifolia in experimental rhinovirus infections. N Engl J Med. 2005;353(4):341.PubMed

101.

Powers ME. Ephedra and its application to sport performance: another concern for the athletic trainer? J Ath Train. 2001;36(4):420–4.

102.

Dietary supplements > guidance for industry: final rule declaring dietary supplements containing ephedrine alkaloids adulterated because they present an unreasonable risk; small entity compliance guide; Cited [7/31/2012]. Available from: http://​www.​fda.​gov/​Food/​GuidanceComplian​ceRegulatoryInfo​rmation/​GuidanceDocument​s/​DietarySupplemen​ts/​ucm072997.​htm

103.

Shekelle PG, Hardy ML, Morton SC, Maglione M, Mojica WA, Suttorp MJ, et al. Efficacy and safety of ephedra and ephedrine for weight loss and athletic performance: a meta-analysis. JAMA. 2003;289(12):1537.PubMed

104.

Juhn MS. Popular sports supplements and ergogenic aids. Sports Med. 2003;33(12):921–39.PubMed

105.

Ahrendt DM. Ergogenic aids: counseling the athlete. Am Fam Physician. 2001;63(5):913–22.PubMed

106.

Graham TE. Caffeine and exercise: metabolism, endurance and performance. Sports Med. 2001;31(11):785–807.PubMed

107.

Mangus BC, Trowbridge CA. Will caffeine work as an ergogenic aid? the latest research. Ath Therapy Today. 2005;10(3):57–62.

108.

Doherty M, Smith P, Hughes M, Davison R. Caffeine lowers perceptual response and increases power output during high-intensity cycling. J Sports Sci. 2004;22(7):637.PubMed

109.

Greer F, McLean C, Graham TE. Caffeine, performance, and metabolism during repeated wingate exercise tests. J Appl Physiol. 1998;85(4):1502.PubMed

110.

Astorino TA, Matera AJ, Basinger J, Evans M, Schurman T, Marquez R. Effects of red bull energy drink on repeated sprint performance in women athletes. Amino Acids. 2012;42(5):1803.PubMed

111.

Candow DG, Kleisinger AS, Grenier S, Dorsch KD. Effect of sugar-free red bull energy drink on high-intensity run time-to-exhaustion in young adults. J Strength Cond Res. 2009;23(4):1271.PubMed

112.

Ivy JL, Kammer L, Ding Z, Wang B, Bernard JR, Liao Y, et al. Improved cycling time-trial performance after ingestion of a caffeine energy drink. Int J Sport Nutr Exerc Metab. 2009;19(1):61.PubMed

113.

Kazemi F, Gaeini A, Kordi A, Rahnama M, Rahnama R, Rahnama N. The acute effects of two energy drinks on endurance performance in female athlete students. Sport Sci Health. 2009;5(2):55–60.

114.

Evans NA. Current concepts in anabolic-androgenic steroids. Am J Sports Med. 2004;32(2):534.PubMed

115.

Pluim BM. Current perspective. the athlete’s heart: a meta-analysis of cardiac structure and function. Circulation. 1999;101(3):336–45.

116.

Whyte GP, George KJ, Nevill AJ, Shave RJ, Sharma SJ, Mckenna WJ. Left ventricular morphology and function in female athletes: a meta-analysis. Int J Sports Med. 2004;25(5):380–3.PubMed

117.

Krumbach CJ, Ellis DR, Driskell JA. A report of vitamin and mineral supplement use among university athletes in a division I institution. Int J Sport Nutr. 1999;9(4):416.PubMed

118.

Nielsen P, Nachtigall D. Iron supplementation in athletes current recommendations. Sports Med. 1998;26(4):207.PubMed

119.

Beard J, Tobin B. Iron status and exercise. Am J Clin Nutr. 2001;72(2):594S.

120.

Barzel US, Massey LK. Excess dietary protein can adversely affect bone. J Nutr. 1998;128(6):1051–3.PubMed

121.

Dawson-Hughes B. Interaction of dietary calcium and protein in bone health in humans. J Nutr. 2003;133(3):852S.PubMed

122.

Heaney RP. Excess dietary protein may not adversely affect bone. J Nutr. 2008;128(6):1054.

123.

Geyer H, Parr MK, Koehler K, Mareck U, Schanzer W, Thevis M. Nutritional supplements cross-contaminated and faked with doping substances. J Mass Spec. 2008;43:892–902.

124.

Reeds PJ. Dispensable and indispensable amino acids for humans. J Nutr. 2000;130(7):1835S.PubMed