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

22. Resistance Training Guidelines for Active Females Throughout the Lifespan: Children, Adolescences, Adult Women, and the Aging Woman

Maria Fernandez-del-Valle  and Tyrel S. McCravens 

(1)

Department of Health, Exercise, and Sport Sciences, Texas Tech University, Exercise and Sport Sciences Building, 3204 Main, Lubbock, TX 49423, USA

(2)

Department of Health, Exercise, and Sport Sciences, Texas Tech University, 2500 Broadway, Lubbock, TX 79409, USA

Maria Fernandez-del-Valle (Corresponding author)

Email: maria.fernandez-del-valle@ttu.edu

Tyrel S. McCravens (Corresponding author)

Email: tyrel.mccravens@ttu.edu

Abstract

Due to recent changes in physical activity practices, strength training, or resistance training, has become an area of focus in the research of determining the overall health of an individual. As individuals age, disorders relating to both bone and muscle begin to cause a decline in health and functional activity. Bone disorders, such as osteoporosis and osteopenia, have been linked to muscle disorders like sarcopenia (a loss of skeletal muscle mass). While these disorders do affect males, females tend to show higher incidences of these diseases. Current research suggests that resistance training can help to delay the effects of these diseases. Resistance training implemented in the early stages of life, such as childhood and adolescence, has been shown to cause increases in both bone growth, specifically bone mass and bone mineral density, and skeletal muscle mass. Resistance training can help maintain current levels of fitness in adults and improve activities of daily living in the elderly. In order to receive maximum benefits from resistance training, guidelines spanning the entire lifespan needed to be developed. The resistance training guidelines cover everything from basic supervision needs to intensity, duration, and frequency of the program. The guidelines include specific directions to increase hypertrophy, power, strength, and endurance. So, resistance training, which was once thought to cause injury in some, is now seen as a way to increase health and even reduce the chance of injury when done properly.

Keywords

Resistance trainingChildrenAdolescencesHypertrophySarcopenia

22.1 Learning Objectives

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

·  Strength as a conditional capacity. Strength: the main capacity?

·  Effects of resistance training in the muscular-skeletal tissue through lifespan

·  How to approach strength training with children and adolescents

·  Resistance training guidelines with children, adolescents, adults, and aging women

·  Resistance training as a preventive factor from injuries and healthy posture in the future

22.2 Introduction

22.2.1 Strength as a Conditional Capacity. Strength: The Main Capacity?

Given the recommendations of several organizations, it is clear an analysis about structures related with the quality of life and health in women of all age ranges is needed. The ability to prescribe accurate exercise programs depends on our knowledge of how different elements are involved in proper muscular-skeletal development and functional capacity performance.

In order to reach maximum oxygen uptake, the pulmonary, cardiovascular, and muscular-skeletal systems all have to function together properly. The cardiopulmonary system has been studied during exercise through the lifespan due to its relationship with performance, quality of life, longevity, and prognosis in chronic diseases [14], while muscular-skeletal tissue has been neglected for decades. However, due to recent changes in habits, new research and field work have contributed to the development of means and methods of training for high-performance athletes, regular practitioners, and patients with chronic pathologies. Strength training (resistance training, or RT) seems to appear as a basis to improve the quality of life, prevent injuries, and enhance an adequate performance. Therefore, strength seems to be the main component of physical fitness (Fig. 22.1) [5].

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Fig. 22.1

Components of physical fitness. Modified from Tous Fajardo J. Entrenamiento de la fuerza en los deportes de equipo. Apuntes del Máster Profesional en Alto Rendimiento en Deportes de Equipo. Barcelona (Spain): Byomedic-Mastercede, Fundación FC Barcelona; 2003

For a better understanding, it is necessary to know how components of physical fitness (strength, endurance, speed, flexibility, and coordination) are interrelated and how their improvements are interdependent. Since early 2000s, the theory of strength as an engine capacity has increased in relevance, and some authors have hypothesized that strength is the fundamental physical capacity. Traditionally, strength has been divided into three types: maximal strength, speed strength (muscular speed/power), and strength endurance (muscular endurance); however, there is a strength which is displayed in different forms. As a result, components such as speed and endurance result in maintenance of strength levels at different intensities and influence coordination and flexibility [57].

“The ability to generate force is necessary for all types of movements” [8]. The cross-sectional area of the muscle is related to the maximal force production, so motor unit recruitment and activation (size principle), fiber angle pennation, muscle length, joint angle, and contraction velocity are all factors that will alter the expression of muscular strength [8].

Strength is considered essential in giving all individuals, from young to old, the ability to perform activities associated with daily living, recreation, and maximal performance. It can also help to prevent injuries and disabilities that may occur throughout the lifespan. Therefore, an improvement in strength levels enhances the development of basic motor skills that facilitate the realization of more specific tasks [79].

22.2.2 Skeletal Muscle: An Organ

Skeletal muscle has recently been considered an organ itself [1011]. This is because of its ability to synthesize and release a wide range of proteins at rest and during exercise, as well as its ability to metabolize carbohydrates (up to 80 %) and fats. In fact, skeletal muscle can also communicate with other tissue (e.g., adipose and bone) and organs (e.g., liver, pancreas, or brain) which can lead to bone, metabolic, and circulatory disease in the absence of regular activity [12].

Skeletal muscle is the largest reserve of protein in the body that supplies amino acids in order to synthesize proteins in other tissues and muscle in absence of nourishment and provides precursors for gluconeogenesis in the liver [13]. In addition, skeletal muscle is the primary site of glucose placement. Diminished muscle mass results in a diminished glucose metabolism related with higher risk in the genesis of pathologic conditions and chronic diseases. Indeed, healthy skeletal muscle is the major energy consumer and contributor to maintain an elevated metabolic rate (MR) at rest (up to 30 % of VO2 max) and during exercise (up to 90 % of VO2 max) [1415] and prevents the genesis of disease. Because of this, an adequate muscle mass and function has to be set up as priority endpoint of recommendations for physical activity (PA) and dietary intake. Moreover, lifestyle behaviors have to be explored to optimize muscle health through the life span.

Exercise produces adaptations necessary to achieve recovery and resume homeostasis through muscle contractions [11]. Maintaining a healthy organ is associated with an intense exercise practice liable to develop muscle mass and its reservoir capacities [16]. A healthy muscle delays disability as we age and improves quality of life [1718]. Individuals die as a result of the end of the aging process and deterioration of muscle organ reserve that supports physical functioning [16].

A decreased muscle mass is an index for undernutrition, mortality, and physical disability [19]. In spite of its importance, other indexes such body mass index (BMI) and body weight (BW) are used to assess and predict health status, dependence, longevity, mortality, and risk of diseases [2021].

22.3 Research Findings

22.3.1 Bone and Muscular Growth in Active Female Through Lifespan

As Wolff postulated in 1892, bone in a healthy person will adapt to the loads it is placed under [22]. Muscular contractions represent the most important physiological stimulus that reinforce bone mass and resistance, setting up a possible connection not only between skeletal resistance and age [23] but also with muscular function [24]. This process begins during the fetal stage and increases during second and third decade of life; however, later childhood and adolescent years are the most sensitive periods with greater increases of 1–20 % in those who exercised before pubertal growth to 40–60 % occurring in those who exercised 2 years after menarche during adolescence and only a 5 % in those who exercised after the age of 18 [2527].

Bone mass (BM) variability depends on interindividual factors such as age, gender, heredity, pubertal development, and environment (e.g., age, gender). A BM accumulation is more related with pubertal growth, decelerating as adolescence progresses. Bone mineral density (BMD) continues in a linear positive path until twenties; nevertheless, in adulthood, bone grows naturally only when a fracture or an organic disease comes about. BMD losses range from 0.5 to 1 % per year starting in the mid-20s [28] and are more evident in women during the menopause period and subsequent years, where in 5 to 10 years, losses could stand between 5 and 8 % per year. After age 65, BMD losses slow reaching 0.7 % per year. Childhood and adolescence are the greatest times to gain enough bone stock to get greater bone mineral peak, gains that could be increased if exercise starts before adolescence. In addition, prospective studies in Britain and Swiss have reported that BM acquired during childhood determines BM in adulthood [2930].

Skeletal muscle mass (SMM) is the largest component of lean body mass in humans (40–50 % of total body weight), with more than 650 muscles allowing every movement and posture for human body [15]. At birth, the SMM is between 23 and 25 % of total body weight (BW) which continues growing by increasing the number of muscle cells (hyperplasia) for a short time after birth. Thereafter, SMM gains occur mainly by an increase in volume of muscle cells (hypertrophy) [31].

Much like BM, SMM changes depend on age, gender, ethnicity, and environmental influences. The SMM acquired in early life changes in early adulthood, where it is reported that fat weight increases while lean body weight (LBW) decreases. Losses result in a 10 % average between the mid-20s and 50s, which is probably caused by nutritional and physical activity changes. In a physically inactive population, after 30s, loss is approximately 3–5 % per decade, and a parallel decline in muscle strength occurs. In addition, after the 50s, greater losses occur varying acutely; thereby, individuals who maintain a good diet and perform resistance exercise programs lose on average an additional 30 % by the age of 80, while individuals unconcerned of their lifestyle (sedentary, poor nutrition, etc.) amass losses as much as 50 % of SMM gained during young adulthood. By the age of 80, half of the SMM has been lost [1532].

Sex differences that occur during and after adolescence show SMM accounts for 45 % of women’s BW compared to 54 % for males [31]. Those gender differences in total SMM result in a quantitative, not qualitative, muscular variance [33]. Such differences seem to be increased by a greater PA practice in males compared to females at any range of age [3436]. Those differences result in a poor muscle mass that make females more susceptible to injury, poor physical condition, lower bone mineral content, etc. In addition to the muscular variance, female QOL decreases sharply due to women living longer and having higher rates of disease [37].

Despite of losses in SMM taking place as a part of the aging process, in some cases they can be triggered by a muscle-related diseases (myopathies), inherited (dystrophies, congenital, inflammatory, metabolic, or endocrine myopathies) or acquired (toxic myopathies originated via food and drug administration), resulting in muscle weaknesses and physical impairment [13]. For that reason, the administration of treatments has to be taken in account in order to prescribe exercise to prevent a reduced function and muscle mass loss [3840].

Through the years research has focused more on the bone and joint consequences of the aging process than on muscle mass and functioning [41]. However, a decrease in SMM is an evident consequence of the aging process with a serious impairment of musculature functioning [134142]. The term sarcopenia was redefined recently by the European Working Group on Sarcopenia in Older People (EWGSOP) as an attempt to unify diagnostic criteria. Finally, sarcopenia was defined as the SMM loss associated with an impaired functioning affecting the physical performance [43], and according to this definition, both muscle mass (quantity) and functioning (quality) are affected [43]. Previous to a lack of consensus, epidemiologic research has reported values of sarcopenia from 8 to 40 % in elders between 60 and 70 years [44] and up to 50 % for those who are age 80 or above [4245]. Research has shown a higher incidence of sarcopenia depending on the gender, with greater values for females (8.5 %) compared to males (4.1 %) in 65–74 year olds [44]. Due to this methodological lack of concurrence, real values could have been underestimated for adults and elder population for years.

The primary factors affecting the degree of mass and function muscle loss are dietary protein intake and PA habits [4647]. In fact, subjects who show active lifestyle and healthy PA habits soften the muscle loss during the aging process [48].

There is a shift of muscle fiber distribution during the aging process that depends on two events: disuse (immobilization) and denervation. The lack of PA has shown a shift of muscle fiber distribution from slow to fast fiber type in aging subjects [4950], while denervation occurs mainly in fast motor units contributing to an increase of slower fiber type percentage content [4951]. Those adaptations are highly dependent upon PA and health rather than the aging process [52] and further affect the capacity to maintain posture and upright position against gravity (type I or slow fiber type) and the capacity to perform maximal strength and quick responses (type II or fast fiber type) [50].

During aging, the disproportionate unbalance between muscle protein synthesis and breakdown produces a loss in both fast and slow muscle fibers, showing a sharp loss of cross-sectional area of fast twitch type or type II fibers. Therefore, a motor unit loss occurs, and surviving motor units have to outface the loads which adapt through a net conversion of fast fibers to slow fibers. The loss of fast fibers is associated with a loss in muscle power necessary for quick movements (stand up, sit down, climbing stairs) and postural adjustments after stability perturbation. Moreover, this loss is accompanied by an increase of the placement of lipids in adipocytes and muscle fibers [52].

As muscle is lost, the bone turnover is affected because the mechanical stimulus to bone tissue and bone metabolism is decreased. Therefore, the rates of reabsorption and formation imbalance result in a bone mass loss and deterioration of bone microarchitecture [5354]. Research has reported a prevalence of 12.5 % sarcopenia in osteopenic premenopausal women. In addition, the 75 % of women suffering from osteopenia and osteoporosis presented associated sarcopenia, from which 25 % where osteopenic and 50 % osteoporotic postmenopausal women. Data suggest that the relationship of SMM, BMD, and risk of osteoporosis is largely associated to PA practice, showing lower incidence in regular PA practitioners [55]. The prevalence of osteopenia in the US population is 49 % in women beginning in their 50s (34 % men); moreover, osteoporosis prevalence is 18 % (5 % men) with higher percentages in female non-Hispanic white women (51 % osteopenia and 19 % osteoporosis) [5657]. Osteoporotic women have shown lower SMM compared with non-osteoporotic-matched controls [58] who show a positive relationship between LBM and BMD [5961]. Therefore, sarcopenic women presented lower LBM and BMD compared to non-sarcopenic postmenopausal women [57].

Bone-related diseases such as osteoporosis and osteopenia are not common in the young, healthy, and physically active population, such as children, adolescents, or young adults. Those conditions in the early stages of life are influenced by chronic-related diseases such eating disorders [62], cystic fibrosis [63], liver disease [64], renal disease [65], diabetes [66], or cancer [67].

22.3.2 Physical Activity Effects in the Muscular-Skeletal Tissue

Resistance training is so important that it is essential to maintain and strengthen other structures involved in physical performance. Not only do bone and muscle tissue receive benefits of physical activity, but other structures benefit as well. Normalized daily activity seems to be enough to maintain the 80–90 % of the mechanical properties of ligaments. Exercise causes the increase of the remaining 10–20 % of strength and stability in non-active female [6869]. Regular activity and exercise (including RT) help to maintain and/or increase strength levels and protect tendons from injuries [68].

In addition to muscular-skeletal effects, properly designed and supervised resistance training programs reported psychosocial benefits such as self-image, self-esteem, body image, social functioning, discipline, or collaborative capacity, showing greater improvements when participants start at a very low level if the stimulus is adequate.

22.3.2.1 Children and Adolescents

Physical activity (PA) benefits occur early in life. Recent studies have focused on the SMM benefits of children participating in sports, resistance training, plyometric training, and high-intensity training [7073]. Resistance and plyometric training both improve muscular strength and power; although, there are no obvious increases in muscle mass. Such muscular changes occur due to neurological adaptations in lieu of the lack of testosterone in children, a hormone known to promote muscle hypertrophy [70]. Muscles attach to growth plates in the bone, and the contraction of muscles in exercise and physical activity provides force application that stimulates proper bone growth [31]. BMD, bone mineral content, and growth hormone activity also increase with resistance and plyometric training and weight-bearing sports such as weightlifting and gymnastics [707374]. Research supports that PA during childhood and adolescence results in greater BMD than PA performed during adulthood, showing a 5–8 % higher bone density in those with healthy PA habits during their life [70]. Zanker et al. reported that high-impact exercise before 7 years old seems to be beneficial for BM acquisition. In prepubertal stages, some authors show gains from 2 to 4 % in BM related with different exercise programs; moreover, strength-related exercises and high-impact exercises such as jumps reported longer benefits [75]. Junior Olympic power lifters and gymnasts reported greater BMD values compared with the general population. In addition, preadolescents show higher BMD and strength after high-impact resistance training [18]. Interestingly, high-intensity training augments airway responsiveness and maximizes strength and power development [76].

Current evidence shows that preadolescent girls have similar strength to boys [77]. Sex differences on strength and other physiological adaptations are first observed during the adolescent stage of life. Adolescent boys become taller, more muscular, and have lesser body fat than girls [78]. However, girls go through adolescence earlier than boys [79]. This may suggest that physiological adaptations may be different between sexes during the late preadolescent stage and that exercise guidelines must be distinct for preadolescent girls. Unfortunately, studies on the physiological responses to exercise of young female athletes are scarce due to limitations of noninvasive experiments [78]. Thus, at present, exercise guidelines for preadolescent female and male athletes are the same.

22.3.2.2 Adult and Aging Woman

Research has reported that master athletes (those who train 4–5 days/week) show lower % BF than untrained subjects. In fact, master athletes’ data did not show significant differences in % BF and LBM compared with young athletes.

Interestingly, the master athletes who performed chronic exercise do not demonstrate the same losses of LBM and low-extremity strength compared to sedentary individuals. Wroblewski et al. used magnetic resonance imaging [53] to measure the subcutaneous adipose tissue [80], intramuscular adipose tissue (IMAT), and thigh total muscle area [81] in the low extremity. They included different MRIs comparing three subjects: a 40 year-old triathlete, a 74 year-old sedentary subject, and a 70 year-old triathlete that shows how mid-age adults and elder triathletes present similar TMA, SCAT, and IMAT. Actually, chronic exercisers presented higher functional capacity and QOL throughout the lifespan as age increased [52]. Also, according to Roubenoff [82], a resistance training program adapted to the population needs would lead to faster muscle contractions and greater force generation due to improvements in muscle fiber recruitment and firing rates [82].

It is known that protein synthesis rates decrease with age. However, research reported that progressive resistance training can increase protein synthesis rates in only 2 weeks. Those findings show protein synthesis rate increases up to 182 % following 2 weeks of a supervised RT program in 78–84 year olds [83], following 2 weeks of RT in 63–66 year olds [84], and increases by approximately 50 % after 3 month of supervised progressive RT in 76–92 year olds [85]. Such findings suggest that RT in older men and women increase the rate of muscle protein synthesis [86].

The ability to retain muscle mass and strength in the elderly has been demonstrated in those who practice chronic exercise [8788]; therefore, “chronic-exercise is prophylactic against age-related functional decline” [52]. Nevertheless, increases greater than 50 % in lower body strength can be obtained by performing short-term [89] and long-term [879091] training interventions in upper decades. Also, those interventions can maintain strength and muscle integrity across the life span [52].

22.3.3 How to Approach Strength Training with Children and Adolescents

Fortunately, most children do participate in adequate levels of physical activity. Adolescents, however, tend to show a decrease in physical activity even to the point where many do not even meet the recommended guidelines (American College of Sports Medicine, ACSM) [92]. Resistance training should be approached in a manner that will encourage a positive attitude toward physical activity, which might lessen the decrease in adolescents. Like most activities, it is important that children and adolescents should be having fun while participating. Resistance training is no different. For children (≤13 years old), most RT can be found on the playground. For children who are on the playground playing hopscotch or jumping rope or simply skipping, the National Strength and Conditioning Association (NSCA) states that these types of activities can be similar to plyometrics [70]. Playground equipment, such as jungle gyms, monkey bars, and rock walls, can encourage children to climb and pull themselves up [93]. These types of activities resemble load bearing and body weight RT.

Encouragement should also be an important part of establishing positive attitudes. Positive verbal encouragement can also help to make the activities more enjoyable [94]. The Centers for Disease Control and Prevention, or CDC, has made several recommendations on how to get and keep children active. They include but are not limited to, leading by example, going to parks or community recreational centers, encouraging them, and, again, making the activities fun [95].

22.3.4 Resistance Training Guidelines

The safety and efficiency of resistance training has been endorsed and recognized by the medical community and most major health-promoting organizations such the American Academy of Pediatrics, the American College of Sports MedicineBritish Association of Sport and Exercise ScienceCanadian Society for Exercise Physiology, and the National Strength and Conditioning Association.

22.3.4.1 Resistance Training Guidelines in Children and Adolescents

In the past, resistance training was avoided for children because of the fear that it would interfere with their growth. This fear was in reference to children’s growth plates closing prematurely with the stresses the resistance exercise placed on the plates. The theory originated from research on animal models and from monitoring the effects of the intense exercise regimen maintained by gymnasts, who seemed to have a corresponding decrease in growth [31]. Resistance training was also dismissed under the belief that children could not receive the benefit of increased strength due to their lack of androgenic hormones [31]. These schools of thought have faded though, with the understanding that RT can be done by children when the load applied is appropriate to the age and a qualified individual supervises the activity. In fact, it can be beneficial to children of all ages.

Even though there are several organizations and studies that have suggested their own guidelines for RT programs with children and adolescents, the guidelines are in agreement on several different aspects of the programs.

Supervision

Arguably the most important guideline might be that of supervision. The ACSM, NSCA, and AAP (American Academy of Pediatrics) all agree that a certified adult instructor should be with the youth at all times to ensure proper instruction and supervision [709296]. Also, studies done by Myer and Wall [97] and Miller and Cheatham [93] suggest in their guidelines that an instructor be present at all times to provide proper supervision and instruction. The AAP even suggests that an instructor to student ratio should be around 1:10 if the children are healthy [96]. Instructors should be able to teach proper lifting techniques (full range of motion for both eccentric and concentric contractions), breathing techniques, body position, and proper spotting techniques. Instructors can also help to maintain a clean and safe environment, as well as be able to adjust the program to meet the needs of those participating.

Recommended Age for Starting

The ACSM considers children to be <13 years old and considers adolescents to be between the ages of 13 and 18 [92]. They consider children and adolescents to be able to follow the same guidelines that apply to an adult population.

The NSCA has proposed several guidelines that are similar to those of the ACSM. Age ranges for the NSCA are 11–13 (children) with 12–18 and 14–18 for girls and boys, respectively (preadolescents and adolescents) [70]. Resistance training is not suggested for individuals under the age of 7 years old. This is because those individuals might not be mentally ready to participate in a structured program like RT.

The next set of guidelines is based on the Corbin pyramids. The author has developed physical activity pyramids that give guidelines for both kids and teens [94]. Corbin’s pyramids include a structured muscle fitness section designed for children under the age of 7. The types of exercises recommended for children include both body weight type activities and resistance band use [94].

Type of Exercise

The main resistance exercises need to be age- and ability-appropriate for the children, and the main focus when working with children is technique regardless of age or stage of development. The ACSM recommends both multi- and single-joint exercises [92]. These exercises should also include multiple muscle groups and major muscle groups, respectively, for multi- and single-joint exercises. This allows the child to perform the more difficult and tiring exercises without fatigue.

The NSCA recommends the use of simple exercises until proper form is maintained. Multi- and single-joint exercises incorporating both large and small muscle groups are encouraged as well. If a whole body workout is being performed multiple times a week, complex, multi-joint exercises should be done at the start [70]. Also, machine weight, free weights, body weight, and elastic bands are also supported [7092].

Warm-Up and Cooldown

The ACSM recommends that the resistance training session should include a 5–10 min warm-up period to get the body ready for physical activity, a stretching period, and a 5–10 min cooldown period. The stretching period can be after the warm-up or cooldown and should itself be around 10 min [92].

The NSCA also suggests a 5–10 min warm-up phase, and it should include dynamic movements. Current training recommendations include the utilization of dynamic warm-up [70]. Dynamic movements such as hops, skips, jumps, and movement-based exercises are better than performing static stretching to increase body temperature and motor unit excitability. The NSCA also recommends finishing the session with a cooldown phase consisting of calisthenics at a lower intensity [93]. Unlike the ACSM, the NSCA incorporates stretching into the cooldown period [7092].

Conditioning Phase Guidelines

According to the ACSM guidelines, the conditioning phase should be between 20 and 60 min long [92]. Resistance training guidelines recommended by the ACSM consist of 2–4 sets with 8–12 repetitions, or reps, per set, starting at roughly 60–80 % 1 RM. The sets can be composed of different lifts if desired. For example, one set of squats and one set of leg presses would equal two sets for the lower body. Also, keep in mind the inverse relationship between reps and intensity (as reps increase, intensity decreases). The recommended rest time should be between 2 and 3 min per set. When 8–15 reps can be performed with good form and moderate fatigue, progression is needed to ensure gains are continued. The guidelines suggest a frequency of 2–3 days/week and suggest that these days are not consecutive and should allow for 48 h between working on the same muscle groups whether they are part of a whole body workout or specific muscle group workout [92].

The resistance training phase guidelines for the NSCA recommend that the individual start at a low intensity, or a light load, of 1–2 sets consisting of 10–15 reps per set at roughly 50–70 % 1 RM [70]. Guidelines dealing with training for strength and power suggest 1–3 sets of 6–15 reps per set and 1–3 sets of 3–6 reps per set, respectively. Because power lifts use a higher velocity lift than those for strength, the resistance should be lower where it would be higher for strength. Strength exercises can have a higher resistance because the lifting velocity is slower at a more moderate pace. A shorter rest time of 1 min is suggested for most lifts; however, when the intensity is increased, the rest period should increase to 2–3 min. The frequency recommendations given by the NSCA are 2–3 days/week with those days being nonconsecutive in order to provide a 48–72 h break for recovery. A lower frequency can be used if the goal of the program is to maintain gains [70].

Corbin pyramid for teens or adolescents guidelines is set for 1–3 sets with 8–12 reps per set at roughly 40–60 % 1 RM [98].

Progression

Progression is discussed extensively in the updated position stand of the NSCA [70]; however, for this section, we will discuss it briefly. Progression is used to maximize gains and avoid staleness in the workout and should occur only after technique is mastered. During progression of resistance training, intensity should increase from novice to intermediate to advanced lifters. Because these guidelines are for children, most, if not all, of the individuals should be novices. If starting intensity was at 60 % 1 RM, progression could increase around 10 % for each of the other levels ending at 80 % 1 RM for advanced lifters. Volume is a little different. Again if the program begins at 1–2 sets at 10–15 reps, progression would see an increase in the number of sets but a slight decrease in the reps because we are still increasing intensity. Again as mentioned, rest time will increase with increasing intensity, and frequency can increase from 2–3 times/week up to 3–4 times/week. Power lifts follow a similar progression. While lifting velocity should stay relatively constant, after the first stage, more weight can be added to see greater power gains. Power progression should also see an increase in the number of sets with a slight decrease in the number of reps; rest times should increase; and frequency, which should start at 2 days/week, could increase to 3 days/week [70].

Corbin proposed that the progression for adolescents may be warranted when the individual can perform the maximum number of reps with moderate fatigue. At this point, reps should be decreased and weight should be increased. The frequency should be 3 days/week [98].

Long-term planning of a training program, called periodization, must also be done in order to avoid overtraining and boredom. Periodization refers to an organized and planned scheduling of varying training, performing exercises, and recovery. This includes planning resistance training sessions 2–3 times a week on nonconsecutive days for beginners and intermediates. Children who are advanced in RT may train 3–4 times per week.

As children age, the resistance exercises they engage in should also progress with them. Dr. William J. Kraemer suggest specific guidelines. Kraemer emphasizes that through each age division, the focus should lie in teaching exercise technique because that component of a resistance training program is of pivotal importance [99].

22.3.4.2 Resistance Training Guidelines with Adults and Aging women

Before getting into resistance training guidelines with adults and aging women, remember that resistance training is another form of exercise that allows the body to gain strength, power, and endurance; change one’s physique by increasing muscle size and losing excess adipose tissue; improve balance and proprioception; and enhance motor performance. This involves a wide variety of lifting exercises that require the use of body weight or external resistance such as free weights, weight machines, cords, and bands. Each exercise targets a specific muscle or muscle group. If performed correctly and consistently in a progressively effective manner, RT will inevitably change the muscle’s appearance and improve the capability of the body to perform movements.

Active adult women respond to resistance training similar to men with training adaptations leading to increases in hypertrophy, strength, power, and endurance. Muscle hypertrophy refers to the increase in muscle mass. Muscular strength refers to the ability of the muscle to generate force. Power refers to the strength of the muscle times the speed in which the action is performed. Powerful movements are explosive and dynamic such as jumping and throwing a ball. Muscular endurance refers to the ability of the muscle to repeatedly generate the same amount of force over a long period of time.

Resistance Training Guidelines for Adults

ACSM resistance training guidelines for adults are based in health-associated benefits of the muscular fitness established during the past decade. The following are general guidelines for the RT exercise prescription from the American College of Sports Medicine [1]. Appropriately designed RT improves the different components of strength (power, function, and endurance) which result in an improved muscular fitness [8].

Types of Exercise/Exercise Selection

Exercises can be performed using multiple modalities such as free weights, machines, cords, and unstable equipment. Both free weights and machines are effective for increasing strength; however, weight machines are recommended for novice to intermediate exercisers because they are safer and easier to use where emphasis in free weight exercises is recommended for advanced resistance training [8].

In adults, resistance training exercises include both single- and multi-joint exercises and unilateral and bilateral exercises. Single-joint exercises are useful to engage specific muscles while multi-joint exercises are capable of involving major muscle groups which require greater coordination and muscular balance. Multi-joint exercises have been reported as more effective to promote strength gains because more weight can be lifted [100]. Both unilateral and bilateral exercises produce gains in strength, and further unilateral exercises are useful in sports performance abilities [8].

It is recommended that novice, intermediate, and advanced individuals perform dynamic repetitions with concentric (CON: muscle shortening) and eccentric (ECC: muscle lengthening) muscle actions as well as isometric contractions (ISOM: no changes in muscle length) to stabilize core strength and specific isometric exercises [8].

Additionally, functional exercises are recommended to enhance muscular balance in joints, the core, pelvic, and scapula girdles [101].

Warm-Up and Cooldown

There is an increasing importance of the dynamic warm-up due to the ability to increase body temperature, motor unit recruitment, kinesthesis activation, and joint mobility [81101103].

Conditioning Phase Guidelines

As mentioned before by Roubenoff [82], optimum volume allows functional and structural adaptations according to the objectives. Therefore, training out of the optimal stimulus will promote the risk of injuries or will not produce the expected results. The ACSM insures that altering the number of exercises, number of repetitions, and sets, or load, alters the training volume [8]. Due to the interindividual differences in the adaptation response to resistance training, minimum, medium, and maximal volumes are used to program exercise [9]. There is a recommended minimum volume of 1–3 sets per exercise (each muscle group) in novice individuals initially for the first 4 weeks of RT [8104105]. For intermediate and advanced individuals, research has reported that multiple-set programs with a systematic variation related to the program priorities are recommended [8]. For a medium volume, a recommendation of 4–9 sets (each muscle group) should be used depending on the individual’s level (4 sets for a lower intermediate level and 6–9 for a higher intermediate level) and type of exercise selected (4–6 sets for major muscle groups and 8–9 sets for small muscle groups). Maximum volume is aimed at an advanced level, varies between 9 and 12 sets (each muscle group), and is recommended for a high-level, physically conditioned individuals with an RT background [9].

Resistance training frequency recommendations in novice individuals are lower at 2–3 days/week and focus on the entire body. The progression from a novice to an intermediate level depends upon other variables such volume and intensity more than frequency. Therefore, it is recommended that an intermediate individual progresses to 3–4 training days (e.g., from total body workout using 3 days to split body routines using 4 days). Frequency to progress toward an advanced training may vary depending on the objectives, recovery needed, nutrition supplementation, and sport specialization. Football players obtain better results if they train 4–5 days/week, while weight lifters and bodybuilders use high-frequency training programs double splitting routines at 8–12 training sessions per week.

Evidence loading statements and recommendations to maximize muscular strength are loads of 60–70 % of 1 RM for novice to intermediate and 80–100 % of 1 RM for advanced individuals. Notwithstanding, depending on the type of strength that is aimed to improve, the conditioning guidelines are different. The ACSM position stand presents three program designs: hypertrophy, muscular power, or muscular endurance. Therefore, loading, volume, exercise selection, exercise order, and resting periods are adjusted to obtain specific results [8]. These current resistance training guidelines include recommendations for increasing muscle hypertrophy, strength, power, and local muscular endurance. And these recommendations are dependent on physical capacity and training status.

Many different exercises are available for each target muscle or muscle group. In order to efficiently increase muscle hypertrophy, it is recommended that the resistance training program includes a combination of exercises that involve concentric, eccentric, and isometric muscle actions and use single- and multi-joint movements. Typically, a baseline program for novice and intermediate training may include four upper body, four lower body, and two core/abdominal exercises. For advanced training (>3 days/week), it is recommended that a split routine be used (e.g., first and third day: upper body; second and fourth day: lower body). The recommendation for sequencing during an RT session is to first perform exercises that utilize larger prior to small muscle groups, multi-joint prior to single-joint exercises, or higher intensity prior to lower intensity exercises. Next, interchange between upper and lower body exercises, or exercises that utilize opposing muscle groups. A key element is using the appropriate weight for the desired number of repetitions. To increase muscle hypertrophy among novices and those with some experience (intermediate), performing resistance exercises with moderate weight is recommended (70–85 % of 1 RM) for 1–3 sets of 8–12 repetitions per exercise. Novices in RT should also focus on learning the proper technique for performing the exercises prior to using heavy external resistance. Those advanced in RT (> 1 year of experience) may opt for a more varied program where the loading range is from 70 to 100 % of 1 RM for 3–6 sets of 1–12 repetitions per exercise; however, more repetitions (6–12 RM) are recommended. RM (repetition maximum) refers to the maximum number of repetitions one can perform with a particular weight or external resistance. The magnitude of change in hypertrophy decreases as the muscle becomes accustomed to the load of the external resistance. Therefore, progressing to a heavier external resistance is necessary to avoid training plateaus. The recommendation is to increase the load by 2–10 % when one can perform the exercise with additional 1 or 2 repetitions over the prescribed number of repetitions. Another way to progressively overload the stress placed on the skeletal muscle is through increasing the total repetitions (training volume) performed at the current load. Limiting the rest interval to 1–2 min per set of moderate loading (for novice and intermediate) and 2–3 min per set of heavy loading (for advanced) is recommended. Training frequencies of 2–3 days/week for novices, 2–4 days/week for intermediate, and 4–6 days/week for advanced are recommended. The rest days are for recovery and are essential to prevent the negative effects of overtraining.

The recommendations for increasing muscular strength are similar to that of increasing muscle hypertrophy with the exception of training load, intensity, volume, and rest interval for intermediate and advanced individuals. Novices and intermediate level individuals are recommended to perform resistance training exercises with a load between 60 and 70 % of 1 RM for 1–3 sets of 8–12 repetitions with eventual progression in training load. Intermediate and advanced individuals are recommended to train using systematically varied and progressive multiple-set programs at loads between 80 and 100 % of 1 RM with emphasis on heavy loading and less repetitions (1–6 RM). For heavy loads, the recommended rest interval is longer (3–5 min per set) to allow the body to fully recover prior to performing another set. This has been shown to promote greater strength increases.

To increase muscular power, it is recommended that multi-joint exercises be predominantly used and performed through systematically varied loading strategies. Performing exercises with heavy loads (85–100 % 1 RM) in combination with explosive exercises using light to moderate loading (30–60 % of 1 RM for upper body exercises and 0–60 % of 1 RM for lower body exercises) for 1–3 sets of 3–6 repetitions is recommended. The recommended exercise sequence is similar to the recommendations in increasing muscular hypertrophy and strength. Furthermore, it is recommended that a resistance training program be integrated with the power program. The recommended rest interval is 2–3 min per set for high-intensity exercises and 1–2 min for low-intensity exercises. This resistance training program also follows similar guidelines dealing with progression toward heavier loads. Training 2–3 days/week for novices, 3–4 days/week for intermediate, and 4–5 days/week for advanced is recommended. When training greater than 3 days/week, a split routine is recommended.

Resistance training for increasing muscular endurance involves performing more repetitions of the exercises using lighter loads. The program must also progressively increase in load and volume. It is recommended that single- and multi-joint exercises be performed with a light load for multiple sets of 10–15 repetitions for novice and intermediate training and ≥25 repetitions for advanced training. A short rest interval between sets (1–2 min after performing ≥15 repetitions and <1 min after performing 10–15 repetitions) is recommended (for a summary of RT program design, see Table 22.1).

Table 22.1

Variables manipulation depending on the aim of the resistance training program design

Hypertrophy

Power

Endurance

Loading and volume

Novice and intermediate:

Moderate loading (70–85 % of 1 RM)

8–12 reps per set

1–3 sets per exercise

Advanced:

Loading range 70–100 % of 1 RM

1–12 reps per set

3–6 sets per exercise

Light to moderate loading: 30–60 % of 1 RM for upper body and 0–60 % of 1 RM lower body

1–3 sets per exercise

Progression ranges from heavy loading: 85–100 % of 1 RM to increase the force component, or 30–60 % of 1 RM for upper body and 0–60 % of 1 RM for lower body to increase fast force production

Multiple (3–6) sets per exercise

1–6 reps

Novice and intermediate: light loads with large reps (10–15) increase local muscular endurance

Advanced: various loading strategies for multiple sets per exercise (10–25 reps per exercise)

High volume

Frequency

Novice: 2–3 days/week

Intermediate: 4 days/week for total body and split routine

Advanced: 4–6 days/week for split routines

Novice: 2–3 days/week stressing the total body

Intermediate: 3–4 days/week for total body and split routines

Advanced: 4–5 days/week for predominantly total body routines

Novice: 2–3 days/week stressing the total body

Intermediate: 3 days/week for total body workouts and 4 days/week for upper/lower body split routine workouts

Advanced: 4–6 days/week if split routines are used

Exercise selection, order, and velocity

Single- and multi-joint exercises

Free weight and machine exercises

Novice and intermediate: slow to moderate velocities

Advanced: slow, moderate, and fast depending on the load, repetition number, and goals of each

Fast lifting velocities are needed to optimize power development with submaximal loading

Unilateral and bilateral exercises

Single- and multi-joint exercises

Slow velocity when 10–15 (moderate number) reps

Moderate-fast for increasing repetition number. Faster for large number of reps (15–25 or more)

Rest periods

Novice and intermediate: 1–2 min

Advanced (corresponding to each exercise goals or training phase): 2–3 min for high loading for core exercises, or 1–2 min for moderate to moderately high loading of other exercises

At least 2–3 min between sets for core exercises, or 1–2 for assistance exercises

Short rest periods, for example,

1–2 min for high-repetition sets (15–20)

<1 min for moderate-repetition sets (10–15)

For circuit, weight training recommends resting periods that take place from going to one station to another

Progression

Progression for adults depends on increasing the resistance to promote additional gains. To obtain such gains, the program variables (frequency, intensity, volume, rest intervals, exercises, etc.) have to be suitable to individual characteristics and goals [8].

For progression in those individuals training at a specific load, there is a recommended 2–10 % increase when individual exceeds the current workload on two consecutive sessions [8]. For novice individuals, progression is recommended at 1–3 sets per exercise, and for intermediate to advanced, progression occurs through multiple sets with a systematic variation of volume and intensity, but not all exercises need the same number of sets. That is dependent on the goals and muscle group trained, for example, lifting more upper body than lower body.

To reduce the risk of overtraining and injury, it is not recommended to increase drastically. Besides, not all the exercises need the same number of sets, intensity, or repetitions [8]. Inappropriate manipulation can limit the magnitude of improvements and decrease the level of muscular fitness. To avoid these issues, variables should be manipulated based on the progression principles: progressive overload, specificity, and variation [106]. Progressive overload or gradual increase of stress is recommended by altering one or more of the following variables: intensity (absolute or relative), total repetitions at the current intensity, repetition speed, resting periods, or volume [107]. Specificity, “all training adaptations are specific to stimulus applied” determined by the muscle actions, speed of the movement, range of motion, muscle groups trained, intensity, and loading [8]. Therefore, successful resistance training programs are designed for specific purposes (e.g., hypertrophy, muscular speed/power, or muscular endurance). Variation and periodization are systematic processes applied to manipulate the training variables. The most studied have been intensity and volume [108109]. However, periodization can be organized in linear (classical and reverse periodization) and nonlinear models (undulating periodization) affecting the way intensity and volume are manipulated. For instance, classical periodization applies high volume and low intensity at the beginning of the training program while reverse periodization initiates applying high intensity and low volumes, and at the undulating periodization, intensity and volume variations alternate.

Elder Resistance Training Guidelines

The development of sarcopenia and osteoporosis is multifaceted, and many of the causative factors are uncontrollable. Resistance training has been shown to be a powerful intervention in the prevention and treatment of sarcopenia [33], as well as positively influences the neuromuscular system, hormone concentrations, and protein synthesis rates. Muscle protein synthesis increases after one bout of high-intensity training and peaks approximately 24 after exercise. Moreover, the anabolic effect of the RT is maintained 36–48 h before losses start [8]. For that reason, frequency recommendations should be regulated depending on the population characteristics (initial PA, body composition status, nutrition, disability level, disease, etc.) owing to the value of the SMM as an essential index for independence, longevity, absence of disease, and QOL. The American College of Sports Medicine published in 2009 the “Exercise and Physical Activity Guidelines for Older Adults” [110] which suggests a frequency for RT at 2 days/week.

The ACSM basic recommendations for muscular strength in adults have proven to be effective guidelines for the elderly. However, to progress toward higher levels, it is important to introduce changes gradually. The muscular power ability decreases with aging, and improvements in this type of strength can reduce the risk of falls and enhance the capacity to perform daily tasks.

Supervision and Safety Points

The role of the instructor supervising and monitoring the training for elders is essential because many individuals must be educated and directed properly. Teaching correct lifting techniques has to be a priority with this population [111].

Eccentric training results in greater muscle soreness; therefore, caution is recommended in programs that include this type of muscular action [112]. In addition, excessive resistance training loads may acerbate a preexisting condition [111].

Aging adults have to perform exercises “pain-free” with controlled joint movements. This means that individuals with arthritis and joint and bone disorders have to avoid training during times of pain and inflammation. Further, the breathing patterns during resistance training exercises have to be taught to prevent apnea during the practice.

Resistance training can be progressively introduced to individuals with cardiovascular, metabolic, pulmonary, renal, psychiatric-related, and other diseases. Moreover, individuals with uncontrolled conditions (e.g., hypertension, chest pain, metabolic disturbances) need medical assessment prior to training [111].

Type of Exercise

For improvements in strength fitness, free weight and machine exercises are recommended. Older adults must perform multiple- and single-joint exercises with a slow to moderate lifting velocity [8110].

However, most of the time, free weights and machines are located at gyms or other facilities which some elderly individuals do not have access to on a regular basis. Resistance training can be accomplished, despite not having access to a facility, with the use of therapy bands, fit-balls, and other equipment as well as self-body weight.

Conditioning Phase

The ACSM recommends starting resistance training with elders using minimal resistance loads for 8 weeks to allow the joints and connective tissues (e.g., ligaments, tendons) to adjust. After a period of not training, it is recommended to restart the training with loads 50 % or less than previous intensity [92]. For muscular strength, 1–3 sets with loads from 60 to 80 % of 1 RM are recommended. The rest periods are 1–3 min if volume is 2–3 days/week. When the objective is to increase muscular power in healthy older adults in addition to muscular strength, it is recommended to perform 1–3 sets per exercise using light to moderate intensity (30–60 % of 1 RM) and 6–10 repetitions with high velocity. Moreover, recommendations to improve local muscular endurance are similar to young adults where moderate to high repetitions (10–15 reps) are used with low to moderate loads (40-–70 % of 1 RM) [8].

Furthermore, to enhance better stability, muscle proprioception, and coordination, functional exercise in a standing position is recommended [111].

Progression

The progression guidelines are reported by the ACSM in the “Progression models in resistance training for healthy adults” [8]. Some authors suggest overload first by an increase in repetitions, followed by an increase in resistance [92]. Therefore, the manipulation of the variables will depend on the adaptations of the individual, as well as the health status, strength level, and goals.

22.3.5 Resistance Training as a Preventive Factor from Injuries and Healthy Posture in the Future

Resistance training has been found to be an effective form of injury prevention. The NSCA made note that training should be effective in reducing acute and overuse injuries related to sports [70]. In female athletes, training combined with proper form instruction has been shown to decrease ACL injuries. However, one area of concern is that a lot of RT programs are being implemented during a preseason workout. Coaches and instructors have to be careful because adding to workout time could lead to overuse injuries. Therefore, proper rest periods have to be implemented as well [70].

Faigenbaum and Schram looked at five studies dealing with resistance training and incidences of sport injury [113]. The subjects of the articles they reviewed were divided into an exercise group and a control group, ranged in age from 13 to 19 years old or were listed as high school students, and included both males and females. The subjects were also involved in a variety of sports from handball to football. The training time lasted anywhere from 5 to 6 weeks up to 1 year. The training offered was a multicomponent program that included RT with other forms of training such as cardiovascular, flexibility, and speed and agility drills. Resistance training included weight training, plyometrics, and proprioceptive training. No study made use of all forms of training. One study looked at only training in the form of proprioceptive and plyometric training. All studies reported a decrease in injuries, ranging from knee to acute and overuse injuries, as compared to the control group [113]. Another study by Faigenbaum and Myer agreed that a comprehensive program could help in injury prevention in young athletes [114].

Posture is another area in which resistance training can be beneficial. Corbin et al. list two problems concerning the muscles that can contribute to problems with posture: muscle inflexibility and muscle weakness [98]. When muscles on either side of a joint are weaker or more inflexible than the ones across the joint, poor posture will follow. Stretching, which should also be a part of physical activity, should remedy muscle inflexibility. Exercises that work on strengthening the core muscles are recommended for development of a healthy posture [96]. A proper RT program will strengthen the muscles and allow for a proper posture to be developed.

22.4 Contemporary Understanding of the Issues

Resistance training can improve health no matter which stage of life the individual is in. Bone health can be improved when an increased load, which is achieved through RT, is placed on the bone [2123]. Most of these gains have been seen in late childhood and adolescence [2426]. It is important to see these gains, because of bone mineral density (BMD). After the 20s, BMD drops as individuals age and a healthy gain in BMD during the earlier years of life can lead to a larger amount in adulthood, which could slow the onset of several bone-related diseases [2729].

Skeletal muscle mass (SMM) also experiences great benefits when a resistance training program is established. Even though initially gained through hyperplasia, SMM traditionally increases through the process of hypertrophy, which is brought on by RT [30]. Much like bone loss, SMM loss, which starts in the mid-20s, can be hindered by a proper RT program. Also, RT can help build a larger volume of SMM by the time the loss begins [1431].

SMM is also affected by gender differences with females showing a lower percentage of SMM as a part of overall body weight [30]. These changes are thought to be brought on by adolescence and the fact that more males than females tend to participate in physical activity [3335]. This lack of physical activity can carry throughout the lifespan and lead to muscle fiber type and motor unit changes, which can be issues when trying to carry out general tasks [4851].

Both the losses in bone and skeletal muscle mass can be intertwined. Remember that bone can be strengthened by a muscle applying force to an area of that bone [2123]. If individuals show a loss of SMM through a lack of physical activity (such as resistance training), bone loss and diseases can occur due to a lack of stimulus to the bone. This would also affect bone formation and breakdown [5253]. If the force is no longer applied to the bone, the bone is not being strengthened where it would be if the force was being applied. At this point diseases such as osteopenia and osteoporosis can occur. In fact, research has shown that sarcopenia (loss of SMM) tends to accompany osteopenia and osteoporosis in women, who tend to participate in physical activity less than men of the same age group [54].

Trying to establish good physical activity habits early in life is paramount because there are a host of benefits in participating in physical activity. Resistance training in children and adolescents can produce increases in BMD and increases in strength and power [6973]. For relevance toward females, most females show similar strength levels when compared to their male counterparts before adolescence starts [76]. After adolescence, males tend to surpass females in terms of height, strength, and lean body mass [77]. Despite this difference, guidelines for physical activity, including RT, are mostly the same for both genders.

Previously, resistance training of any kind was considered to be detrimental to children and adolescents [70113114]. The main area of concern involved the epiphyseal cartilage, more commonly known as the growth plates. These tissues were considered to be weak compared to the surrounding structures and therefore more easily injured [70]. Even though injury to children and adolescents is still a concern to many [93], currently, RT has been shown to be safe and effective when proper instruction and supervision is available [709697113114]. Remember that when approaching children and adolescents with an RT program, make sure it is fun [95]. Also, encouragement is also an integral part in getting the individuals to continue participating in the program [115]. Encouragement can come from teachers or parents and should get the kids moving and trying new activities.

The guidelines for resistance training in children and adolescents have come from several sources. Supervision by a qualified instructor is of the upmost importance [7092939697]. Instructors can teach proper technique and insure a clean workout area to maximize safety. Children should participate in some form of the RT that overloads their muscles at a frequency of 60 min per day at 2–3 days/week [94].

For individuals that are both mentally and physically ready to participate in a structured training program (usually around 7–8 years old) [709396], different guidelines are suggested. Exercises should include both multi- and single-joint lifts which work both large and small muscle groups. A 5–10 min warm-up and cooldown phase should be included in the training session and include stretching. The intensity should be 1–4 sets consisting of 8–15 reps between 40 and 80 % 1 RM depending on skill level with at least 1–3 min rest between sets [709298]. During the resistance training phase, novice individuals should start with a lighter load until proper form and technique can be maintained [70]. Progression should only happen when the lifts can be performed with moderate effort while maintaining proper form and technique [70]. Also, keep in mind that if there is an increase in weight, the number of either sets or reps should drop and rest might have to be increased [98]. The frequency should be 2–3 nonconsecutive days per week [7092] and should last around 60 min per training session (for a summary of guidelines, see Table 22.2) [98].

Table 22.2

Summary of resistance training guidelines for children and adolescents

1. Make sure a certified instructor is present to ensure proper form or lifting technique is used and a safe environment is maintained

2. For young children, resistance should be from body weight and resistance bands, look to overload the muscles, and should last for 60 min/day at 2–3 days/week

3. For older children who are ready to start a resistance training program (starting at 7–8 years old) and adolescents, machine weights, free weights, body weights, and resistance bands are acceptable

4. Exercises should include multi- and single-joint lifts, working both large and small muscle groups

5. A 5–10 min warm-up and cooldown should be part of the training session and involve stretching

6. Resistance training should include 1–4 sets, 8–15 reps/set

7. Resistance should be set at ~40–80 % 1 RM, with beginners starting with a lighter load

8. Progression should be used when needed. Progression should occur when lifts can be made with proper form and technique at a moderate effort

9. Resistance training should occur 2–3days/week that is nonconsecutive and the session should last 60 min

Source: Adapted from American College of Sports Medicine. ACSM’s guidelines for exercise testing and prescription. 8th ed., Baltimore: Lippincott Williams & Wilkins, 2010; Faigenbaum, AD, Kraemer, WJ, Blimkie, CJR, et al. Youth resistance training: updated position statement paper from the national strength and conditioning association. Journal of Strength and Conditioning Research. 2009;23(Aug):S60–S79; Corbin, CB, Le Masurier, GC, Lambdin, DD, et al. Fitness for life: elementary school guide for wellness coordinators. Champaign: Human Kinetics, 2010; and Corbin, C, Welk, G, Corbin, W, et al. Concepts of physical fitness: active lifestyles for wellness. 16th ed., New York: McGraw-Hill, 2011

For the adult and aging woman, physical activity can have positive effects. In those who train at least 4–5 days/week, lean body mass and body fat percentage are similar to those who are younger. When comparing the measure of a 40-year-old and 70-year-old, both triathletes, to a sedentary 70-year-old, the triathletes produced similar intramuscular adipose tissue and total muscle area in the thigh, as well as higher functional capacity and quality of life [51]. Also, adult and aging women show increases in protein synthesis after implementing resistance training [8183]. Elderly individuals have also shown increases in strength after bouts of short- and long-term training [858789].

Adult women, who participate in resistance training, show similar changes in physique, balance, and performance as their male counterparts when the training is correctly executed and consistent. These changes also include those to hypertrophy, strength, power, and endurance. Regardless of gender, hypertrophy, strength, power, and endurance, each has its own set of guidelines, such as those set by the ACSM, to maximize gains for that specific type. Also, in the case of experience, whether the lifter be a novice, intermediate, or advanced exerciser, different guidelines must be followed to ensure safety and efficiency.

All levels of lifters should perform single- and multi-joint exercises that are unilateral and bilateral, as well as both concentric and eccentric contractions of dynamic repetitions, and isometric exercises [7]. This can also be the period where functional exercises start to work their way into the program [99]. Dynamic warm-up is also needed to prepare the body for the work that is about to be done [99102].

For the actual resistance training program, it is recommended for novices to build up by performing 4 weeks of 1–3 sets per exercise with a lower volume. After the initial 4 weeks, the number of sets can also increase to 4 and then to 9 during the intermediate level, with major and small muscle groups having 4–6 sets and 8–9 sets, respectively [7]. Once an advanced level is obtained, a set range of 9–12 sets can be implemented [8].

When dealing with frequency of resistance training, it must be noted that rest is key for the muscles to heal and repair between work days. Frequency can be determined by several variables, and depending on these variables, RT can be done with a frequency from a few sessions/week up to 12 sessions/week. Novice and intermediate RT programs should have a frequency of 2–3 times/week and 3–4 times/week, respectively. Advanced individuals can have upwards of 12 lifting sessions/week depending on what is needed to be accomplished [7].

For novice and intermediate lifters, a load of 60–70 % of the 1 RM is recommended, while advanced lifters are recommended to lift 80–100 % of their 1 RM [7].

All of these guidelines can be manipulated to perform a specific function or lead to a specific type of gain for the individual participating in the resistance training program. Lifting different variations of the guidelines can lead to gains in hypertrophy, strength, power, or endurance.

Generally, gains in hypertrophy require both single- and multi-joint types of movements, and the lifter must use concentric, eccentric, and isometric contractions. Novices and intermediates should lift 70–85 % of their 1 RM, at 8–12 reps/set for 1–3 sets, with advanced individuals lifting upwards of 70–100 % of their 1 RM at 1–12 reps/set for 3–6 sets. These workouts can be done at a frequency of 2–3 days/week for novice individuals, 4 days/week for intermediates, and 4–6 days/week for advanced individuals. Novice individuals should lift whole body routines (composed of both upper and lower body as well as core exercises), while advanced individuals should lift split routines (alternating between upper and lower body). Intermediates can lift either. Rest should be between 1 and 2 min from one set to another for novice and intermediate individuals and 1–2 min for moderate loads and 2–3 min for high loading or core exercise for advanced individuals [7].

When putting together a resistance training program geared toward strength, the values are similar to that of hypertrophy. Novice and intermediate individuals should drop to 60–70 % 1 RM at 1–3 sets with 8–12 reps/set. Depending on the level of an intermediate lifter, they can be considered part of the advanced group and lift 80–100 % of 1 RM with fewer sets and reps/set. Strength training will also benefit using 3–5 min rest periods as opposed to the shorter rest periods used for hypertrophy [7].

Muscle power is based on the rate (speed) of force production. So it only makes sense that muscle power is going to be achieved by performing fast lifts in the resistance training program. Heavier loads are still going to be used to increase the amount of force produced. So heavy loads of 80–100 % 1 RM are going to be integrated with lighter loads of 30–60 % for upper body and 0–60 % for lower body for 3–6 reps/set for 1–3 sets. This RT program will have a frequency of 2–3 days/week, 3–4 days/week, and 4–5 days/week for novice, intermediate, and advanced lifters, respectively. Also, intermediate and advanced lifters can use split routines. Resting periods should be 1–2 min for low intensity and 2–3 min for high intensity [7].

The key to muscle endurance is high volume at low intensity. This helps to prepare the muscles to last for longer periods of time. Novice and intermediate lifters should lift a light load for 10–15 reps while advanced individuals should lift 10–25 reps. Frequency for novice, intermediate, and advanced lifters is 2–3 days/week, 3–4 days/week, and 4–6 days/week, respectively. Also take note that split routines should be used when the frequency is 4 days/week or greater. A shorter rest period of less than 1 min should be used when 10–15 repetitions are completed, and when repetitions are greater than 15, 1–2 min of rest should be used [7].

Progression should occur when the individual is able to perform more than their current workload on two consecutive sessions [7]. If progression does not occur, the individual will hit a plateau where no further gains will be attained. Progression can occur through progressive overload, specificity, and variation [105]. Changing intensity, number or speed of reps, volume, or resting period are all considered to be progressive overloading [106]. Specificity changes could involve changes to muscle actions, ranges of motion, or even switching from one program to another [7]. Variation, also known as periodization, is altering variables such as intensity and volume. Switching between a high volume and low intensity to a low volume high intensity can lead to changes.

Even though many consider the elderly too weak to resistance train, there are several benefits that can be experienced. Two problems that tend to affect the elderly involve bone disorders, such as osteoporosis and osteopenia, and sarcopenia. Resistance training has been shown to help with sarcopenia [32]. This effect can, in turn, help with bone loss. Remember, women who showed lower levels of SMM also presented lower levels of LBM and BMD, with less incident in all for those who participated in physical activity [5460].

The ACSM has set a standard of guidelines for the elderly, so they too can participate in resistance training. Safety must be a priority with the elderly, and only through proper technique can safety be insured [110]. Also, if any individual has preexisting conditions, a medical assessment should be considered because RT can acerbate those conditions [110].

While single- and multi-joint exercises using free weights, machines, and a multitude of other types of resistance are approved [7109], eccentric contractions need to be avoided because they can cause pain [111]. Standing exercises should be considered because of their health benefits [110]. Minimal resistance loads are recommended for the first 8 weeks, and only 50 % of previous workload should be used if the individual took a long break [91]. This helps with minimizing pain caused by lifting which could cause them to abandon any type of resistance training program.

The guidelines themselves are very basic, but they are the same as those for adults. The main objective for the elderly is to be able to get to the point where they can perform activities of daily living. While strength, power, and endurance are a concern for them as well as a younger population, the younger population obviously wants those changes for a different reason.

Muscular strength guidelines are 1–3 sets at 60–80 % 1 RM, with a 1–3 min rest period. These guidelines are also incorporated into the guidelines for power, which are 1–3 sets at 30–60 % 1 RM and 6–10 reps at a higher velocity. Finally, endurance training has a higher rep number of 10–15 reps but at a lower intensity of 40–70 % 1 RM [7]. For all resistance training, a frequency of 2 sessions/week is recommended [109]. This allows for plenty of time for recovery. Progression will follow the adult guidelines.

When performed properly, RT can help to reduce the occurrence of injury [113114] and improve posture [9698]. Resistance training has been shown to decrease the number of knee injuries and the number of acute and overuse injuries in young athletes. When added to a preseason program, it can also prepare the athlete for participation, which could decrease injuries as well [70113]. Posture can be helped by training the core muscles [96]. Training will help strengthen the muscles that are weaker than the surrounding muscles which will help in improving posture [98].

22.5 Future Directions

Continuing research in physical activity is paramount in understanding how the body works and developing a means to maximize results. By understanding one aspect of the muscle, theories could be developed and tested in maximizing energy use, causing gains in hypertrophy, strength, power, and endurance, and maximizing healing times. If research could reveal the specifics of strength development, resistance training programs could be developed that would maximize gains in a minimal amount of time.

One future direction for resistance training could be to look at how one might approach RT toward children. Again with the age of 7–8 years old ideal for a structured RT program, one could look at possibly implementing a program before that age. Designing programs with a semi-structured layout (one that involves both structured exercise and free time) might be an effective way to get younger children used to a structured program that could then be developed more as they get older.

The guidelines are what drives and ensures the safety of a proper resistance training program. While many organizations and individuals agree on several aspects in the guidelines, there are some differences. The ACSM and NSCA both have different recommendations for sets and reps. The NSCA also included guidelines for power type RT. Future studies could provide some clarity on exactly how many sets and reps are needed to best fit the athlete. Also, if guidelines are available for strength and power, could there be other guidelines specific to muscular endurance?

Another direction could lead to changes in physical activity in children and adolescents. Currently, preadolescent female athletes have no guidelines of their own, despite the differences in male and female athletes. Because females experience an earlier onset of adolescent changes, it might be beneficial to develop different resistance training guidelines to adjust for those changes in the late preadolescent period.

For adults, future directions in physical activity could look at implementing functional exercises into a resistance training program. As we age, activities of daily living can become difficult to carry out. Functional exercises could make it easier to perform these tasks. By developing and implementing a proper functional exercise program to go along with RT, one might be able to delay or even possibly eliminate problems dealing with everyday functioning.

For the elderly, there are a couple of directions physical activity could be taken. One major aspect of the elderly is the threat of diseases to physical activity. While the exercises need to be performed “pain-free,” many elderly individuals are not able to perform some activities without experiencing some level of pain. The development of guidelines could help minimize the pain experienced. Also, gains tend to be lost quicker in the elderly population. The development of guidelines to help maintain gains, even when not in a program, could serve the elderly population greatly.

One aspect of the studies dealing with overall effects of resistance training on injury prevention was the use of a multiple component training program. Most studies combined RT with some other form of training or instruction. Future studies might look at how much of a part RT alone would play in decreasing the number of injuries. Another possible direction for future studies could look at using RT as a preventative method when added to a preseason program. Also, when dealing with posture, one could look at muscular strength vs. muscular flexibility. Again this could show if RT had more of an effect on posture or flexibility training.

22.6 Concluding Remarks

Recent research in resistance training has shown how beneficial it can be in all stages of life for overall physical health, especially in relation to bone and skeletal muscle disorders. This is especially important for females because of their higher incidences of osteoporosis and osteopenia, as well as sarcopenia. An RT program can help improve skeletal muscle mass, which, in turn, can help improve bone health. These gains can also help in slowing down further losses that are associated with the aging process.

In order to receive maximum gains from resistance training, specific guidelines had to be put into effect that would benefit individuals across the entire lifespan. Guidelines were developed that include children and adolescents, adult women, and the aging woman. While these guidelines generally cover both men and women, women can see the same benefits as their male counterparts. Children and adolescents have guidelines that are focused on developing a healthy attitude toward physical activity and making sure they are properly supervised and mentally and physically ready and have a proper RT program that allows them to achieve the increases in strength they are able to attain. Some of the greatest gains in bone health and skeletal muscle mass occur during this time period. Adults and aging women also have their own RT guidelines. Adults have guidelines that allow them to increase hypertrophy, power, and muscular strength and endurance. Guidelines for the aging women are directed more toward increasing their ability to perform activities of daily living. Resistance training has even been shown to decrease risk of injury when proper guidelines are followed.

Even with everything that is known about resistance training and its benefits, there are still areas that can be improved. Future research has the potential to create new guidelines, increase results gained, and provide new ways to slow the decreases associated with aging. Research may even lead to guidelines that are specific for the female athlete.

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