Melissa R. Iñigo1, 2 and Maria Fernandez-del-Valle3
Department of Health, Exercise, and Sport Sciences, Texas Tech University, Lubbock, TX, USA
8807 49th Avenue, College Park, MD 20740, USA
Department of Health, Exercise, and Sport Sciences, Texas Tech University, Exercise and Sport Sciences Building, 3204 Main, Lubbock, TX 49423, USA
Melissa R. Iñigo (Corresponding author)
Exercise participation implemented during childhood and adolescence may promote a continued active lifestyle later in life. This may then prevent the apparition of cardiovascular, metabolic, and other diseases known to be prevalent in young and older adults. Children and adolescents have unique exercise capacity characteristics. Thus, appropriate cardiovascular exercise guidelines were developed in order to receive maximum benefits from exercise training while also emphasizing safety. Furthermore, approaches to training with the youth were developed to promote exercise and sport adherence. This chapter focuses on cardiovascular exercise guidelines for children and adolescent women.
21.1 Learning Objectives
After completing this chapter, you should have an understanding of:
The importance of participating in physical activity is not limited to adults only. Establishing good health habits during the earlier stages of life may drive children and adolescents to continue to have an active lifestyle during adulthood . Indeed, researchers see a decline in physical activity participation rates during adolescence, and it continues to decline as individuals get older . This cultural trend can be combated if the promotion of a healthy lifestyle begins during childhood and adolescence because many habits are formed during this critical time .
The gains that children and adolescents obtain from exercise are plentiful. Through increased physical activity, specific muscular adaptations and enhancements in motor skill performance occur . Exercise also plays a role in skeletal health, prevention of excess body fat accumulation, and improvements in psychosocial health and well-being. This helps prevent osteoporosis, obesity, and other comorbidities that may develop later in life. Furthermore, regular participation in aerobic physical activity improves mood, self-appraisal, mental discipline, and socialization . Youth physical activity programs, including dynamic sports (swimming, gymnastics, rhythmic gymnastics, soccer, judo, etc.), have been shown to positively influence insulin sensitivity, lower total cholesterol and low-density lipoprotein levels, as well as improve performance measures (maximal oxygen consumption (VO2max), sprint speed, long jump, vertical jump, flexibility, agility, kicking distance, etc.) [3, 5–9].
Children and adolescents have a high exercise capacity relative to their body size. Some cardiorespiratory parameters are different between children, adolescents, and adults. Sex differences in exercise capacity also become apparent in children as they get older due to hormonal changes that adolescent boys and girls experience. These cardiorespiratory parameters are trainable. Children are able to improve their aerobic and glycolytic capacity through physical activity and supervised exercise training. Included in this chapter are cardiovascular exercise guidelines for children and adolescent women.
21.3 Research Findings
21.3.1 Children’s and Adolescents’ Unique Exercise Capacity Characteristics
The exercise capacity of children is unique. For instance, a child’s maximum oxygen consumption (VO2max) is relatively higher than at any other point in life if no further exercise training ensues (i.e. the individual remains untrained during adulthood) . VO2max, which refers to the maximum amount of oxygen (milliliters) the body can use (per kilogram of body weight), is an important indicator of cardiovascular fitness. A child has a high level of aerobic capacity relative to their body size. Regular exercise at a level that maintains a heart rate (HR) of about 170–180 beats per minute may increase VO2max in children. However, there is no evidence to suggest that the percent increase in VO2max through training is similar between children and adults . Absolute VO2max increases in both genders at the same rate during childhood (until the age of 12). Boys continue to increase at the same rate until the age of 17 or 18, but girls begin to plateau with very small increases after age 12. Between the ages of 17 and 22, women show a decrease in VO2max. This is attributed to a decrease in physical activity and an increase in adipose tissue during their adolescent years .
A relationship also exists between age and other cardiopulmonary parameters such as peak work rate, ventilation to carbon dioxide (VE/VCO2) slope, and HR recovery. Younger children have a lower peak work rate than adolescents . Moreover, the peak work rate of girls become increasingly lower compared to boys as they get older . Next, children have a higher VE/VCO2 slope than adults during exercise . VE/VCO2 slope represents ventilatory drive. an abnormally high VE/VCO2 slope may predict heart failure in patients with coronary heart disease. It is associated with decreased pulmonary perfusion, which leads to decreased oxygen availability, thus organ viability. In children however, the VE/VCO2 slope is normally higher than in adults because of relatively less efficient breathing during exercise . This slope decreases and normalizes to adult values as children get older. Furthermore, HR recovery is fastest in young children post-exercise . Generally, healthy children can recover quicker from intense exercise bouts compared to adolescent counterparts, which indicates enhanced vagal tone and fitness.
Metabolic cost is also relatively greater in children and adolescents than in adults. At age 5, the excessive metabolic cost is approximately 37 %. However, at age 17, the excessive metabolic cost is only 3 % . See Table 21.1 for factors that contribute to metabolic cost in children.
Possible causes of increased metabolic costs in children
Increased resting basal metabolic rate
Increased ventilatory costs
Higher stride frequency
Lower storage of elastic recoil forces
Locomotion style is biomechanically inefficient
Higher co-contraction of antagonist muscles
The glycolytic system of children and adults also differs significantly. When engaged in an activity that utilizes glycolysis (i.e., high-intensity short bout of exercise approximately 2–5 min), children show a lower level of performance compared to adolescents, who in turn show a lower level of performance when compared to adults. These decreases are thought to be the result of a smaller muscle mass, a lower glycolytic capacity, as well as a lack of neuromuscular coordination .
21.3.2 How to Approach Exercise with Children and Adolescents
Much of the activities that young children engage in should have an emphasis in enjoyment, peer-to-peer interaction, safety, age-appropriateness, and effectiveness. Being active should be enjoyable and something the children look forward to, for at their age, the fun factor promotes exercise adherence . This is especially important for girls because they are more inclined to significantly decrease their level of activity after they reach puberty . Children and adolescents also enjoy the social interaction during training sessions, games, and competitions, which is another important factor that encourages physical activity participation. Training programs for children must also be safe and guided by an expert so that under- or overtraining does not occur, and injuries can be prevented . For instance, weight-bearing activities are allowed provided that it is supervised. However, the child must also be both mentally and physically ready for the stress that strength training entails. Finally, exposing children to multiple physical activities and sports is far more beneficial in encouraging exercise and sport adherence . Specializing in one sport at such an early age (<15 years) may result in overtraining, burnout, and a less positive psychosocial development . Thus, for example, cross training during the active recovery period (1–3 weeks after the in-season) is recommended .
21.3.3 Cardiovascular Exercise Guidelines for Children and Adolescents
Children and adolescents should exercise at least 60 min per day at a moderate to high intensity for at least 3 days a week . For example, running, swimming, and playing are great activities for the youth. Nevertheless, aerobic activity should not be the only form of exercise in a child’s overall active lifestyle (see Chapter 22). Moderate-to-high intense activities are recommended in order to achieve the overall health benefits of physical activity and to improve motor performance skills of children. The standard metabolic equivalent (MET) is often used to precisely define the different exercise intensities. 1 MET refers to the energy (oxygen) used by the body at rest. Moderate intensity is typically between 3 and 4 METS, and high intensity is ≥7 METS. Such moderate and vigorous exercises may consist of continuous activity (60 min) or intermittent bouts (10, 20, or 30 min each). However, this depends on the goals of the individual as well. A child or an adolescent who is training for a particular organized sport or dance needs a well-designed periodized program that is specific to improving performance for that activity. Otherwise, the effectiveness of the program will not be optimal and can also promote injury. Other important guidelines are that exercise intensity and recovery period should be age-appropriate. The exercises should also be safe and well-supervised by an expert trainer or coach. Finally, the activities should be those that children and adolescents enjoy, and outside play with peers should be encouraged.
21.4 Contemporary Understanding of the Issues
When exposing children and adolescents to physical activity, their unique exercise characteristics are important to consider for safety reasons. The key point here is that the exercise program should not be as physically and mentally demanding as that in trained adults. This also increases the likelihood of children and adolescents adhering to exercise throughout their lifespan. The guidelines for cardiovascular exercise training are that children should participate in 60 min per day of at a moderate (3–4 METS) to high (7 METS) intensity (e.g. running, swimming, and playing other sports) .
21.5 Future Directions
Continuing research in physical activity is paramount in understanding how the body works and in developing a means to maximize health benefits and exercise performance.
One direction is to develop exercise guidelines specific for preadolescent female athletes. Currently, preadolescent female athletes have no guidelines of their own, despite their differences from males. Women experience an earlier onset of adolescent changes; therefore, it might be beneficial to develop different cardiovascular training guidelines to adjust for those changes during the preadolescent period.
In addition, the inclusion of functional exercises (strengthening the deep musculature of the trunk) into cardiovascular exercise programs may enhance cardiovascular exercise performance and prevent injuries (see Chap. 22). Future studies may also look at the benefits of multiple component training programs (i.e., strengthening, functional, and cardiovascular endurance training) in reducing injury, improving performance, and increasing exercise adherence in children and adolescent women.
21.6 Concluding Remarks
In this day and age, the importance of developing a healthy and active lifestyle from an early age cannot be stressed enough. The physical, health, and psychosocial benefits are plentiful. Maintaining an active lifestyle throughout one’s lifespan may be more likely if one starts participation and adheres to physical activity during childhood. Children and adolescents have unique exercise characteristics. Therefore, the cardiovascular exercise guidelines are different from adults. Strong emphasis is placed on enjoyment, social interaction, safety, age appropriateness, and effectiveness.
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