With the increasing concern of rising obesity levels, more and more attention is being turned to encourage young people to become physically active. Here, we look at the differences in physiological response to exercise between young people and adults.
Many adolescents already take part in physical activity or sport regularly, and are already reaping the benefits of being physically fit at a young age. Such benefits include:
- An increase in bone density
- Increased likelihood of participation to continue into adulthood
- Having a lower incidence of injuries
- Weight management
- Improvement in asthma symptoms and cholesterol levels
- Being physically fit enables an athlete to maximize their potential in sport
With greater numbers participating in more than one sport and taking part in competitions frequently, of concern to many fitness professionals, parents and youngsters alike is the amount of training young people of this age are undertaking. We all know their bodies are undergoing rapid change, and consequently we need to be particularly cautious about ever increasing intensities in sports competitions. A number of different factors need to be taken into account before any training program is designed for these athletes and below are a few helpful pointers to guide fitness professionals in the right direction.
Exercise and Growth
Boys and girls have different growth spurts whereby girls undergo their adolescent growth spurt and peak velocity height about two years earlier than boys. However, boys experience longer growth spurts that are more intense than girls2 and they tend to overtake the growth period of females during this life stage. Training therefore needs to take into consideration these differences and fitness professionals need to ensure that individual recognition takes place where no child is undertaking a program too strenuous or intense for their physical development.
Energy and Fluid Needs
Although there is mounting evidence among adults that daily energy requirements are related to total amount of training, there is a limited amount of information in this area for children participating in specific sports. Of the available research, when energy cost is calculated per kg body mass, walking or running at any given speed is significantly greater in children than in adolescents and adults, and this relative cost is higher the younger the child. For example, a seven-year-old child who is walking or running at the same speed as a young adult would need as much as 25 to 30 percent more energy per kg body mass.3 As a result of their greater energy needs while performing physical activities, children also produce more metabolic heat per unit body mass than adults. Consequently, fluid intake must reflect such production and as core body temperature during dehydration increases faster in children than in adults,4 it is vital for coaches and trainers to try to prevent dehydration in child athletes. An ideal approach is to introduce fluid breaks every 15 to 20 minutes during prolonged activities.
Sub-maximal cardiovascular responses are different between children and adults, with children tending to work at a higher heart rate at sub-maximal levels of exercise. Children have smaller hearts and less total muscle volume than adults and therefore any such cardiovascular training should account for such differences. Oxygen extraction by the tissues (a-VO2 diff) also tends to be slightly larger in children than in adults, so it is important to remember that if exercising on hot days, children's core body temperature will increase more rapidly. Ensuring children are fully hydrated will help reduce the negative effects of such increases.
After the age of 14, girls' aerobic power can be as much as 15 percent less than boys. However, the effect of endurance training programs on VO2 max on both genders has proved inconclusive.2 This may be due to other growth factors playing a more significant role, such as greater musculature or larger levers, which dominate the effectiveness of aerobic activities.
As expressed per kg of bodyweight, anaerobic capacity is much lower in children than adults and increases progressively with age in both boys and girls. It is important therefore to be aware of the intensity of exercise regimes, as it is not the duration but the intensity of exercise that could lead to more harm. Appropriate activities would include long-distance runs instead of vigorous short sprints, as these may also aid in meeting appropriate body composition requirements.
After the adolescent growth spurt, muscle development is influenced by hormones and, since testosterone production is greater among males, they will become stronger and faster than females. For such boys, however, it is important to not put too much strain on the body. Two times per week has been proven to ensure significant changes, compared to more frequent sessions where no further improvement was found.3 Activities should be based on individual bodyweight and restrictive weight exercises on machines should be avoided.4 Below are a few recommendations of how to incorporate strength training into young athletes’ regimes. The exercises should be progressive: starting at one and, as the adolescent develops, moving them up through to five.
- Obstacle courses: rope pulling, climbing
- Vertical strength: standing push-ups, hanging exercises
- Bodyweight exercises and medicine ball-based activities/throws
- Horizontal strength: push-ups, pull-ups
- Single leg squats, step-ups, dumbbells and barbell exercises
All sports, no matter what discipline, require a high level of skill in order to excel. However, specialized training too early on in adolescence can actually have more of a negative than positive effect. Movement skills such as balance, agility and coordination which would usually be developed as part of a broader based program become neglected and as a result can leave the young athlete with little competency outside the speciality.
Peak Velocity Height (PVH)
Sports scientists believe that it can take up to 12 years of training for a young talented athlete to reach elite status. The use of athletic models to develop these athletes has been successful in recent years. However, due to differences in physical, cognitive and emotional development, research states that age is not a good indicator on which to base athletic development models for athletes between the ages of 10 to 16. Instead, the onset of peak velocity height (PVH) is recommended, which is the point where a child reaches their maximum growth rate. This is affected by genetic and environmental factors (climate, cultural and social) and can be an advantageous reference point for training program design. PVH for girls is usually around age 12 and for boys, age 14. By taking basic measurements (standing height and sitting height), PHV can be observed and specific training programs can be designed to match the child's development.
Much debate has surrounded the question of whether young sportspersons should specialize in particular sports at an early age. Current evidence suggests that adolescents should participate in activities that develop overall capacities rather than specialized programs. Furthermore, research has found that when development of strength, power and flexibility is undertaken gradually, higher levels are achieved and the maintenance of such factors remain for longer periods of time. Since growth rates of male and female adolescents vary considerably, it is important that a comparison between athletes is avoided. Certain individuals will improve rapidly on some exercises, while others who have not gone through a particular growth phase will often lag behind. On a personal level, young athletes may also feel confined to the realms of one sport if they specialize too early, which may have a negative effect on participation levels. By experiencing a range of activities and training programs, the young person is more likely to develop a range of athletic abilities, which will increase their options to specialize later on.
- Borms J (1986), The Child and exercise: an overview, Journal of Sports Sciences, 4, 3-20.
- Drabik J (1996), Children and Sports Training: How Your Future Champions Should Exercise to Be Healthy, Fit, and Happy , Island Pond, VT: Stadion Publishing Company, Inc.
- Overend T, Paterson D, Cunningham D and Taylor A (1985), Interval and continuous training: A comparison of training effects. A paper given at the Annual Meeting of the Canadian Association of Sports Sciences, Laval University, Quebec.
- Rushall B, Marsden J and Young C (1993), A suggested program of foundational conditioning exercises for age-group swimmers: a manual for coaches, NSWIMMING Coaching Science Bulletin, 2(1), 1-23.
- Stahle S, Roberts S, Davis B and Rybicki L (1995), Effect of a 2 versus 3 times per week weight training program in boys aged 7 to 16, Medicine and Science in Sports and Exercise, 27(5), Supplement abstract 648.