Special Considerations
Fitness Training in Children
The results from studies examining the effects of endurance training for children are not always in agreement. Factors confounding the interpretation of results include poorly-quantified training protocols, variations in age, sex, and maturation, and differences in early fitness levels. Even with those limits in mind however, the consensus is: endurance training positively influences the aerobic fitness of children.
Cross-sectional studies on experienced child swimmers found the average VO2max of the swimmers was significantly greater than untrained children of similar ages. Consistent with these findings, others reported increased aerobic fitness in child runners, swimmers, hockey players, and wrestlers.
Some investigators, however, have not found increases in aerobic fitness after exercise training. Stewart and Gutin found no significant VO2max changes in boys 10 to 12 years of age after 8 wk of interval training. Bar-Or and Zirwin found an increase in the frequency of physical education classes over a 9 wk period had no effect on the VO2max of 9 and 10-year-old boys. Others report no significant increase in VO2max or cardiovascular fitness, after endurance training in children. Some of these results however, are open to question because the training program was not of enough intensity or duration. Because prepubertal children are inherently active, they may have a higher threshold level for training effects. Training-induced increases in VO2max may only happen when training intensity and duration are high.
Another reason for these dissident results may be an apparent maturation-related sensitivity of training responses. Schmucker and Hollmann examined well-trained juvenile male and female swimmers, cyclists, and field hockey players, and found an increase in endurance training did not affect the aerobic capacity in athletes less than 11 years of age. Male athletes older than 12 years however, did show aerobic capacity increases, although the effect in females was less obvious.
Comparisons between the effects of endurance training in adults and in children are similar. For example, endurance-trained 12 to 13 year old girls and 18 to 21 year old women, using running and bench-stepping methods had similar VO2max increases after 14 weeks. It appears endurance training of enough intensity and duration can increase the aerobic fitness of children and adolescents. And, the training responses of adults and children appear similar, when training programs are of adequate intensity, but in children, especially males, endurance training adaptations may be sensitive to maturational changes.
Resistance exercise benefits can also be realized by adolescent athletes. Although resistance exercise training in prepubescent has been discouraged as recently as 1983, recent evidence suggests similar beneficial results can be obtained by prepubescents, pubescents and postpubescents. Furthermore, the American Orthopedic Society for Sports Medicine notes resistance training can increase muscular strength and endurance, improve motor skills, prevent injury, and have positive psychological benefits in youngsters. The society recommends however, equipment be developed to better fit the size of the prepubescent, prepubescents not participate in competitive lifting programs, repetitions remain above 6, proper warm-up and cool-down periods be utilized, and all training include adequate instruction and supervision.
There is some discussion about the frequency, necessary depth, and usefulness of preparticipatory physical exams, however, most agree physical exams given before initial sports participation (middle and high school), and again during high school, are recommendable. Preparticipational physical exams should be given to all children starting an endurance training program who have not been examined earlier, and especially those who may be at a high risk because of prior injury or disease. Information collected from these exams can be useful for excluding or modifying exercises which otherwise, may be contraindicated.
Although regular, vigorous exercise should be encouraged in children, certain special precautions should be appreciated. For example, thermoregulation in children during heat exposure is less efficient than in adults. Because children are more prone to heat injury than adults, they should be closely monitored during endurance activities with heat exposure. Other concerns among exercise specialists are the effects of competitive endurance activities on growth. Currently, there are no compelling data that endurance training will either limit or enhance growth; however, animal studies have shown exercise can significantly influence the modeling and remodeling of connective tissues. Unfortunately, exercise training of optimum intensity, duration, and frequency for children has not yet been defined. Thus, periodical and systematic evaluations of the young athlete are needed to ensure improvement or maintenance of fitness without exacerbating the risk of injury.
Fitness Training in Women
It is generally agreed the benefits afforded from exercise are similar for men and women.
Endurance parameters such as VO2max, cardiac output, and submaximal heart rate, show similar improvements for males and females with aerobic training. Furthermore, although muscular strength is generally greater in males than in females, relative strength increases from resistance training do not show sex-related differences. Muscle hypertrophy from resistance training, however, is greater in males than in females. It is believed this difference is due to the 20 to 30 times higher testosterone levels of males.
Exercise-related amenorrhea and menstral irregularity are important concerns among women athletes. The exact causes of exercise-related amenorrhea and menstral irregularity appear to be confounding related to increases in activity, decreases in body weight and fat composition, and nutritional and psychological factors. Because amenorrhea can predispose female athletes to musculoskeletal injuries (e.g. stress fractures), and hormonal imbalances, failure to menstrate or cessation of the normal cycle should be evaluated by an experienced physician.
Fitness Training in the Elderly
The benefits of regular exercise in the elderly include:
(1) maintenance of functional capacity and independent living
(2) reduced risk of cardiovascular disease
(3) retardation of the progression of chronic diseases
(4) promotion of social interaction
(5) psychological benefits
Unfortunately, the physiological changes occuring with aging are variable and may limit exercise prescription. These age-related changes include increased risk of cardiovascular disease, decreased aerobic parameters, decreased heat tolerance, decreased muscular strength, decreased flexibility, and decreased joint mobility. Additionally, there is a higher prevalence of diabetes mellitus, hypertension, malnutrition, and degenerative bone and joint disease in the elderly.
Because of the high degree of variability among elderly, individualization of exercise prescription is essential and should be based upon the health status and goals of the participant. All exercise prescription in the elderly should be preceded by a systematic assessment of the participant's health and fitness status.
Although the need for routine exercise has become increasingly appreciated by the elderly in recent years, most current exercise programs fail to address a very important aspect of physical fitness the progressive loss in strength occuring with aging. Loss of strength, in the elderly, severely limits the functional capacity of men and women, and reduces their ability to lead independent lives. The detrimental muscular changes occuring with aging include decreased muscle mass, decreased muscle activation, decreased contraction speed, and decreased muscular strength. The mechanisms responsible for these impairments include progressive inactivity in addition to the purely physiological effects of growing older.
Traditionally, exercise prescription for the elderly has relied on aerobic activities such as walking and jogging. Unfortunately, while these exercises improve cardiovascular performance, they do not address another equally important component of fitness muscular strength. Furthermore, continual repetitive exercises of this nature can produce intra-articular damage related to overuse, and subjects who are overweight or have osteoarthritis are especially susceptible to these types of injuries.
Can people of advanced age increase their muscular strength through resistance training? To date, evidence supports the contention proper resistance exercises promote muscle hypertrophy and increase muscular strength in the elderly. Frontera and coworkers found leg strength increased up to 227% in 60-72 year-old men, after only 12 weeks of resistance exercise. Muscle mass was also increased, in this group of individuals. Aniansson and Gustafsson found men (69-74 year-old), using only the weight of their legs during extension exercises, increased their quadricep muscle strength up to 22%.
Submaximal heart rate (a cardiovascular indicator) was also significantly decreased in these individuals. The investigators concluded "aging human skeletal muscle remains trainable and the training response is similar to that seen in younger age groups." Others have also reported increased muscle mass and muscular strength in resistance trained seniors.
Some researchers have even shown muscle in elderly subjects repairs itself exceptionally well, even after weightlifting exercises using excessive loads. Clarkson and Dedrick found for physically active women over 60, the muscular repair process following extreme resistance exercise was similar to college-age women. They concluded "older muscle has the same ability to adapt to damage as young muscle." Lastly, beneficial neurological adaptations have also been reported for resistance trained seniors. Moritani and deVries showed specific neurological function can be dramatically improved in older subjects after only 8 weeks of resistance training. Furthermore, the neurological adaptations which occurred during the training period significantly increased muscular strength. In all of the studies cited above, no detrimental effects of resistance training in the elderly were reported. Thus, properly designed and monitored resistance training programs can significantly improve muscle function, muscle hypertrophy, muscular strength, and neurological function in the elderly.
References
American College of Sports Medicine: Guidelines for Graded Exercise Testing and Exercise Prescription, Philadelphia: Lea and Febiger, 1991.
American Orthopaedic Society for Sports Medicine. Proceedings of the conference on strength training and the prepubescent. B. Cahill, 1988.
Aniansson, A. & E. Gustafsson. Physical training in elderly men with special reference to quadriceps muscle strength and morphology. Clin. Physiol. 1:87-98, 1981.
Bar-Or, O. Pediatric Sports Medicine for the Practitioner. New York: Springer-Verlag, 1983.
Benedict, G., P Vaccaro, & B. Hatfield. Physiological effects of an eight-week precision jump rope program in children. Am. Correct Ther J-5:108 111, 1985.
Blum, R. W. Preparticipation evaluation of the adolescent athlete. Postgrad. Med. 78:52 69, 1985.
Clarkson, P. M. & M. E. Dedrickh. Exercise-induced muscle damage, repair, and adaptation in old and young subjucts. J. Gerontol. 4:M91-96, 1988.
Cunningham, D. A., P. Telford, G. T. Swart. The cardiopulmonary capacities of young hockey players: Age 10. Med. Sci. Sports 8:23 25, 1976.
Eisenman, P. A., and L. A. Golding. Comparison of effects of training VO2max in girls and young women. Med. Sci. Sports 7:136 138, 1975.
Frontera, W. R., C. N. Meredith, K. P. O'Reilly, H. G. Knuttgen, and W. J. Evans. Strength conditioning in older men: skeletal muscle hypertrophy and improved function. J. Appl. Physiol. 64(3):1038-1044, 1988.
Haupt, H. Strength training. Sports Medicine the School-Age Athlete, ed. Reider, B., Philadelphia, PA, W.B. Saunders, 1991.
Klitgaard, H., M. Mantoni, S. Schiaffino, S. Ausoni, L. Gorza, C. Laurent-Winter, P. Schnohr, & Saltin. Function, morphology, and protein expression of ageing skeletal muscle: a cross-sectional study of elderly men with different training backgrounds. Acta Pysiol. Scand. 140:41-54, 1990.
McArdle, W. D., F. I. Katch, and V. L. Katch. Exercise Physiology: Energy, Nutrition, and Human Performance. Phila., PA: Lea and Febiger, 1986.
Moritani, T. and H. deVries. Potential for gross muscle hypertrophy in older men. J. Gerontol. 5:672-682, 1980.
Rowland, T. Preparticipation sports examination of the child and adolescent athlete: Changing views of an old ritual. Pediat. 13:39, 1986.
Sady, S., W. Thompson, K. Berg, & M. Savage. Physiological characteristics of high-ability prepubescent wrestlers. Med Sci Sport Exerc.16:72 76,1984.
Schmucker, B., and W. Hollman. The aerobic capacity of trained athletes from 6 to 7 years of age on. In: Children and Exercise, J. Borms, M. Hebbelinck (Eds.), Acta Paediat. Belgica (Suppl.) 28:92 101, 1974.
Stewart, K., & B. Gutin. Effects of physical training on cardiorespiratory fitness in children. Res. Quart. 47:110 120, 1976.
Vaccaro, P., D. H. Clarke, and A. F. Morris. Physiological characteristics of young well-trained swimmers. Europ. J. Appl. Physiol. 44:61 66, 1980.
Zernicke, R. F., G. Salem, & R. Alejo. Endurance training. Sports Medicine the School-Age Athlete, ed. Reider, B., Phila., PA, W.B. Saunders, 1991.
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