The Physiology of Youth Exercise Training Gains
By John R. Mishock, PT, DPT, DC


When children and adolescent see gains in parameters involving strength, power and speed it appears that those changes have strong neurological mechanisms rather than a hypertrophic (increase muscle mass and girth) factors. (1, 2, 3, 4)

During puberty; testosterone, growth hormone and insulin-like growth factors secretion allow males to see considerable increases in hypertrophic muscle mass and linear growth. (5) Training-induced strength gains during and after puberty in males may therefore may be associated with changes due to hormonal influences on the muscle. In females there are smaller amounts of testosterone thus limiting the magnitude of training-induced increases in muscle hypertrophy. (6, 7)

It appears that the strength, power and speed changes seen in preadolescence are due to neural adaptations (i.e., increased motor unit activation and changes in motor unit coordination, recruitment, and firing; motor skill development) and possibly intrinsic muscle adaptations (increases in muscle torque). Thus, during the training significant observable gains of muscle hypertrophy and mass may not be evident. (7, 8, 9, 10)

1. Sale, D. Strength training in children. In: Perspectives in Exercise Science and Sports Medicine. G. Gisolfi and D Lamb, eds. Indianapolis, IN: Benchmark Press, 1989. pp. 165-216.
2. Ramsay, J, Blimkie, C, Smith, K, Garner, S, Macdougall, J, and Sale, D. Strength training effects in prepubescent boys. Med Sci Sports Exerc 22: 605-614, 1990.
3. Ozmun, J, Mikesky, A, and Surburg, P. Neuromuscular adaptations following prepubescent strength training. Med Sci Sports Exerc 26: 510-514, 1994.
4. Malina, R. Weight training in youth-growth, maturation and safety: An evidenced based review. Clin J Sports Med 16: 478-487, 2006.
5. Kraemer, W, Fry, A, Frykman, P, Conroy, B, and Hoffman, J. Resistance training and youth. Pediatr Exerc Sci 1: 336-350, 1989. Rowland, T. Children’s Exercise Physiology (2nd ed.). Champaign, IL: Human Kinetics, 2005. pp. 181-195.
6. Sale, D. Strength training in children. In: Perspectives in Exercise Science and Sports Medicine. G. Gisolfi and D Lamb, eds. Indianapolis, IN: Benchmark Press, 1989. pp. 165-216.
7. Rowland, T. Children’s Exercise Physiology (2nd ed.). Champaign, IL: Human Kinetics, 2005. pp. 181-195.
7. Ramsay, J, Blimkie, C, Smith, K, Garner, S, Macdougall, J, and Sale, D. Strength training effects in prepubescent boys. Med Sci Sports Exerc 22: 605-614, 1990.
8. Rians, C, Weltman, A, Cahill, B, Janney, CA, Tippet, S, and Katch, F. Strength training for prepubescent males: Is it safe? Am J Sports Med 15: 483-489, 1987.
9. Ozmun, J, Mikesky, A, and Surburg, P. Neuromuscular adaptations following prepubescent strength training. Med Sci Sports Exerc 26: 510-514, 1994.

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