Effects of resistance training on protein utilization in healthy children

PIKOSKY, M., A. FAIGENBAUM, W. WESTCOTT, and N. RODRIGUEZ. Effects of resistance training on protein utilization in healthy children. Med. Sci. Sports Exerc., Vol. 34, No. 5, pp. 820–827, 2002. Purpose Public health initiatives promote increased physical activity in children. More specifically, resistance training has recently received attention as an important component of youth fitness programs. The study examined the effect of this mode of exercise on protein utilization in young boys and girls. Methods Healthy children (N = 11, 8.6 ± 1.1 yr, 33.7 ± 9.4 kg, 131 ± 9.6 cm, BMI = 19.1 ± 3.4) participated in a supervised resistance-training program 2 times·wk−1 for 6 wk. 15N glycine methodology was used to assess nitrogen flux (Q), protein synthesis (PS), protein breakdown (PB), and net turnover ([NET] = PS − PB) before (PRE) and after (POST) resistance training. Percent body fat (%BF), fat-free mass (FFM), fat mass (FM), and energy and protein intakes were also determined. PRE/POST measurements of 1RM for the chest press and leg extension were used to examine strength gains. Results Gains associated with the chest press and leg extension were 10% and 75% (P < 0.001), respectively. Significant increases (P < 0.05) were noted for weight, height, FFM, and FM. Energy and protein intake remained constant. Significant decreases (PRE vs POST) were observed for Q (1.22 ± 0.1 vs 0.75 ± 0.05 gN·kg−1·d−1, P < 0.001), PS (6.48 ± 0.47 vs 3.55 ± 0.30 g·kg−1·d−1, P < 0.001), and PB (5.24 ± 0.41 vs 2.96 ± 0.30 g·kg−1·d−1, P < 0.01) after 6 wk of resistance training. NET was also reduced (P = 0.07, 1.24 ± 0.31 vs 0.59 ± 0.20 g·kg−1·d−1). Conclusions Resistance training resulted in a downregulation in protein metabolism, which may be energy based. Future studies are needed to clarify energy, as well as protein, needs in young children participating in this form of exercise.