The purpose of this study was to examine the effect of 2 school years (21 months) of a twice-weekly resistance training program on stature, muscle strength, and self-concept among prepubertal boys. The experimental group (E, n = 27) aged 9.2 ± 0.3 yrs, participated in progressive resistance training, while the control group (C, n = 22) aged 9.4 ± 0.3 yrs, participated in standard physical education classes (as advised by the Ministry of Education). Training sessions included 1–4 sets of 3–6 exercises, with 5–30 repetitions/set. The load ranged between 30% and 70% 1RM. No differences were observed in the gain in body height between groups. Muscle strength increased significantly more in E (e.g., knee extensors: 0.51 ± 0.13 to 0.77 ± 0.16 kg/kg body mass), compared with C (0.34 ± 0.12 to 0.54 ± 0.11 kg/kg body mass). One minor injury was reported throughout the study. Initial scores of self-concept were high in both groups, with no training effect. The results demonstrate that among prepubertal boys, a twice-weekly low-to-moderate-intensity resistance training program over a period of 2 school years (21 months) can result in enhancement in muscle strength with no detrimental effect on growth.
E. Sadres was with the Nat Holman School of Coaches and Instructors and is presently with the Zinman College of Physical Education and Sport Sciences, Wingate Institute, Netanya, Israel; A. Eliakim is with the Department of Pedatrics, Meir Hospital, Kfar Sava, Israel; N. Constantini and B. Falk are with the Ribstein Center for Sport Medicine Sciences and Research, Wingate Institute, Netanya, Israel; R. Lidor is with The Motor Behavior Laboratory, The Zinman College of Physical Education and Sport Sciences, Wingate Institute, Netanya, and Faculty of Education, Haifa University, Israel.