RESUMO
The purpose of this study was to investigate the optimal starting period of muscle power training during growth. Thirty-three Wistar strain male rats were used and classified into four groups, control group, 3T group started a training at 3 weeks after birth (weaning period), 8T group started a training at 8 weeks after birth (puberty period) and 13T group started a training at 13 weeks after birth (beginning of mature period) . Each training group was subjected to a power sprint training till 23 weeks after birth (mature period) .<BR>The results were summarlized as follows;<BR>1) Hypertrophy and increase of contractile properties in muscle were not seen in each training group.<BR>2) Muscle glycogen contents increased significantly in 3T group (p<0.05) and in 8T, 13T group (p<0.01) .<BR>3) Muscle fiber area increased significantly in 8T group only.<BR>4) Phosphofructokinase activity in muscle increased significantly in 8T group only.<BR>These results suggest that 8 weeks after birth, the puberty period may be the most effective starting period of power sprint training during growth in rats.