Research on the growth, developement and trainability in muscle strength for the prepubescents

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The purpose of this study was to determine the effect of strength training in prepubescent boys and girls on muscle strength and cross-sectional area of upper arm muscle. Subjects were ninety-nine healthy elementary school children who belonged foist, 3rd and 5th grades and they were assigned to two groups of training (N=52) and control (N=47). Training group participated in strength training program for 12 weeks which consisted of maximum sustained isometric contraction of elbow flexion for ten sec, whereas control group did not participate in special training program in this period. In order to determine the changes due to training, cross-sectional areas of the tissues in upper arm, such as the whole tissue, muscle, fat and bone, were measured by the ultrasonic methods. Maximum isometric and isokinetic muscle strengths of elbow flexion and extension were measured by means of isokinetic cybex dynamometer. In order to assess the development of physological maturity. TW2 method was used … More to estimate the skeletal age in each subject by taking the hand-wrist X-ray photograph. After 12-week training period, the cross-sectional area of the whole tissue significantly increased in both training (2.52 cm^2, 8.9%) and control groups (2.11 cm^2, 7.3%). This increase was due to significant increases in muscle and bone areas in the training group and, on the other hand, due to the significant increase only in fat area in the control group. In the training group increase In muscle area was about 50% of that derived from the study on adults (Fukunaga, 1978). The increment in cross-sectional area of muscle with training was significantly correlated with the skeletal age (r=O.36, p<O.Ol). Isometric strength of elbow extension showed significant increase (1.17 kg, 17.5%) and for 5th grade males this increase was about 40% of that obtained from adults, whereas isokinetic strength unchanged with training. Muscle strength per cross-sectional area did not show a significant increase except the training group of 5th grade boys. In conclusion, the effects of strength training on cross-sectional muscle area and muscle strength for prepubescents were similar in its direction to but different in its magnitude from those found in adults. Less