The relative contribution of strength and physique to running and jumping performance of boys 7-11.

The purpose of this study was to determine the association of static strength with motor performance of 7 through 11 year old boys (N = 60) after accounting for differences in physique, i.e., body size, shape, and composition. Static strength measures included thigh extension, leg extension and plantar flexion measured by electronic transducer and back lift, leg lift, and right and left grips measured by spring dynamometer. Measures of body composition consisted of fat estimated from triceps, subscapsular and calf skinfolds, and fat-free body weight estimated from potassium-40 measurements. Body structure consisted of skeletal widths, and segment girths, lengths and volumes. The dependent variables were vertical jump, standing broad jump, 50-yard dash, 600-yard run and mile run. The measures of strength increased the variance accounted for from 10 to 23% over that when body size, composition and structure were used without strength. An exception was vertical jump where no increase in the variance accounted for was found with the addition of strength variables. The regression equations determined for the sample of 60 boys rendered multiple R's ranging from 0.64 (mile run) to 0.75 (50-yard dash). It was concluded that strength has a significant relation to motor performance and that its contribution can be better assessed after accounting for differences in body size, shape, and composition.