The relationship between the human motor performance domains of leg strength and speed of body movement

The purpose of this study was to determine the relationship between selected multiple tests of leg strength and speed of body movement. A review of literature presented and discussed findings of the factor structure of leg strength and body speed. In addition, the relationships between various leg strength and body speed variables, as determined through bivariate correlation, analysis of variance, multiple regression, and canonical correlation, were reported and evaluated. Subjects utilized in this study included 169 sixth and seventh grade boys who were tested during a two-week period. Each subject was measured on the static leg strength tests of knee extension, hip extension, and ankle plantar flexion; leg power tests of the bicycle ergometer and Margaria power index; sprinting speed tests of acceleration (0-10 yards) and velocity (10-30 yards); controlled speed tests of the right boomerang and dodge run; and jumping speed tests of the box jump and vertical jump. Also, eleven anthropometric measures were determined for each subject. The factor analysis of the anthropometric variables yielded body fat and maturity factors. Two analytic strategies were used in this study. One utilized raw scores, the other, residual scores. The effects of the eleven anthropometric variables, the body fat and maturity factors, were removed from the raw scores to form the residual scores. Because a part of the error variance of the experimental variables was accounted for by individual differences associated with body fat and maturity, a clearer picture of the relationship between the two sets of experimental variables was gained by using the residual scores. When the raw scores were factor analyzed, two factors were derived: leg strength, which included all the strength measures; and speed of body movement, which included all the speed measures. The bicycle ergometer test, a leg strength measure, loaded on both derived factors, but considerably higher on the leg strength factor. Sprint acceleration, a body speed measure, also loaded on both factors, but much higher on the speed of body movement factor. Factor analysis of the residual scores produced the same two factors of leg strength and speed of body movement, with the bicycle ergometer and sprint acceleration loading as they did in the raw score analysis. In addition, the analysis of the residual scores produced a task specific third factor composed of one leg strength measure, ankle plantar flexion, and one body speed measure, the box jump. Canonical correlation results of both raw and residual scores indicated a significant relationship between linear combinations of the leg strength and speed of body movement domains. In addition to providing the clearer picture of the relationship between the two domains, the residual scores also produced a higher correlation coefficient than the raw scores. The primary contributors to the significant correlation were two leg strength tests, the bicycle ergometer and Margaria power index, and one body speed test, sprint acceleration. Although a significant relationship between leg strength and speed of body movement was found in this study, it was concluded that additional extraneous variables need to be controlled in the quest to determine the "true" relationship between leg strength and body speed. Based on these additional variables, suggestions for future research were presented.