Background: The purpose of this study was to identify the relationships between leg muscle power and sprinting speed with changes of direction.
Experimental design: the study was designed to describe relationships between physical qualities and a component of sports performance.
Setting: testing was conducted in an indoor sports hall and a biomechanics laboratory.
Participants: 15 male participants were required to be free of injury and have recent experience competing in sports involving sprints with changes of direction.
Measures: subjects were timed in 8 m sprints in a straight line and with various changes of direction. They were also tested for bilateral and unilateral leg extensor muscle concentric power output by an isokinetic squat and reactive strength by a drop jump.
Results: The correlations between concentric power and straight sprinting speed were non-significant whereas the relationships between reactive strength and straight speed were statistically significant. Correlations between muscle power and speed while changing direction were generally low and non-significant for concentric leg power with some moderate and significant (p<0.05) coefficients found for reactive strength. The participants who turned faster to one side tended to have a reactive strength dominance in the leg responsible for the push-off action.
Conclusions: The relationships between leg muscle power and change-of-direction speed were not consistent. Reactive strength as measured by the drop jump appears to have some importance for lateral change-of-direction speed, possibly because of similar push-off actions. It was concluded that reactive strength of the leg extensor muscles has some importance in change-of-direction performance but the other technical and perceptual factors than influence agility performance should also be considered.