Bilateral comparison of propulsion mechanics during single-leg vertical jumping.

The primary purpose of this investigation was to compare single leg vertical jump performance and several performance characteristics derived from vertical ground reaction forces (vGRF) between the dominant (DOM) and nondominant (NDOM) legs. Secondary purposes included determining the relationship between the kinetic and temporal characteristics and single leg vertical jump performance and establishing the intrasession and intersession reliability of the characteristics considered. After a standardized warm-up, 20 physically active young adults (10 men, 10 women) performed three single leg DOM and three single leg NDOM vertical jumps in a random order during two sessions separated by three days. vGRF collected during each trial were used to calculate jump height, peak vertical power, peak vGRF, vGRF impulse, ratio between negative to positive vGRF impulse, time between maximum peak power to takeoff and countermovement depth. There were no significant differences between DOM and NDOM for jump height (p = .145) as well as the six characteristics considered (p > .05). There was a strong, direct relationship between jump height and peak vertical power for both DOM (r = .915, p < .001) and NDOM (r = .944, p < .001). With the exception of vGRF negative/positive impulse ratio, all dependent variables demonstrated moderate to high intrasession and intersession reliability. These results support using a single leg vertical jump protocol for conducting bilateral lower extremity functional assessments. With the exception of impulse ratio, the reliability results support using the protocol for serial assessments. In conclusion, healthy individuals can be expected to exhibit near equal single leg vertical jumping performance bilaterally, providing practitioners with a basis to interpret performance.