Asymmetry in multi-directional jumping tasks

Objectives: Quantify and compare average symmetry indexes (ASI) across jumping directions (vertical, lateral and horizontal) and variables (jump distance and height, peak force and peak power) in a non-injured population of netball players. Methods: Nineteen sub-elite netball players (age: 19.5 +/- 1.1 years, body mass: 75.1 +/- 11.8 kg, height: 177.6 +/- 5.2 cm) performed three single-leg countermovement jumps from a force plate in the vertical, horizontal and lateral directions. Force, power and jump height ASI's were calculated from force plate data. Jump distance ASI was calculated as the distance jumped. Results: Individual ASI's ranged from 0.0 to 48.6% while averaged ASI's ranged from 3.1% (peak force) to 11.4% (peak power). Significant (p <= 0.05) ASI differences were observed between vertical force (3.0%) and power (9.2%) (p = 0.02), horizontal power (11.4%) and jump distance (4.6%) (p < 0.001), horizontal force (8.0%) and distance (4.6%) (p < 0.001) and lateral power (10.0%) and jump distance (6.2%) (p = 0.05). The greatest ASI was found for the lateral direction (8.4 +/- 1.2% averaged across the three variables). Conclusions: There appears to be some variation in the magnitude of the ASI depending on the variable and direction used to quantify the asymmetry. Decisions need to be made by the strength and conditioning practitioner as to which variables and directions are specific to the requirements of their sport, position or activity. (C) 2011 Elsevier Ltd. All rights reserved.