Reliability of a Unilateral Horizontal Leg Power Test to Assess Stretch Load Tolerance

Abstract

Drop jumping has previously been used to measure fast stretch shorten cycle (SSC) ability and stretch load tolerance. To the knowledge of these authors a test does not exist to achieve this in the horizontal direction. The purpose of this study therefore was to estimate the reliability of a new unilateral horizontal leg power test to assess these qualities. Participants (N = 10) performed three jumps on each leg from distances of 80%, 120%, and 160% of leg length onto a force plate, followed immediately by a jump for maximal distance onto a synthetic track. No significant between- leg differences (p > .05) were found for the dependent variables of ground contact time (GCT), peak propulsive vertical ground reaction force, peak propulsive horizontal ground reaction force, and distances jumped (DJ).Within-trial variability (coefficients of variation) ranged from 3.6% to 10.9%, and test-retest reliability intraclass correlation coefficients from 0.80 to 0.95. GCT and DJ were the variables with highest reliability between trials and days. These two variables should be used to indicate fast SSC (GCT) ability and stretch load tolerance (DJ-GCT) in the horizontal direction. The relationship of these measures to functional performance needs to be established.