The Effects of an Isometric Quarter Squat on Countermovement Jump Performance

The purpose of the study was to determine if an isometric quarter squat was sufficient to elicit postactivation potentiation (PAP) in a countermovement jump (CMJ) for recreationally trained individuals (n = 22). The isometric quarter squat conditioning stimulus consisted of three sets of six second maximal voluntary contractions against a custom made apparatus. The conditioning stimulus was designed to acutely enhance CMJ performance by stimulating PAP, in turn improving indicators of CMJ performance which included eccentric rate of force development (ERFD), mean rate of force development (MRFD), peak rate of force development (PRFD), reactive strength index (RSI), and peak power (PP). CMJ performance was tested at one, five, ten, and fifteen minutes post-conditioning stimulus to identify the optimal recovery time for optimal performance. Statistical analysis was carried out using a two-way repeated measures analysis of variance (ANOVA) and no significant or meaningful change was found in ERFD, MRFD, PRFD, RSI, or PP. The overall power was small for all variables suggesting that the ability of the current study to observe an effect that might have existed was very unlikely. Effect size was also small in all variables suggesting that the change pre to post-testing was not meaningful. Some critical factors that may have contributed to the results included the individual’s ability to potentiate, body positioning during conditioning stimulus, and level of conditioning of subjects