Currently, variables predictive of vertical jumping performance can account for only part of its total variability. A potential additional source of variation called explosive strength deficit (ESD) was described in 1995 by Zatsiorsky (Science and Practice of Strength Training. Champaign, IL: Human Kinetics, 1995. pp. 34-35.). ESD is determined by measuring the maximum force generated under ideal circumstances (Fmm) and under task-relevant conditions (Fm). It is calculated as 100(Fmm Fm)/Fm. For this study, the following operational definitions were used: Fmm = squatting peak force at 0.51 m·s1; Fm = squatting peak force at 1.43 m·s1. Data were analyzed using forward stepwise multiple regression. Mean ESD for men was 29.7% (SD = 11.7) and for women was 49.3% (SD = 11.2). For men and women, respectively, zero-order correlations for ESD with restricted vertical jumping (RVJ) distance were 0.35 and 0.60, and between ESD and drop vertical jumping (DVJ) distance were 0.20 and 0.63. However, when the previously identified predictors were taken into account, ESD was not a significant predictor (p > 0.05) of either type of jump. Therefore, it was concluded that ESD on the basis of velocity-regulated squats does not augment the explained variance previously established for vertical jumping performance.
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