Cross-validation of three jump power equations

The vertical jump-and-reach score is used as a component in the estimation of peak mechanical power in two equations put forth by Lewis and Harman et al. Purpose: The purpose of the present study was to: 1) cross-validate the two equations using the vertical jump-and-reach test, 2) develop a more ac curate equation from a large heterogeneous population, 3) analyze gender di fferences and jump protocols, and 4) assess Predicted Residual Sum of Squar es (PRESS) as a cross-validation procedure. Methods: One hundred eight coll ege-age male and female athletes and nonathletes were tested on a force pla tform. They performed three maximal effort vertical jumps each of the squat jump (SJ) and countermovement jump (CMJ) while simultaneously performing t he vertical jump-and-reach test.:Regression analysis was used to predict pe ak power from body mass and vertical jump height. Results: SJ data yielded a better power prediction equation than did CMJ data because of the greater variability in CMJ technique. The following equation was derived from SJ d ata: Peak Power (W) = 60.7 X (jump height [cm]) + 45.3 X (body mass [kg]) - 2055. This equation revealed greater accuracy than either the Lewis or pre vious Harman ct al. equations and underestimated peak power by less than 1% , with a SEE of 355.0 W using SJ protocol. The use of one equation for both males and females resulted in only a slight (5% of power output) differenc e between genders. Using CMJ data in the SJ-derived equation resulted in on ly a 2.7% overestimation of peak power. Cross-validation of regression equa tions using PRESS reveals accurate and reliable R-2 and SEE values. Conclus ions: The SJ equation is a slightly more accurate equation than that derive d from CMJ data. This equation should be used in the determination of peak power in place of the formulas developed by both Harman et al, and Lewis. S eparate equations for males and females are unnecessary.