Estimation of peak muscle power from a countermovement vertical jump in children and adolescents
Several equations to predict muscle power (MP) from vertical jump height (VJH) have been developed in adults. However, few have been derived in children. We therefore aimed to: 1) evaluate the validity of existing MP estimation equations from a vertical countermovement jump (CMJ) in children and adolescents, and 2) develop and validate a new MP estimation equation for use in children and adolescents. We measured peak MP (Watts) and VJH (cm) during a CMJ using a force platform in 249 children and adolescents (9-17 years; 119 boys). We compared actual (force platform) to predicted (twelve existing prediction equations) MP using repeated measures ANOVA and estimated bias using modified Bland-Altman plots. We developed a new prediction equation using stepwise linear regression, assessed predictive error using leave-one-out and ten-fold cross-validation and externally validated the equation in an independent sample (n=100). All existing prediction equations demonstrated some degree of bias, either systematic bias (mean differences ranging 178 W to 1377 W; 8%-64%), bias at the extremes or interactions with sex. Our new prediction equation estimates MP from VJH and body mass: Power (W) = 54.2*VJH(cm) + 34.4*body mass(kg) – 1520.4. With this new equation, there was no difference between actual and predicted MP (0%) and negligible differences (0.2-0.9%) in R2 and root mean square error between our observed and cross-validated sets. Actual and predicted MP were not different in our external validation (p=0.12). The new equation demonstrates excellent validity and can be used to predict MP from a CMJ in children and adolescents.