A Novel Method to Reduce the Impact of Countermovement Jump Monitoring In Professional Rugby Athletes

Abstract

The countermovement jump (CMJ) is widely used to monitor jump performance, with greater interest being demonstrated in the propulsive phase. When landing from a CMJ, high forces are produced; this can increase the risk of injury. The present study aimed to test the validity and reliability of a countermovement jump to a box (CMBJ) where the forces associated with the landing are reduced. Eighteen professional rugby athletes (age=22 ± 2 years; body mass=104.2 ± 13.0 kg; height=187.4 ± 7.1 cm) performed 3 CMJ’s and 3 CMBJ’s on 3 different occasions. Net impulse (N.s), peak and mean absolute and relative force (N; N/kg) were obtained from a force plate system. The kinetic validity of the CMBJ was assessed by calculating the intraclass correlation coefficient, Pearson product-moment correlation, Cohen’s effect sizes and statistical hypothesis testing (paired t-test) in comparison to the CMJ. Intraday and interday reliability was assessed for each variable for both jumping conditions by calculating typical error, within subject coefficient of variation and intraclass correlation coefficient. Nonsignificant, trivial differences between the CMJ and CMBJ were observed for all jump variables. Low within-subject variability was observed between the CMJ and CMBJ for all variables. Interday and intraday variability showed good reliability and an almost perfect interday agreement score. In conclusion, net impulse, peak and mean force and relative peak and mean force obtained from a CMBJ are valid and reliable to monitor jump performance. This data demonstrates that the CMBJ is a viable alternative to monitor jump performance in athletes.