Reliability and Validity of the Jumpster accelerometer-based app compared to the Vertec when completing a countermovement jump

The reliability and validity of the Jumpster app (JA) was compared to the Vertec. Thirty-six participants completed 100 total trials using both tools simultaneously. Validity was assessed using correlation and tolerance analyses. Reliability was assessed using 95% predictive intervals (PI95) and tolerance limits (TL95) between the measures, comparing standard error of the measure (SEM) and coefficients of variation (CV) for each tool, and examining the intraclass correlation coefficient (ICC 2,K; upper and lower 95% CI) comparing both tools. The JA was weakly related to the Vertec (r = 0.24; p < 0.01). The tolerance analysis showed a moderately strong proportional bias of the JA (r = 0.45; p < 0.01). While all data fell within calculated PI95 ±TL95, the JA SEM (14.7cm) and CV (40.30%) exceeded the Vertec SEM (3.57cm) and CV (7.22%) with an ICC of 0.55 [0.79, -0.08]. These JA is neither reliable or valid.