Reliability and Validity of the Jumpster Accelerometer-Based App Compared to the Vertec When Completing a Countermovement Jump: An Examination of Field-Accessible Tools

The reliability and validity of the Jumpster app was assessed via a comparison to the Vertec during a countermovement jump. Using both tools simultaneously, 36 participants completed 100 total jump trials. Validity was assessed using correlation and tolerance analyses. Reliability was assessed using 95% predictive intervals (PI95) and tolerance limits (TL95) between the measures, comparing the standard error of the measure (SEM) and coefficients of variation (CVs) for each tool and by examining the intraclass correlation coefficient (ICC 2,K; upper and lower 95% CI) comparing both tools. The Jumpster app was weakly related to the Vertec (r = 0.24; p < 0.01). The tolerance analysis showed a moderately strong proportional bias of the Jumpster app to the Vertec (r = 0.45; p < 0.01). While all data fell within the calculated PI95 ± TL95, the Jumpster app SEM (14.7 cm) and CV (40.30%) exceeded the Vertec SEM (3.57 cm) and CV (7.22%), and the ICC was 0.55 [0.79, −0.08]. These results paired with an overall app failure rate of 15.97% indicate that the Jumpster app is neither reliable nor valid for measuring the countermovement jump.