Concurrent validity of the portable gFlight system compared to a force plate to measure jump performance variables

Objective. Lower-limb strength and power is commonly assessed indirectly by measuring jump performance. A novel portable system (gFlight) that can be used in applied settings provides measures of jump performance. The aim of this study was to validate jump performance measures provided by the gFlight to those provided by a force plate. Approach. Thirty-six participants performed three countermovement jump (CMJ) and drop jump (DJ) trials. Jump height (JH), contact time, and reactive strength index (RSI) were simultaneously recorded by a force plate and gFlight sensors to assess concurrent validity. Main results. The gFlight provided significantly higher measures of JH during the CMJ (mean: +8.79 4.16 cm, 95% CI: +7.68 to 9.90 cm, P < 0.001) and DJ (mean: +4.68 3.57 cm, 95% CI: +3.73 to 5.63 cm, P < 0.001) compared to the force plate. The gFlight sensors displayed significantly higher measures of RSI (mean: +0.48 0.39 ms(-1), 95% CI: +0.37 to 0.58 ms(-1), P < 0.001) and lower measures of contact time (mean: -0.036 0.028 s, 95% CI: -0.044 to -0.029 s, P < 0.001) during the DJ compared to the force plate. The bias displayed by the gFlight for JH, contact time and RSI measures are reduced using corrective equations. Significance. The gFlight sensors are a cost-effective, portable measurement system with high concurrent and ecological validity for the objective measurement of jump performance in applied settings. Corrective equations should be used to reduce measurement biases so comparisons can be made to force plate measurements of jump performance.

Automated summary

The study found that the gFlight system provided higher measures of jump performance compared to the force plate, especially in assessing reactive strength during drop jumps. The use of corrective equations can help reduce measurement biases displayed by the gFlight system.