As volleyball players are exposed to high volumes of forceful jump-landing actions, the risk of injuries is increased. Wearable technology such as the VERT device offers a promising avenue for load monitoring of volleyball players, potentially allowing better control of intensity of training and matches to minimize the likelihood of injuries. Although validity of jump counts and jump height is well investigated, studies validating impact forces estimated by VERT device referenced to force plate data are scarce. The objective of this study was to validate the use of VERT for the estimation of impact forces during volleyball. Twenty-one volleyball players of different levels performed countermovement jumps (CMJ), block jumps, spike jumps, and a set with a combination of several volleyball jump-landing tasks. Impact forces estimated by VERT were compared with resultant force values measured using a force plate. A total of 221 spike jumps, 286 block jumps, and 203 CMJ were analyzed. Given the identified proportional bias and heteroscedasticity, an adapted Bland-Altman plot featuring the line of best fit and V-shaped 95% confidence intervals instead of classic limits of agreement was created. Furthermore, our results suggest a proportional bias between the 2 measurements, with the VERT sensor tending to overestimate impact forces compared with the force plate, increasingly at higher mean values. Therefore, the VERT algorithm has not been proven valid for quantifying impact forces. However, a correction factor is proposed to obtain better results for impact forces estimated by VERT, making it suitable for implementation in sport contexts.
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