Analysis of Movement Variability During the Spike Jump Action in Young and High-Level Female Volleyball Players: Differences Between Categories and Playing Positions

<b>Objectives</b>: The aim of this study was to analyze and compare movement variability (MV) during the spike jump (S) action with and without a ball in volleyball players of different categories and playing positions. <b>Methods</b>: A total of 48 volleyball players participated in this study. The players were divided according to the following categories: under-14 (U-14) (n = 12); U-16 (n = 12); U-19 (n = 12); and SENIOR (n = 12). Also, they were divided according to playing position: hitters (n = 24); liberos (n = 5); middle blockers (n = 12); and setters (n = 7). The S action with and without a ball was analyzed. Acceleration was analyzed using an IMU device. Acceleration was used to calculate MV through sample entropy (SampEn). <b>Results</b>: Differences were observed in all categories when comparing the S action with and without the ball (<i>p</i> < 0.001). SampEn was higher in the U-14 category (<i>p</i> < 0.001). Regarding playing positions, SampEn was lower in the hitter position compared to the middle blocker (<i>p</i> < 0.001) and libero (<i>p</i> < 0.001). There were significant inverse correlations between years of experience and SampEn (<i>p</i> < 0.05). <b>Conclusions</b>: The inclusion of a ball during the S action increases MV. MV is higher in the U-14 category compared to the rest. The hitter position showed lower MV compared to the other playing positions.