## 3 Results
### Main Results of the Included Studies  
Of the nine studies included in the review, 77.7% focused on the assessment of jumping height using the VERT device (\(n=5\)) [8; 17; 18; 21; 24], Blast Athletic (\(n=1\)) [19], and GPSports (\(n=1\)) [23] (Table 3). ### Main Results of the Included Studies  
Of the nine studies included in the review, 77.7% focused on the assessment of jumping height using the VERT device (\(n=5\)) [8; 17; 18; 21; 24], Blast Athletic (\(n=1\)) [19], and GPSports (\(n=1\)) [23] (Table 3). \begin{table}
\begin{tabular}{c c c} \hline
**References** & **Main Aim** & **Main Findings** \\ \hline \multirow{4}{*}{[PERSON] et al. [17]} & To evaluate the validity of a commercially & \multirow{4}{*}{Jump height} \\  & available wearable device, the Vert, for measuring & \\  & vertical displacement and jump count in & & \\  & volleyball athletes. & & \\ \hline \multirow{4}{*}{[PERSON] et al. [18]} & To validate the use of an inertial measurement unit & \multirow{4}{*}{SVJ: r = 0.67, 9.2 cm} \\  & (IMU) to collect total jump count and assess the & & \\  & validity of an IMU for the measurement of jump & & \\  & height against 3-D motion analysis. & & \\  & & & \\  & & & \\ \hline \multirow{4}{*}{[PERSON] and [PERSON] [19]} & To validate the Blast Athletic Performance monitor & \multirow{4}{*}{SVJ: r = 0.67, 9.2 cm} \\  & to assess vertical jump in collegiate volleyball & & \\  & athletes and to determine the Blast’s utility for & & \\  & tracking change in jump height across a & & 19.8–21.0\% \\  & volleyball season. & & \\ \hline \multirow{4}{*}{[PERSON] et al. [20]} & To assess the skill levels of volleyball spikers with & \multirow{4}{*}{AA: 94\%} \\  & a wearable sensing device (WSD) based on MEMS & & \\  & motion sensors. & & \\ \hline \multirow{4}{*}{[PERSON] et al. [21]} & To evaluate the validity and reliability of this & \multirow{4}{*}{Reliability (inter-device): r = 0.99, 95\% CI 0.98 to} \\  & device, the Vert, to count jumps and measure jump & & \\  & height with professional volleyball players. & & \\ \hline \multirow{2}{*}{[PERSON] et al. [8]} & To examine the accuracy of Vert landing impact & \multirow{2}{*}{PA (limits of agreement): \(-\)84.13\% and 52.37\%} \\  & values in university volleyball players. & & \\ \hline \end{tabular}
\end{table} 
Table 3: Analysis of the main results of the studies included in the review. Figure 3: Risk-of-bias items are presented as percentages across all included studies. [PERSON] et al. (2017) and [PERSON] et al. (2011) reported a high correlation (r = 0.83-0.99) with other devices in jump height. In the study by [PERSON] and [PERSON] (2019), there was a moderate-high correlation between the standing vertical jump (r = 0.67) and the one-step vertical jump (r = 0.69). [PERSON] et al. (2018) found improvements in maximal and submaximal height jumps of 1.3-3.8% and 3.1-5.1%, respectively. [PERSON] et al. (2014) found a coefficient of variation in jump height in the attack zone of 7.8% and 7.9% during the block. [PERSON] et al. (2018) reported a peak acceleration at the limits of agreement in jump height of \(-\)84.13% and 52.37%. Finally, [PERSON] et al. (2013) reported 1201 video jumps during a training session. Of the 1201 jumps, it was found that 1144 (95%) of the jumps on the inertial data were performed correctly, 57 (5%) of the jumps were considered false negatives, and 54 (4%) false positives. It was also possible to verify that the flight time in the jumps was \(-\)0.015 \(\pm\) 0.058 s.  
The remaining 25% of the studies (\(n=2\)) were based on other devices to assess the performance of volleyball players (20; 22) (Table 3). [PERSON] et al. (2012) highlighted, at the balanced level, an average unweighted recall (UAR) in the gyroscope and the barometer for the non-dominant hand (NDH) of 74.71% and 52.72%, respectively.