None are Accurate but Some are Useful: A Comparison of Different Systems Used to Assess Jump Height in Volleyball

Training load monitoring and performance testing are crucial components within high-performance sports. In volleyball, jump height both contributes to the training load and is an important performance measure to monitor. In practice, various different measurement systems, each with their own methods of estimation, are used. Therefore, the aim of this study is to compare the accuracy of different approaches in order to provide a “best practice” suggestion. To answer this research question, sixteen elite male volleyball players (16-18 years) completed several jumps for seven different (sport-specific) jump types. The jumps were measured with the following systems: three direct flight time (FT) based systems (force plate, high-speed camera, and Optojump), two wearable inertial measurement units (IMUs; Vert and Kinexon), two take-off velocity (TOV) based systems (force plate and high-speed camera), and two direct displacement systems (high speed camera and Yardstick). Validity was examined with the (standardized) typical error of the estimate and Bland Altman statistics with Optojump as the Benchmark system. The results show that FP FT, Kinexon, Vert and Yardstick can be use almost interchangeable showing trivial or small differences in sTEE (.10- 0.35). In contrast Video TOV, FP TOV and Video disp were less accurate with medium to large sTEE differences (0.66-1.31). In practice, care should be taken when different measurement systems are used alongside one another given different degrees of agreement between different measurement systems.