Maximum velocity during loaded countermovement jumps obtained with an accelerometer, linear encoder and force platform: A comparison of technologies.

The maximum velocity (Vmax) reached during countermovement jumps (CMJ) has been considered a performance indicator to evaluate vertical jump ability. The aim of this study was to compare Vmax during loaded CMJ (CMJloaded) using three different technologies to show a criterion for selecting the more appropriate depending on its use. Nine recreationally active men performed a CMJloaded test. Five jumps were made in each of 6 series with a 20- kg barbell + 0, + 5, + 10, + 15, + 20 and + 25 kg, with 2 seconds rest between the jumps and 5 minutes rest between the series to explore a wide range of speeds. Vmax was obtained from force platform, inertial device and linear encoder technologies. Bland-Altman plots and mean differences were used to compare devices. Reproducibility was tested using the intraclass correlation coefficient (ICC) for single measures and typical error (TE). All technologies showed high levels of reproducibility, ICC higher than 0.75 and TE lower than 10 %. There were non-significant differences in Vmax between each pair of technologies (linear encoder 2.11 ± 0.24 m·s-1, accelerometer 2.11 ± 0.26 m·s-1, force platform 2.12 ± 0.24 m·s-1) reporting a very low bias. However the limits of agreement between the different technologies evaluated were high (± 0.33 m·s-1). In conclusion, the accelerometer, linear encoder and force platform were suitably reliable to be used to measure Vmax during loaded vertical jumps but their values were not interchangeable.