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Abstract
The aim of this study was to assess the mechanical differences calculated from hip acceleration (accelerometer attached to the hip), bar acceleration (accelerometer attached to barbell) and centre-of-mass acceleration (force plate) during vertical countermovement jumps (CMJs) and the reliability of each system. Eighteen elite male rugby players served as participants. In relation to the force plate, the bar accelerometer revealed similar peak velocity (PV [2%]) and peak power (PP [2%]), but predicted greater peak force (PF [24%]) during the concentric phase, whereas the hip accelerometer predicted similar PF (2%) but underpredicted PV (21%) and PP (24%) during the concentric phase. Both accelerometer attachments were deemed reliable for assessing PF (correlation coefficient, ICC = 0.80–0.83 and standard error of measurement, SEM = 3–13%), but were low/moderately reliable for monitoring PV and PP (ICC = 0.35–0.77 and SEM = 11–23%). The eccentric phase variables were unreliable across all devices and attachment sites. The kinematics and kinetics measured by the three systems (hip accelerometer, bar accelerometer and force plate) varied significantly (p < 0.05). Based on the outcomes, it is recommended that the force plate be used as the primary means of assessing CMJ performance until the stability of wireless accelerometry set-ups and protocols are improved.