Abstract

Force and power are key exercise outputs in research and training practice. The direct acquisition of this kinetic data typically requires a force plate, which is not always practical and cost-effective, and generally limited to laboratory-based settings. Thus, kinematic systems (eg, linear position transducers, accelerometers) are becoming increasingly popular as tools for calculating force and power in situ during exercise. The aim was to assess the validity of a commercial linear position transducer and accelerometer for calculating force and power during squat jumps. Seven healthy males performed 2×single repetition squat jumps with four loads (20 kg, 40 kg, 60 kg and 80 kg). The squats were performed on top of a Kistler force plate. A commercial linear position transducer (Gymaware (GYM)) and accelerometer (Myotest (MYO)) were attached to the bar to assess concentric peak force (PF) and peak power (PP), based on the combined mass of the external load and each subject. Data were pooled across all loads for analysis. The PF and PP data from the GYM and MYO systems were strongly correlated with the force plate data (r=0.84-0.93, p<0.001) and also with each other (r=0.90-0.97, p<0.001). The mean PF and/or PP values calculated from the GYM and MYO systems were found to be 4.5%-6.5% higher than the measured values from the force plate (p<0.01). The PF and PP data from the linear position transducer and accelerometer showed strong relative validity compared to the force plate, but some differences in absolute validity were noted. The two kinematic systems provide other benefits (eg, portability, ease of use, cost effectiveness) for assessing PF and PP during squat jumps or similar isoinertial exercises.