Validity and reliability of a kinematic device for measuring the force developed during squatting

This study determined the validity and reliability of the kinematic device developed by Bosco et al. (1995) by comparing its peak force, peak velocity, and peak Fewer measurements to data obtained simultaneously with a force platform placed under the subject's feet. Fifteen international downhill skiers performed maximal half-squats on a guided barbell with masses of 60-180 kg. The coefficient of correlation (r) between the two peak forces (r = 0.85-0.95, p <.001), the two peak velocities (r = 0.74-0.91, p <.001), and the two peak powers (r = 0.85-0.95, p <.001) indicated that the kinematic device measurements were valid. The trial-to-trial reliability of half-squat exercises measured by the kinematic device gave an intraclass coefficient of correlation (CR) of: 0.7-0.90 for peak force, 0.62-0.90 for peak velocity, and 0.57-0.91 for peak power. There were no statistical differences between the two trials. The standard error of the means (SEM%) was less than 5% for peak farce, less than 4% for peak velocity, and less than 7% for power. The high CR and low SEM% indicate that the kinematic device is reliable. The movement recorded by the kinematic device accurately described the action measured by the force platform.