A principal component analysis of sport-specific isometric evaluation

The purpose of the study was to identify the sport-specific range of joint angles for the knee extensors' muscular strength during isometric evaluation. Twenty young female track and field jumpers (J) and 21 volleyball players (V), aged 13-19 years, participated in the study. The values of torque at the initial 200 ms (T-INIT) and of maximum torque (T-MAX) were determined from the torque-time curve at each knee angle. A 2 (Group) x 9 (Angle) ANOVA was applied to examine the between group differences of T-INIT and T-MAX. Principal component analysis (PCA) followed by varimax rotation was performed to investigate the angle sport-specificity of T-INIT and T-MAX. Track and field jumpers demonstrated higher torque values, however, these values did not yield statistical significance at all knee angles (p > 0.05), either for T-INIT or T-MAX - PCAs revealed an angle sport-specific loading of T-INIT and T-MAX, which were heavier loaded on the first component at the angles closer to full knee extension and at the angles closer to knee flexion, in the track and field jumpers and the volleyball players, respectively. These findings provide evidence for the knee angles to be included in a more specialized sport-specific isometric evaluation.