Isokinetic testing of muscle performance: New concepts for strength assessment

BACKGROUND: Peak torque (PT) is considered the most representative parameter of muscle performance in isokinetic dynamometry while other computable parameters such as mean peak torque (MPT), maximal work (maxW) and mean work (meanW) are generally neglected. OBJECTIVES: This cross-sectional study reassessed whether PT is the only necessary parameter in isokinetic testing and weighed the contribution of each variable to muscle performance. METHODS: Thirty apparently healthy volunteers underwent isokinetic assessment of the ankle dorsiflexors of both legs at 45 and 90◦/s. Bivariate relationships and multivariate associations between PT,MPT, maxW and meanW were examined employing Pearson’s analysis and principal component analysis (PCA), respectively. RESULTS: At both velocities, Pearson’s coefficients were very high between PT and MPT as well as between maxW and meanW (r > 0.9; p < 0.0001) and fair-to-good (r = 0.65–0.73; p < 0.0001) between torque and work measures. At 90◦/s the PT and MPT mostly contributed to muscle performance while at 45◦/s, MPT and meanW exhibited the highest component loadings, whereas PT performed poorly. CONCLUSIONS: Isokinetic variables contributed with different loadings to muscle performance of ankle dorsiflexors, depending on the angular velocity employed. In particular, work measures may usefully complement the conventional PT-only analysis, especially in rehabilitative settings where low speeds are recommended.