Isokinetic eccentric exercise.

Abstract

The development of active isokinetic dynamometers has allowed the assessment of muscular moment under eccentric activations that have different characteristics to concentric actions. It is well documented that at a given angular velocity the eccentric moment is greater than the corresponding concentric moment. The moment-velocity relationship under eccentric conditions has been investigated, with conflicting results. Particularly, eccentric moment was reported to remain similar to, or to increase or decrease with, increasing angular velocity. As with concentric actions, the reliability of isokinetic eccentric measurements is influenced by a number of factors such as gravity, preload force and testing position. The velocity-specific effects of eccentric training have not been extensively investigated. Based on current knowledge, eccentric exercise does not appear to be velocity-specific. Although the mode specificity of both concentric and eccentric exercises have been investigated, the resultant observations are conflicting. Eccentric training has been found to improve both concentric and eccentric strength: yet, it has also been reported to improve only concentric or eccentric strength. The reciprocal muscle group ratios under eccentric actions were found not to be influenced by angular velocity, but the significant role of the eccentric/concentric moment ratio of each muscle has not been examined thoroughly. It is well documented that eccentric activations are associated with delayed muscle soreness and muscle damage. A limited number of studies have reported that isokinetic eccentric efforts may result in a lower amount of muscle soreness compared with other exercise modalities. Isokinetic dynamometers provide some unique characteristics for rehabilitation applications. Examination of the clinical application of eccentric exercise is limited. Consequently, the use of this exercise modality in prevention and assessment of musculoskeletal injuries should be investigated further.