Force-velocity relations in human skeletal muscle.

Based on the physiological principles of the muscular force-velocity concept, this paper deals with the special problems associated with determining and interpreting force-velocity relations of muscles in situ particularly in humans. In the strict sense, instead of force-velocity relations merely torque-angular velocity relations of a joint can be measured directly under in situ conditions. This calls for biomechanical model calculations to obtain force-velocity relations of single muscles involved in joint motions. In addition to discussing these basic principles, the methodological problems arising in measurements with so-called isokinetic dynamometers are also explicitly described. An important message of this paper is to sensitize potential users of this method to these problems as the isokinetic dynamometry has more or less become standard procedure worldwide. The possibility of the characterization of muscle fiber composition and the evaluation of power on the basis of human muscle force-velocity relations is also discussed. A final section considers the effects of muscle training on the torque-angular velocity relations. The contents of this paper can be understood as a guide to avoid obtaining conflicting results when measuring human torque-velocity relations.