The senses of effort and force during fatiguing contractions

The sensory basis upon which judgments of force are made during fatiguing isometric contractions is reviewed. At issue is whether the perception of force is based on centrally generated sensations arising from the motor command, known as the sense of effort, or from peripheral sensations originating in the muscle, and termed a sense of force. The results from a number of studies indicate during sustained constant-force contractions the perceived magnitude of the force increases, which is consistent with the idea that judgments of force are based on centrally generated signals. It is, however, possible for some subjects to dissociate effort and force and to make accurate judgments of the magnitude of forces during fatigue.