A model of "sense of effort" during maximal and submaximal contractions of the tongue.

Fatigue in the oral motor system may be accompanied by the perception of an increased "sense of effort." Awareness of centrally generated motor commands that result in synaptic inputs to motoneuron pools are thought to be responsible for these perceptions of effort (e.g., Muller, 1840; McCloskey, 1981). Few studies of the perceptual phenomenon of sense of effort exist, particularly of the oral motor system. The present study required 20 normal adults to push on a fluid-filled bulb using their tongue and hand. Subjects repeatedly exerted from 10 to 100% of the maximal effort, in random order, in 10% increments. The pressure produced by pushing on fluid-filled bulbs was compared to the effort level attempted. Subjects produced consistent, reliable pressures related to effort level. The best mathematical model for both the tongue and hand data was third-order polynomial. It is hypothesized that the perception of effort derives from a central source that operates across various motor systems.