Force overestimation during tourniquet-induced transient occlusion of the brachial artery and possible underlying neural mechanisms.

A vascular occlusion by a tourniquet inflated at the proximal end of the upper arm is suggested to affect the estimation of exertion force level. In the first part of this study, subjects were asked to estimate the isometric force exerted by the occluded hand with that of the other hand (matching experiment). We found that the perceived force with arterial occlusion was always overestimated. To examine the underlying neural mechanism for this phenomenon, in the second part, the somatosensory evoked potentials (SEPs) and nerve action potential (NAP) were recorded following electrical median nerve stimulation with or without arterial occlusion. Moreover, the maximum motor response (M response) to median nerve stimuli at the axilla was recorded from the skin surface of the thenar eminence muscle of the hand during with arterial occlusion. The N20 of SEP and NAP at Erb's point were unaffected by the arterial occlusion, and the M response was also unchanged. These results suggest that the tourniquet-induced transient occlusion of the brachial artery does not seriously affect median nerve function. Thus, it is likely that the primary responsible factor for the overestimation of perceived force exertion during arterial occlusion is the centrally generated motor command as previously hypothesized by McCloskey [McCloskey, D.I., Ebeling, P., Goodwin, G.M., 1974. Estimation of weights and tensions and apparent involvement of a "sense of effort". Exp Neurol. 42, 220-232; McCloskey, D.I., 1978. Kinesthetic sensibility. Physiol. Rev. 58, 763-820; McCloskey, D.I., 1981. Corollary discharge and motor commands and perception. In: Brookhart, J.M., Mountcastle, V.B. (Eds.), Handbook of Physiology. American Physiological Society, Bethesda, pp. 1415-1447].