INFLUENCE OF COLD SHIVERING ON FINE MOTOR CONTROL IN THE UPPER-LIMB

The aim of the investigation was to determine the effects of cold shiv ering on the accuracy of force output in distal, middle and proximal m uscles of the upper limb. Tests of hand grip strength, elbow flexion a nd shoulder flexion leach done at 10% maximal voluntary contraction fo r 15 s) were done under three conditions: (1) thermoneutral air (27 de grees C), a condition of thermal comfort; (2) cold air (10 degrees C), a condition eliciting an increase in tonic muscle activity, (3) and c old air (10 degrees C) with a cold drink 18 degrees C), a condition th at causes visible shivering. The averaged (root mean square) electromy ogram (AEMG) and mean power frequency (MPF) were measured from proxima l, middle and distal arm muscles during the tests and compared. The co ntrol of force output was highly effective at thermoneutral condition for all motor tasks. During the cold air condition, all muscles were t onically active but there was no effect on accuracy of test performanc e. However, AEMG increased approximate to 20% (P < 0.05) with respect to test performance in thermoneutral condition. During the cold air/co ld drink condition, all muscles were shivering to a different extend. AEMG during test performance increased 30-150% in comparison to thermo neutral condition (P < 0.05). In this case, hand grip and elbow flexio n were not adversely affected (these tests require middle and distal m uscles) by cold shivering. However, the accuracy of performance of sho ulder flexion was adversely affected. This is consistent with the fact that proximal muscles are more active during cold shivering.