摘要：The influence of cooling on lower limb muscles was measured by excitability of motor neuron pool in level of spinal cord as the Hoffmann reflex(H-reflex) response. Although current researches have discussed about the recruitment threshold of motor units(MUs) activity, the changing of cutaneous temperature by cooling has not been examined. This study analyzed 1) the change in the excitation of the motor neuron pool, which was indicated by the amplitude of the Hoffmann reflex measured for muscles of the leg when the skin temperature was lowered , and 2) the manner in which afferent nerve inputs were integrated in the motor neuron pool. The subjects were seven healthy males without a previous history of neural diseases. The distribution of skin temperature in the leg was obtained thermographically, and the amplitude of the Hoffmann reflex of the soleus muscle was measured using a pair of Ag-AgCl electrodes(diameter=8mm) which were attached to the skin surface at the midline of the back of the calf; the skin temperature was subsequently lowered from 33.1°C to 22°C. The motor neuron pool exhibited maximum excitability when the skin temperature was 26 °C; at this time the amplitude was approximately 43% greater than when the skin temperature was 33.1 °C(control : without cooling condition). The excitability of the motor neuron pool decreased steadily at skin temperature above and below 26 °C, and was at a minimum when the skin temperature was 22 °C. The present study showed that the amplitude of the Hoffmann reflex was significally affected by the lowering of the skin temperature.
