Effects of a specific ecutaneous cold stimulus on single motor unit activity of medial gastrocnemium muscle in man.
The effect of a specific skin cooling stimulus on single motor unit (SMU) activity in the underlying medial gastrocnemius muscle on forty normal subjects was examined by computer analysis of the real time occurrence of each unit during a 12 minute experiment. Subjects (N, 17) discharging SMUs at a comfortable resting frequency (5.2 +/- 0.9 Hz) showed a tendency toward inhibitory responses during the first minute of cooling. Most subjects (13 of 18) who discharged SMUs at a frequency of 0.5 Hz underwent a statistically significant increase in SMU activity during the first minute and then a significant reduction in activity during the next minute of cooling. The general findings suggest that motor outflow can be altered in muscle underlying a specific thermal stimulus and that the central excitatory state of the nervous system plays a large role in determining how cutaneous cooling information will be processed to affect motor changes.
D003080:Cold Temperature; D003201:Computers; D006801:Humans; D007866:Leg; D009046:Motor Neurons / Q000502:physiology*; D009132:Muscles / Q000502:physiology*; D012867:Skin