Effect of cooling on force oscillations during maximal voluntary eccentric exercise.
The effect of superficial cooling on force oscillations during maximal eccentric exercises of the quadriceps femoris was studied in 10 adults. Maximal (i) shortening (concentric) and (ii) lengthening (eccentric) exercises were performed at a velocity of 120 degrees/s through 60 degrees of knee flexion while linear envelope EMG signals were recorded from the surface of the vastus medialis muscle. Force oscillations (12.4 +/- 2.8 Hz) were present in all subjects in the first series of eccentric exercises. After 30 min of cooling, the oscillations were eliminated in two subjects and were reduced in number in two others of the five subjects in the experimental group. In contrast, all subjects in the control group still had oscillations when retested after a 30-min rest period. During the eccentric exercises, a synchronous silent period in the EMG tracings was evident just before a decrease in force. Subsequently, the EMG activity resumed and the force increased (force oscillation). Because the force oscillations were of large amplitude and occurred only during eccentric exercise, we conclude that the force oscillations were similar to physiological action tremor. Because the force oscillations and EMG patterns were altered by cooling, the mechanisms that initiate such oscillations during maximal eccentric exercise are suspected to include a neural component.
D003080:Cold Temperature; D004576:Electromyography; D006801:Humans; D007866:Leg; D009119:Muscle Contraction