Acute leg-cycling exercise attenuates the H-reflex recorded in soleus but not flexor carpi radialis.
The amplitude of the Hoffman reflex (H-reflex) in the soleus muscle is attenuated after acute bouts of leg-cycling exercise. The attenuation has been interpreted as a "tranquilizing" effect of exercise controlled by the central nervous system and generalized beyond a single spinal segmental level. If so, the postexercise depression of the H-reflex should occur in both the soleus and the flexor carpi radialis (FCR) muscle, which is not actively involved during leg cycling. This experiment examined the effect of moderate-intensity cycling exercise on the H-reflex recorded in soleus and FCR among 16 men. The H-reflex was measured immediately before and 10 min after 30 min of either moderate-intensity leg cycling (60% VO(2peak)) or quiet rest. The acute bout of cycling exercise reduced the H-reflex in the soleus but not in the FCR. Thus, the attenuation of the H-reflex after leg cycling does not generalize beyond the spinal segmental level that modulates the involved locomotory muscles; it is likely the result of segmental processes associated with the repetitive stretching or activation of the soleus muscle.
Motl
Robert W
RW
Department of Exercise Science, The University of Georgia, Ramsey Student Center, 300 River Road, Athens, Georgia 30602-6554, USA. rmotl@coe.uga.edu
Dishman
Rod K
RK
D000328:Adult; D000704:Analysis of Variance; D001132:Arm / Q000502:physiology*; D005080:Exercise Test / Q000379:methods*; D006181:H-Reflex / Q000502:physiology*; D006801:Humans; D007866:Leg / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*