抄録
The present investigation attempted to clarify whether intensity of exercise influences functional sympatholysis during mild rhythmic handgrip exercise (RHG). In eleven subjects, we measured muscle oxygenation both exercising and non-exercising muscle in the same arm by near infrared spectroscopy (NIRS), heart rate and blood pressure. We obtained the total labile signal to assess a relative evaluation for muscle oxygenation by occlusion for 6 minutes at rest. Subjects performed RHG (20 times / minute) for 6 minutes at 10%, 20%, and 30% of maximal voluntary contraction (MVC) at random. We used nonhypotensive LBNP of -20 mmHg for 2 minutes to elicit muscle sympathetic nerve activity at rest and during RHG. LBNP caused a decrease of 16.4% (pre), 18.6% (post), respectively, in oxygenation at rest. The attenuation of decrease in oxygenation in non-exercising muscle to LBNP during RHG did not elicit. On the other hand, the decrease in oxygenation in exercising muscle attenuated progressively as exercise intensity increased, when LBNP was applied during exercise. The attenuation of decrease in oxygenation to LBNP during RHG at 20% and 30% exhibited differences from the rest (p<0.05). These findings indicate that an increase in the intensity of exercise cause functional sympatholysis during mild RHG. [Jpn J Physiol 54 Suppl:S252 (2004)]
