We hypothesize that the relationship between muscle cellular pH for input signal of muscle metaboreflex and mean arterial pressure (MAP) for output signal of the reflex could be linear fashion and express the characteristics of muscle metaboreflex in humans. Thus, first purpose of this study was to examine the above hypothesis in human subjects. Second, we examined whether the above relationship would be changed by exercise training. Subjects were 7 normal male volunteers for control group and 4 male tennis players for training group.
　We measured muscle cellular pH thorough phosphorous nuclear magnetic resonance spectroscopy (³¹P-NMR), MAP and heart rate (HR) during ischemia after sustained handgrip exercise at 50% of maximum voluntary contraction (MVC). Contraction was sustained for 30, 45, and 60 s, followed by 2 min of circulatory arrest, respectively. Muscle cellular pH during the ischemia decreased linearly with increasing contraction time after 30, 45, and 60 s contractions. The MAP did not change during the ischemia after 30 s contractions. However, it significantly increased after 45 and 60 s contractions. The linear relationship between MAP and pH was seen in all of subjects and each regression coefficient was above 0.80.
　This indicates that the slope of relationship between muscle cellular pH and MAP can be calculated in individual to evaluate the gain of muscle metaboreflex by the method of this study. The slope which was calculated from all of data in control group was not significantly different from that in training group. This suggests that the gain of muscle metaboreflex would not be changed by daily tennis training.

DESCENTE SPORTS SCIENCE Vol.16/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE