Objective: The purpose of this study was to investigate the changes in blood circulation of tendons and heart rate variability (HRV) during and after acupuncture in order to elucidate the mechanisms of acupunctureinduced changes in tendon blood circulation. Materials and Methods: During 10 minutes of acupuncture treatment and a recovery period of 40 minutes, blood volume (THb) and oxygen saturation (StO 2) of treated and nontreated tendons were measured using red laser lights. In addition, HRV was also measured during the experimental period. Results: THb and StO 2 of the treated tendons significantly increased during acupuncture, and then remained high during the recovery period. THb and StO 2 of the nontreated tendons did not change during acupuncture but gradually increased during the recovery period. In addition, the increase in THb of the nontreated tendons were significantly correlated with that of the treated tendons during the latter half of the recovery period. Heart rate (HR) continued to decrease during acupuncture and suddenly returned to the initial level after removal of the needle. The low-frequency (LF)/high-frequency (HF) ratio tended to increase during the recovery period. During the latter half of the recovery period, the changes in THb for both the treated and nontreated tendons were negatively correlated with the change in HR but not with changes in the LF/HF ratio. Conclusions: These results suggest that changes in blood circulation of tendons after acupuncture treatment were controlled by the autonomic nervous system, which could not be detected by HRV analysis.

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The purpose of the present study was to examine acute changes in active muscle stiffness with and without the stretch reflex following static stretching. Before and after static stretching for 10 min, active muscle stiffness was measured according to changes in exerted torque and fascicle length during short-range stretch of faster (peak angular velocity of 250 deg•s-1 ; without the stretch reflex) and slower (peak angular velocity of 100 deg•s-1 ; with the stretch reflex) angular velocities. During the measurement of active muscle stiffness, the electromyographic activities of plantar flexor muscles were recorded and averaged over two different phases: just before (mEMGa) and after (mEMGb) stretch. In addition, the mEMGb/ mEMGa ratio was used to evaluate the effects of stretch reflex. After 10 min of stretching, the mEMGb/mEMGa ratio tended to decrease under the 100 deg•s-1 condition, but not 250 deg•s-1. Under both conditions, active muscle stiffness did not change after 10 min of static stretching. In conclusion, the prolonged static stretching did not affect active muscle stiffness with or without the stretch reflex, but tended to decrease the stretch reflex. In addition, these results imply that active muscle stiffness measured during contractions was not influenced by the stretch reflex.