Changes in Blood Circulation of the Tendons and Heart Rate Variability During and After Acupuncture

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 acupuncture-induced 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 (StO₂) of treated and nontreated tendons were measured using red laser lights. In addition, HRV was also measured during the experimental period. Results: THb and StO₂ of the treated tendons significantly increased during acupuncture, and then remained high during the recovery period. THb and StO₂ 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.