Characteristics of heart rate response to activation of muscle metaboreflex in humans

 

Kazuhito Watanabe¹, Masashi Ichinose², Naoto Fujii¹, Mayumi Matsumoto¹, and Takeshi Nishiyasu¹

¹Institute of Health and Sports Science, University of Tsukuba, Tsukuba City, Ibaraki, Japan; ²School of Business Administration, Meiji University, Tokyo, Japan

 

We tested the hypothesis that there is a large individual difference in heart rate (HR) response to activation of the muscle metaboreflex by postexercise muscle ischemia (PEMI), and the individual difference is influenced by cardiac autonomic tones and/or the arterial baroreflex function in humans. Forty healthy subjects performed a 1-min isometric handgrip exercise at 50% maximal voluntary contraction followed by a period of imposed PEMI. To obtain cardiac autonomic tones and the sensitivity of arterial baroreflex (BRS), autospectral power for the R-R interval (RRI) and the transfer function gain for the relationship between arterial pressure and RRI, respectively were analyzed. Although mean HR was not changed from rest to PEMI, the variance of individual changes in HR from rest to PEMI was larger than that from rest to the recovery period subsequent to PEMI (P < 0.05). The change in RRI by PEMI was correlated with changes in the RRI power in high-frequency range (r = 0.589, P < 0.01) and the transfer function gain in low-frequency range (r = 0.495, P < 0.01). We suggest that, in humans, there is a large individual difference in HR response to activation of the muscle metaboreflex, and the individual difference is influenced by changes in cardiac parasympathetic tone and BRS.

 

Key words: individual difference in heart rate response, cardiac autonomic tone, baroreflex sensitivity