We have investigated the characteristics of autonomic cardiovascular regulation to bathing and post-exercise bathing (40 degrees C, 20min) in healthy middle-aged and older men (MO, 55±10 years, range: 40-71 years) compared with that in young men (Y, 22±3 years). During bathing, heart rate (HR) of MO and Y were similarly increased, and were parallel to the decreases of heart rate variability (logHF, vagal modulation) and spontaneous cardiac baroreflex sensitivity (logSBRS). The systolic blood pressure (SBP) in MO temporarily increased at the beginning of bathing, and then significantly decreased in the last phase of bathing as well as Y. The MO also showed significant decrease in SBP and diastolic blood pressure (DBP) at the beginning of the recovery phase after post-exercise bathing. In both groups, stroke volume (SV) and cardiac output (CO) significantly increased, and total peripheral resistance (TPR) significantly decreased in both bathing trials. However, TPR in MO was greater, and dilation of carotid artery diameter (systolic - diastolic) was smaller than those in Y. From these results, it was suggested that bathing attenuates spontaneous cardiac baroreflex sensitivity, and affects the regulation of fluctuations in blood pressure response in MO. Furthermore, greater attenuation of the sensitivity observed during post-exercise bathing in MO seemed to affect the blood pressure regulation in after-bath recovery phase.

DESCENTE SPORTS SCIENCE Vol.25/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE