We examined whether the diving reflex without breath-holding (face immersion alone) increases vagal activity, as determined by heart rate variability. A group of 15 men [mean age 20 (SD 3) years, height 172 (SD 5) cm, body mass 68 (SD 9) kg] performed 12 trials at various breathing frequencies (5, 10, 15, 20, 30 breaths·min-1 and uncontrolled breath) with or without face immersion. The R-R intervals of the ECG and gas exchange variables were recorded during the 2 min of each trial. The subjects immersed their faces in 8-10°C water while breathing through a short snorkel. The subject sat in the same position either with or without face immersion. The mean R-R interval (RR(mean)), standard deviations (SD(RR)) and coefficient of variance (CV(RR)) of the R-R interval were calculated from the R-R intervals during 30-130 s. The face immersion significantly increased SD(RR) and CV(RR) (P < 0.05), and increased RR(mean) (P < 0.05) at 20 breaths·min-1. Face immersion itself had no effect on oxygen uptake, tidal volume, end-tidal O2 and CO2 partial pressures. The diving reflex without breath-holding increased the heart rate variability, indicating that face immersion alone increases vagal activity.
|ジャーナル||European Journal of Applied Physiology and Occupational Physiology|
|出版ステータス||Published - 1997 11月|
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