Key result
Cold-water face immersion prolongs R-R intervals vs control, confirming bradycardia is driven by vagal activity.
Why the study?
Does cold-water face immersion elicit cardiac parasympathetic activity in healthy volunteers?
Does cold-water face immersion elicit cardiac parasympathetic activity in healthy volunteers?
p-value: p=<0.05
Cold-water face immersion elicits bradycardia primarily through cardiac vagal activity, independent of body position or breath holding.
Supports vagal bradycardia induction in healthy volunteers; leaves open clinical translation or therapeutic use.
BACKGROUND: Cold-water face immersion (FI) is known to produce physiological changes, including bradycardia, by stimulating the parasympathetic system. However, other factors such as sympathetic activity, intrapleural pressures, and changes in chemical mediators may also contribute to these changes. METHODS AND RESULTS: Eight healthy volunteers underwent a series of experiments designed to observe the effects of FI on heart rate and its variability, as detected using wavelet transformation. Each subject was instructed to bend over and put the entire face into an empty basin with and without breathing (protocols 1 and 2, respectively), and then perform FI in warm-water (protocols 3 and 4, respectively) and cold-water (protocols 5 and 6, respectively) while breathing and breath holding. Change in the R-R interval with FI was only significantly greater for protocol 6 than for the control procedure (protocol 1). Also, changes in the natural logarithm of high-frequency power with FI were significantly greater for protocols 5 and 6 than the protocol 1. CONCLUSIONS: Bradycardia associated with cold-water FI is mainly attributed to cardiac vagal activity, which is independent of both the change in body position caused by bending over a basin and breath holding.
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Kinoshita et al. (2006) studied Healthy volunteers (n=8). Cold-water face immersion vs. Bending over empty basin with snorkel breathing (control) was evaluated on Change in R-R interval and natural logarithm of high-frequency power (lnHF) (p=<0.05). Cold-water face immersion significantly prolonged the R-R interval and increased high-frequency power compared to control (p<0.05), demonstrating that bradycardia is mainly attributed to cardiac vagal activity.
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