Cardiovascular Responses to Cold-Water Immersions of the Forearm and Face, and Their Relationship to Apnoea
Authors: Johan Andersson, Erika Schagatay, Anna Gislén, Boris Holm
DOI / Source: https://doi.org/10.1007/s004210000317
Date: 18 July 2000
Reading level: Beginner
Why This Matters for Freedivers
This helps explain a classic freediving experience: why your heart rate can drop fast with cold water on the face, and why “getting cold” elsewhere doesn’t necessarily boost the dive reflex the same way—especially once you’re already holding your breath. It’s also a reminder that face/forehead cold is a powerful switch for the diving response, which matters for both performance and safety (bradycardia + blood pressure changes).
Synopsis
Freedivers often talk about the “dive reflex” like it’s one single thing, but your body is actually juggling different reflexes at the same time. Cold water on the skin can trigger a thermoregulation response (basically: “save heat”), while breath-holding and cold water on the face trigger the oxygen-saving diving response (“save oxygen for the brain and heart”). This paper asks a simple, practical question: if cold water on the face slows the heart (bradycardia), and cold water on an arm can push the heart rate the other way, what happens when you combine them—especially during apnea?
The researchers tested healthy volunteers with cold water at about 9–11°C and compared different conditions: forearm in cold water while breathing normally, face in cold water while breathing normally, both together, and then similar combinations during breath-holding. They tracked cardiovascular changes, focusing mainly on heart rate and the typical “diving response” pattern.
When people were breathing normally, the forearm cold exposure tended to cause a small increase in heart rate (a mild “cold stress” response), while face immersion tended to cause a clear decrease in heart rate (the classic diving bradycardia). When both were applied together while breathing, the effects combined: the face still pulled the heart rate down overall, but the forearm cold nudged it upward a bit—like two hands on the same dial, turning in opposite directions.
But the most interesting part is what happened during apnea. Once breath-holding entered the picture, the face-driven diving response basically took priority. The added forearm cold didn’t meaningfully change the heart-rate response during apnea. In other words: when there’s a “threat of asphyxia,” the body seems to choose oxygen-saving rules over temperature-saving rules.
A useful takeaway for freedivers is that not all “cold” is equal. Cold water on the face is a strong trigger for the diving response and bradycardia, while cold on an extremity may influence circulation and heart rate during normal breathing—but it doesn’t necessarily “supercharge” the diving response once you’re already in apnea mode.
Abstract
Apnoea as well as cold stimulation of the face or the extremities elicits marked cardiovascular reflexes in humans. The purpose of this study was to investigate whether forearm immersion in cold water has any effect on the cardiovascular responses to face immersion and apnoea. We recorded cardiovascular responses to cold-water immersions of the forearm and face in 19 (part I) and 23 subjects (part II). The experimental protocol was divided in two parts, each part containing four tests: I1, forearm immersion during eupnoea; I2, face immersion during eupnoea; I3, forearm and face immersion during eupnoea; I4, face immersion during apnoea; II1, apnoea without immersion; II2, forearm immersion during apnoea; II3, face immersion during apnoea; and II4, forearm and face immersion during apnoea. The water temperature was 9–11 °C. Cold-water immersion of either the forearm or face was enough to elicit the most pronounced thermoregulatory vasoconstriction during both eupnoea and apnoea. During eupnoea, heart rate responses to forearm immersion (3% increase) and face immersion (9% decrease) were additive during concurrent stimulation (3% decrease). During apnoea, the heart rate responses were not affected by the forearm immersion. The oxygen-conserving diving response seems to dominate over thermoregulatory responses in the threat of asphyxia. During breathing, however, the diving response serves no purpose and does not set thermoregulatory adjustments aside.