Diving Response and Arterial Oxygen Saturation During Apnea and Exercise in Breath-Hold Divers
Authors: Johan P. A. Andersson, Mats H. Linér, Elisabeth Rünow, Erika K. A. Schagatay
DOI / Source: 10.1152/japplphysiol.00863.2001
Date: 01 September 2002
Reading level: Beginner
Why This Matters for Freedivers
This paper backs up a key freediving idea with real numbers: a stronger dive response (especially with cold face immersion) helps you “spend” lung oxygen more slowly during effort. If you’re doing dynamics, finning to a line, or any situation where you’re working while breath-holding, this is evidence that relaxation + face cooling can improve oxygen efficiency and delay hypoxia.
Synopsis
Freedivers often feel that cold water on the face “switches something on” — the heart rate drops, the body gets calmer, and the breath-hold feels more efficient. This study tested that effect during actual exercise, not just at rest.
Eight trained male breath-hold divers performed steady cycling at 100 W and, while exercising, did repeated 30-second apneas in two conditions: (1) apnea in air, and (2) apnea with the face immersed in cold water (10°C). The apneas were standardized: each diver started from a controlled lung volume (inhaling a set volume equal to 80% of their vital capacity) and each breath-hold lasted exactly 30 seconds. The researchers continuously measured heart rate, blood pressure, skin blood flow, and arterial oxygen saturation (SaO₂).
Both types of apnea triggered the classic dive response during exercise: heart rate dropped, blood pressure rose, and skin blood flow decreased. But when the face was in cold water, the dive response became stronger. The heart rate reduction was larger with face immersion (about a one-third drop) compared with apnea in air (about a one-fifth drop). Blood pressure also rose more with face immersion.
The key finding, though, is the oxygen story. SaO₂ fell in both conditions, but it fell less when the dive response was augmented by cold face immersion. The difference wasn’t huge, but it was consistent and meaningful: higher SaO₂ during/after the face-immersion apneas suggests the lungs were being depleted more slowly. The authors interpret this as an oxygen-conserving effect driven by reduced cardiac output and stronger peripheral vasoconstriction: less blood flow through the lungs per unit time means less oxygen pulled from the lungs, and more of the limited oxygen supply is preserved for the brain and heart.
They also discuss a trade-off that matters for freedivers: if blood flow to working muscles is restricted, the body may lean more on anaerobic metabolism (and lactate) even at workloads that normally wouldn’t create that feeling. Several divers reported “lactic acid” sensations in the legs during the apneas, which fits the idea that the dive response can protect vital organs by temporarily asking the limbs to “do more with less.”
Bottom line: during exercise, apnea alone triggers the dive response, but cold face immersion boosts it — and that boost helps maintain higher oxygen saturation, effectively stretching your usable oxygen during effort.
Abstract
This study addressed the effects of apnea in air and apnea with face immersion in cold water (10°C) on the diving response and arterial oxygen saturation during dynamic exercise. Eight trained breath-hold divers performed steady-state exercise on a cycle ergometer at 100 W. During exercise, each subject performed 30-s apneas in air and 30-s apneas with face immersion. The heart rate and arterial oxygen saturation decreased and blood pressure increased during the apneas. Compared with apneas in air, apneas with face immersion augmented the heart rate reduction from 21 to 33% and the blood pressure increase from 34 to 42%. The reduction in arterial oxygen saturation from eupneic control was 6.8% during apneas in air and 5.2% during apneas with face immersion. The results indicate that augmentation of the diving response slows down the depletion of the lung oxygen store, possibly associated with a larger reduction in peripheral venous oxygen stores and increased anaerobiosis. This mechanism delays the fall in alveolar and arterial PO₂ and, thereby, the development of hypoxia in vital organs. Accordingly, we conclude that the human diving response has an oxygen-conserving effect during exercise.