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Brain blood flow and hyperventilation on cold water immersion: can treading water help control these symptoms of cold shock?


Cold-water immersion (CWI) elicits the cold shock response (CSR). The hyperventilatory component of the CSR causes a decrease in cerebral blood flow velocity (CBFv) potentially causing sensations of dizziness and increasing the risk of becoming unconscious and consequently drowning [1]. In these early minutes of CWI the current advice is to 'float first' and remain stationary [2] yet this strategy may not have any effect on ventilation and therefore brain CBFv. We tested the hypothesis that leg only exercise could offset the reduction in CBFv in a resting CWI (H1) and be absent in warm water immersion.


Seventeen participants consented and visited the laboratory 3 times; mean [SD]: age 21 [3]yrs; height 1.71 [.01]m; mass 70.9 [10.1]kg. All immersions were standardised by depth, duration, clothing (bathing suit) and time of day. Test conditions were a) a resting warm water immersion (WWI; 34.7 [2.6] °C), b) a resting CWI (CWI-R: 12.2 [0.5] °C), c) a CWI (12.1 [0.5] °C) where light exercise (leg kicking/treading water; 80 bpm-1) commenced 30-seconds after water entry (CWI-K). CBFv was measured using a transcranial Doppler at a fixed depth (61 [1] mm) over the middle cerebral artery. Oxygen uptake and ventilation were measured using an online gas analysis system. Perceptions of breathlessness were measured after 1, 3 and 5 minutes using an 11-point categorical scale (0-not at all breathless, 10-extremely breathless). ANOVA was used to analyse the data to an alpha level of 0.05.


CWI induced significant changes in contrast to WWI (see Table 1).

Table 1 Mean [SD] perceived breathlessness, CBFv, oxygen uptake, and carbon dioxide production in WWI (condition a), CWI-R (b) and CWI-K (c); letters denote differences between the corresponding condition.


Leg kicking on CWI partially offset the reduction in CBFv that normally occurs on CWI; in contrast to a warm water control. WWI CBFv was only different to the CWI-R condition. This did not alleviate symptoms of breathlessness despite increased oxygen uptake and carbon dioxide production in the CWI-K condition; the hypothesis is only partially supported.


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Correspondence to Martin Barwood.

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This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated.

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Barwood, M., Burrows, H., Cessford, J. et al. Brain blood flow and hyperventilation on cold water immersion: can treading water help control these symptoms of cold shock?. Extrem Physiol Med 4 (Suppl 1), A40 (2015).

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