Myth busting: is cold water immersion bad for women?

Recently there have been suggestions across social media about how cold water immersion is “bad for women”. It sounds authoritative, but it’s not supported by evidence, says Dr Heather Massey

Research from the Extreme Environments Laboratory at the University of Portsmouth has repeatedly examined whether women respond differently to cold water. The consistent finding is simple: when men and women are matched for body size and composition, their responses are remarkably similar.

Take the cold shock response, that involuntary gasp, rapid breathing and racing heart that hits in the first seconds of immersion. In a large dataset analysed by Clare Eglin, Heather Massey and Mike Tipton, both men and women showed substantial increases in breathing rate and heart rate on immersion in 15.6°C water. Men displayed larger absolute tidal volumes and gasps, but this reflected larger lung volumes. The relative increase from rest was similar. Breathing frequency, a key indicator of ventilatory drive, rose to a comparable extent in both sexes. The reflex is human.

Cooling of the extremities tells the same story. Earlier work suggested women’s fingers cooled faster than men’s. However, studies led by Ollie Jay and George Havenith demonstrated that once hand size was accounted for, the apparent sex difference largely disappeared. Smaller hands cool more quickly because they contain less heat and have a higher surface area relative to volume. This is physics, not physiology.

The feet follow suit. In a similar study at Portsmouth matching male and female participants for foot volume, toe skin cooling rates were the same. Thermal comfort and sensation were also similar. Again, morphology, not sex, predicted cooling behaviour.

Even during prolonged immersion, the pattern holds. Research led by Peter Tikuisis found that when body mass, surface area to volume ratio and body composition were considered, men and women exhibited comparable metabolic heat production and core cooling rates in cool water. Differences that do emerge in mixed groups typically reflect the fact that men are, on average, taller and more muscular, while women often carry a higher proportion of body fat. These characteristics influence heat storage, insulation and heat production.

As Dr Massey summarises, there are no inherent differences in cooling responses between men and women when they are matched for body mass and composition. If a man and a woman are the same size and have similar fat and muscle mass, their cooling responses would be expected to be similar.

Cold water does not discriminate. It responds to surface area, insulation and metabolic heat. The message is reassuringly straightforward: prepare well, acclimatise progressively, respect the conditions and judge risk by individual build and health.

Full scientific articles references in the order they appear in the text

1. Eglin C et al. (2019) Initial responses to cold water immersion in men and women; Proceedings of the International Congress on Environmental Ergonomics 2019 The Netherlands. https://easychair.org/ smart-program/ICEE2019/2019-07-12. html#talk:106622

2. Jay O et al., (2004) Jay, O., Havenith, G. Finger skin cooling on contact with cold materials: an investigation of male and female responses during short-term exposures with a view on hand and finger size. Eur J Appl Physiol 93, 1–8 (2004). https://doi.org/10.1007/s00421-004- 1146-x

3. Massey H et al., (2017) Size does matter! Conductive toe skin cooling in matched male and female volunteers: Proceedings of the International Congress on Environmental Ergonomics 2017 Japan. https://icee2017.h.kobe-u.ac.jp/ ICEE2017_c/Scientific_Program_files/ Programme%20Schedule_ICEE2017.pdf

4. Tikuisis P et al. (2000) Comparison of thermoregulatory responses between men and women immersed in cold water. J Appl Physiol 2000 89:4, 1403-1411 https://doi. org/10.1152/jappl.2000.89.4.1403