The 1 minute per degree myth

Heard the one about 'you can stay in 1 minute per every 1 degree?' It's not true

Kate in Alpkit Dulsie

At some point, someone, somewhere, tried to simplify winter swimming and came up with the rule of thumb that you can stay in ‘one minute per degree’. The rest is history: now it’s treated as an actual fact, something to aspire to, and (worse) something to outdo.

So if we can all stay in a minute for every degree, how come some of us, doing that, get out feeling completely lousy if not hypothermic? How come some people really suffer and don’t feel right for the rest of the day – and others get out mad for repeating it all again tomorrow? Because every body is different, and the rule of thumb is not actually true.

People rarely get competitive about being able to endure heat in a sauna, I’ve never heard anyone expect us all to run at the same speed and yet when it comes to cold there’s a remarkably pervasive belief that we’re all the same. We are not, and here are six solid physiological reasons why the one minute rule does not work:

  1. In terms of cold sensitivity, overall mass matters: large objects take longer to cool than small ones, and similarly a big person will take longer to cool than a small one.
  2. Surface area to volume is also important when it comes to cooling: a tall slender person will cool down faster than a shorter stockier one.
  3. Body fat (measured by ‘skin fold thickness’) also assists the retention of warmth. When you get in cold water, blood withdraws from the surface of skin, turning this fat into ‘bioprene’. It’s like having an internal wetsuit that helps insulate your core. Women naturally hold more body fat than men, and a more even distribution of subcutaneous fat, which provides some insulation, but swimming perfuses muscles with blood close to the skin surface, so if you are exercising in water body fat is not as advantageous as it would be if you were stationary.
  4. There are ‘fast coolers’ and ‘slow coolers’. When there are disasters at sea with people thrown overboard they perish at different rates, as baseline cold sensitivity is as widely distributed as any other physical trait (survival of marine disasters is where a lot of this science comes from). Just as there are people who can run marathons in the desert, and others who feel poorly on a hot summers day, people arrive at cold swimming with different baselines. Put a group of similar size, similar weight people into a cold situation – whether that is a drafty kitchen or a river in winter – and some will be comfortable, and others not.
  5. Lifestyle matters: for some, cold is a way of life. Those who work outdoors, live in cold houses, or expose themselves to cold regularly (through swimming or any other outdoor activity) will be better adapted to cold than those with warm lives.
  6. Day to day, cold tolerance is likely to fluctuate with overall health – stress, lack of sleep, hangovers and being under the weather are all likely to weaken your resilience.

So, how long might a swim last when winter comes? Before the Hoff most winter swimmers were talking about very short immersions – counting strokes, not minutes. The OSS are firm believers in doing what you like, what brings you joy and what feels right for you. We hear many (many!!) accounts of people who don’t like winter swimming at all – it feels brutal, it makes people sleepy and inefficient at work, it involves so little actual exercise it doesn’t make the best use of exercise/me time. There are those who find some days a winter swim takes all their worries and washes them over the weir, and other days it ‘just doesn’t feel kind’.

Whatever you do, go gently, have fun, drop the macho-minute-per-degree nonsense, and do it for you.

  • This feature is an edited version of material in The Outdoor Swimmers’ Handbook by Kate Rew, which has chapters on Understanding Cold, and Winter & Ice Swimming. Also available signed in the OSS shop.
  • The information in this feature is drawn from the academic research work of Mike Tipton from the Extreme Environments Laboratory at the University of Portsmouth, and Heather Massey, also at the University of Portsmouth.
  • For more features on Cold, see the Understanding Cold section of Survive.



Kate Rew
Tim Bridges