Dr Heather Massey is a researcher at the University of Portsmouth’s Extreme Environments research group and a seasoned open water swimmer. Having swum the Channel and competed in the world ice swimming championships, her research into the effects of extreme temperatures on the body is personal.
During lockdown the number of people enjoying wild swimming soared, but so did the number of deaths. Massey’s research examines whether cold water swimming is more likely to kill or cure.
Now that temperatures are rising, those rivers and lakes are looking extremely tempting. Why do we find open water so appealing?
There is a huge amount of experiential anecdotal evidence that shows people find outdoor swimming transformative. It changes their outlook. They feel more connected to nature. It’s their reset button.
Yet even on a warm day the water can still be cold enough to take your breath away. What happens to our bodies when we get into cold water?
The skin cools down very rapidly and we experience the cold shock response, that gasp followed by uncontrolled breathing. If your airway is under the water – say you’ve jumped or fallen in – you risk drowning. That initial gasp can be a couple of litres of air – more than enough for a lethal dose of water.
The cold shock makes our hearts work a lot harder too, which can cause heart problems. And when the blood pressure goes up suddenly, the cold shock response can cause issues such as a bleed on the brain.
Sudden death on entry to the water doesn’t sound all that appealing. How do you avoid it?
Initial immersion in cold water should be done in a gradual way so the airway is kept above the water. You do see lots of open water swimmers diving in, but they’ve probably spent many years getting used to the cold, so their cold shock response is much less severe than someone who has never done it before.
The cold shock response does pass. After one to three minutes you should be able to talk in normal sentences. Now you’ve got control of your breathing you can start swimming or, if you’ve fallen in by accident, thinking about how to get out.
Once you’ve recovered from the initial shock, what’s next?
After you’ve cooled the skin, you start to cool the superficial nerves and muscles. There’s about 3% reduction in muscle strength for every degree that the muscle cools. When the muscles cool to about 27C, they start to fatigue. This means you’ll tire much more easily than you would in a pool.
You’ll become uncoordinated, your stroke length will shorten, you’ll become less efficient in the water, your sinking forces will increase. Then comes swim failure and drowning.
I’ve experienced claw hand – a lack of coordination in the hands. My hands became very stiff and I couldn’t form a paddle to swim with. The muscles in my arms and forearms were so cold they were no longer contracting as I wanted them to. That’s when I knew it was time to get out.
Hypothermia happens when the body temperature drops to below 35C. How do you spot someone who’s in trouble?
It takes 20 to 30 minutes to cool the deep body to an extent that you reach clinical hypothermia. Loss of awareness and changes in vision are signs that someone is becoming hypothermic. Look for the “umbles” – fumbling, grumbling, stumbling and mumbling.
I’ve supported a number of people in the lab and after ice swims. It’s not a pretty sight, seeing someone who is hypothermic. It’s debilitating and dangerous. It’s important that you get them out of wet clothes and into a warm, dry environment as quickly as possible.
So, you’ve got through the cold shock, enjoyed your swim and exited the water before your muscles stop doing as they’re told. You’re safe now, right?
Actually, when you get out of the water your body continues to cool. A feeling of euphoria is common among open water swimmers when they get out. They want to take it all in, to stand and stare at what they’ve just swum in. It’s completely natural, that post-swim high. However, it’s really important that you dry and dress quickly. Delaying will only exacerbate any continued cooling as the water starts to evaporate from your skin – a very effective way of losing heat. We have to rewarm from the outside in. The cooling will continue until the warmth finally reaches the deep body. Only then will the body temperature start to rise.
Wild swimmers don’t get colds or suffer pain, they live long, happy and healthy lives… these are just some of the stories you might hear. But what do we really know about the positive effects of swimming in cold water?
We’re seeing anecdotal evidence of people experiencing changes to their mental and physical health, with improvements in conditions like migraines and a reduction in menopausal symptoms. Cold water immersion can, in some instances, reduce inflammatory responses, and we’ve seen evidence that people take fewer days off work when they shower in cold water.
A recent study by Cambridge University found that people who swim in cold water have higher levels of a protein linked to the formation of synapses, the links between nerves. The theory is, if you have a higher level of this protein, it will reduce neural degeneration and so stave off dementia.
We also think people can reduce some symptoms of depression if they go outdoor swimming. We’ve just completed a study with people who have been living with depression and the information is looking quite positive, but we don’t have all the answers just yet.
So, we’re starting to get a breadth of information – quantifiable evidence – of the effect cold water immersion has on mental and physical health conditions. The next step is to look at causal effects rather than just relationships. We need to investigate: what is the cause? Is it due to the physiological responses to that cold water?
Cold water swimming is not accessible to everyone. We need to find out if there are other ways that people could benefit. Can we dip a forearm in cold water and have the same experience? What if you splash cold water on your face? Does that give you the same level of effect? Or is it about being in a social group? Is it the exercise that is key? This is what we as scientists need to unravel.
So, given all the dangers and lack of concrete evidence of the positive effects, what draws you to open water swimming?
The level of evidence is still skewed towards effects being harmful, but that’s because the research into the benefits hasn’t caught up. I think we need to challenge our bodies. We do a lot of sitting, a lot of staring at Zoom. I think we need to push ourselves both physically and mentally.
I’ve always swum. I spent my childhood down at the beach, always in and out of the water. Now I live about 300 metres from the sea so I’m very lucky, I can just go down any time of year and dip my toe. I went swimming last night and I’ll go this evening, when it’s calm and quiet.