It is, in case you hadn’t noticed, cold outside. At the same time, a sizeable chunk of the population is planning to get fitter this year. With millions hitting the roads, fields and possibly even lakes over the coming weeks, the obvious question is: how cold is too cold? There’s nothing wrong with channelling your inner Rocky Balboa, but might you be risking your health – or even your life – by braving the frost? And what can you do about it?
Firstly, it’s important to understand that exercising can make it tougher to perceive a shift in body temperature. In one recent study, researchers partially submerged 11 healthy young men in a tank of cold water and had them either rest or do low-intensity cycling, monitoring their oxygen uptake, body temperature and perception of cold. The results were slightly surprising: even though the subjects’ core temperature was roughly the same in both tests, exercise slightly blunted their shivering response and ability to feel the cold. It’s not clear from the study whether exactly the same thing could happen in cold air, but it’s a cause for concern.
Hypothermia, in case your mountain survival skills are rusty, is what happens when your body loses heat faster than it can generate it, leading to a drop in body temperature to below 35C (about 37C is considered normal). This is a medical emergency that demands attention, and though it’s not common among exercisers, it can occur even among veteran runners – in the 2018 Boston marathon, unusually cold temperatures meant that several elite contestants were affected.
“I’d say the most important concern is people going out unprepared for what could happen,” says Dr Clayton Cowl, a pulmonologist at Mayo Clinic in Minnesota. “People are unlikely to get too cold while they’re in the middle of a planned run, but for people not used to being out in cold weather, there can be a tendency to not be prepared in terms of appropriate apparel or preparation. Something we regularly see with drivers is people going out in normal clothes and relying on the heater in their vehicle – but then if they break down in a rural area, there might not be help for them for quite a time frame.”
Something similar can happen with runners: if your run comes to an unplanned stop due to injury or exhaustion, for example, you’re unlikely to be dressed for the cold, and being low on blood sugar or dehydrated can make matters worse. To be prepared, then, go out wearing layers, and make sure your hands and head are covered. “You lose heat quickly through your head,” says Cowl. “And if your temperature drops, your extremities can get cold very quickly, leading to the additional risk of frostbite if it’s cold enough.”
If things go wrong, it’s important to recognise the warning signs of hypothermia: if you or a friend is shivering uncontrollably, losing coordination, or starting to slur speech or feel confused, it’s time to take action. “Obviously, the key thing is to get out of the cold as quickly as possible,” says Cowl. “And once you’re somewhere warm, also try to get rid of any wet clothing that might be contributing to the effect. But something people often get wrong is trying to warm themselves too quickly – excessively hot water or heating pads can damage the skin, or even cause heart irregularities.” Warm drinks are a better option – sip them slowly – as is layering blankets on top of someone who’s shivering. In moderate cases, this might be enough, but in more extreme circumstances – including if someone passes out – you should get them off the cold ground, monitor their breathing, and get medical attention as quickly as possible.
As always, though, prevention is better than cure, so if you’re up for some winter fun, take plenty of layers (and maybe a flask of tea), and let a friend know where you’re going. If you’re swimming, make sure you get a proper cold-water induction, with an expert talking you through the dos and don’ts. There are plenty of benefits to getting out in the open air – as long as you’re planning it properly.
