Is it best to drink water or dump it on yourself to stay cool in hot weather?
As anyone nominated to do the ‘ice bucket challenge’ a while back knows well, dumping a load of chilled water on your noggin definitely feels like a pretty effective way of cooling down rapidly! And pouring water over the head is a tactic you do see being used by athletes in all sorts of sports to try to combat extreme heat. But when it comes to staying cool during a race, are you better off pouring the water you pick up at an aid station over yourself, or drinking it? And is there anything else you can do to make racing in the heat a little more tolerable?
To pour or not to pour? That is the question.
A study in 2012 set out to answer the first question by comparing the effectiveness of four approaches to cooling and hydrating during a 90 minute walk followed by a 5km time trial run in hot conditions (33 C / 92 F). The four conditions they tested were:
- Drinking nothing and not pouring water on the head.
- Drinking some chilled water but not pouring water on the head.
- Drinking nothing but pouring water on the head.
- Both drinking and pouring water on the head.
The 10 athletes who participated in the research were all runners of a good collegiate standard - so were well-conditioned to hard physical workouts - and the results showed (perhaps a tad unsurprisingly) that they all felt worst when they drank nothing and didn’t pour water on themselves during the session.
In the conditions where they did pour water on their heads, the runners reported feeling like they got the most relief from the heat and they showed a marked reduction in heart rate when they drank cold water too. However, despite these indicators, performance in the 5km time trial did not vary significantly from trial to trial. In other words, it didn’t seem to matter (in terms of out and out speed) whether the runners did nothing at all, or poured water on their heads and drank something; their running ability in a short, high intensity bout in the heat was pretty much unaffected.
In terms of actual core body temperatures, there was a marginal reduction when athletes drank and poured water on themselves. Temperature - measured with a not-too-pleasant probe up the backside I might add - was a touch lower when they drank and poured water over themselves, compared to when they did nothing! But it was a very small difference and was apparently not enough to influence running performance over 5km. (Though perhaps the prospect of a thermometer where the sun doesn’t shine to look forward to at the finish line actually slowed them down?!)
This seems to point to the fact that, for relatively short but intensive endurance events in the heat, pouring water on your head and drinking is likely to provide some psychological relief from the feelings of heat stress, but it’s unlikely to actually improve your performance by itself. There are a few caveats to this though and they’re worth considering before you decide not to bother with drinking or dousing when it gets hot…
- It’s important to note that the researchers went to lengths to ensure that the athletes started each of their test walk/runs well hydrated. This is not always the case for the rest of us in day to day training sessions so just worth bearing that in mind. If you're unsure how best to start hydrated then this might be worth a read
- In the study, athletes ‘only’ had to run a hard 5km time trial (albeit at the end of 90 min walk). Whilst this does technically fall into the category of endurance exercise, it’s not really in the same league as running a marathon, ultra, or doing an Ironman in hot weather. In the kind of events that last many more hours, it’s definitely extremely important to keep drinking to mitigate sweat losses, otherwise dehydration is highly likely to start to negatively affect performance. We've discussed how much dehydration you are able to tolerate before your performance is affected before
- As performance in longer races is extremely dependent on maintaining a positive psychological mindset, periodic cooling with a cup of cold water over the head may well provide a little mental boost that helps you stay focused and feeling better about how you’re getting on when things get tough. On a personal level, I can vividly remember running in Maui in the Xterra World Champs many years ago with my head practically boiling under the harsh Hawaiian midday sun. I ran past a chap spraying a hose pipe on his garden next to the course and begged him to turn it on me. He did and the relief I felt was fantastic and it certainly spurred me on and allowed me to keep pushing a little more than I might have done without it.
Racing in Thailand where it’s pretty damn hot, and you’ll notice I packed my white 'Brit Abroad' suntan for the occasion..
- In situations where water is a scarce resource (e.g. during a training session or event where you have to be self-sufficient), drinking should almost certainly be prioritised over dousing yourself with water, as keeping significant dehydration at bay is definitely more important than getting some transient relief from a hot head (as shown by the reduced heart rates associated with drinking in the study). However, when water is widely available, throwing some over yourself is fine if it makes you feel better too.
As an aside, one reason why athletes are sometimes told not to throw cold water on their heads in the heat is the hypothesis that this actually negatively affects thermoregulation by ‘tricking’ the brain into thinking the body is cooler than it really is, setting up a negative feedback loop that leads to an increased core temperature. Whilst this does have some theoretical basis, it seems highly unlikely that in most situations it would be possible to chill the hypothalamus (part of the brain that controls your body temperature) to such low levels that it would actually do that, so it’s probably not something to worry about in most normal circumstances.
What else can you do to remain cool in hot conditions?
Apart from drinking and throwing water on your head there are, of course, other things you can do to make exercising in the heat more bearable…
Pre-cooling (i.e. chilling yourself down before starting to exercise, to give a bigger margin for core body temperature to rise) has received a fair bit of research attention in recent years and a 2012 paper seems to indicate that it can offer some very worthwhile performance benefits, if done correctly. There are some practical challenges to overcome, as remaining cool immediately before you go out to race or train in the heat can be logistically tricky, but it’s perhaps something worth looking into if you are going to be competing in hot conditions regularly in the future. Certainly reducing warm ups to the bare minimum, staying in the shade/in air conditioning and having access to ice cold drinks in the immediate build up to the start time are ideas that you should aim to exploit where you can.
Cooling specific regions of the body is another tactic that has some merit as this article from Stanford explains in depth. Essentially, scientists now know that many mammals (including humans) have a special type of blood vessels in key areas of our bodies (notably, hands, feet and the head), as well as areas with more large blood vessels close to the surface of the skin (wrists and forearms), that make these zones the best targets for localised cooling to be applied. Research has shown that chilling these areas from the surface of the skin results in cooler blood flowing back to the centre of the body, leading to a much better central cooling effect than more generalised exposure to the cold does. Think of it as being a bit like how a car radiator works, and the reason why a long sleeved t-shirt is so much warmer than a short sleeved one on a cool day.
This knowledge can definitely be exploited by athletes in very practical ways. You might put ice or wet cold sponges under a running cap, hold them on your hands and wrists (or even stuff them up the sleeves of a tight fitting top) during a race. Alternatively, if you’re in a wilderness racing situation, stopping and submerging your hands, feet and forearms in a cold stream or similar can be very effective in getting your overall temperature down in double quick time. In a reasonably harrowing racing memory from the past, I can distinctly recall the delightful feeling of stuffing 2 or 3 ice cold sponges under my hat when the going started to get super tough on the Queen K in the Kona Ironman marathon. Whilst, sadly, it didn’t actually help me rescue what was already a disastrous performance the day (please don’t ask about my bike split, it’s not something I like to recall), it definitely felt like it helped me get through the run in better shape than I was expecting.
With all of the above said, by far and away the main thing that helps you manage your body temperature in the heat is pacing and, specifically, not going too hard, too soon in a race. Most of the thermoregulatory issues faced by the body during sport are to do with managing heat production from the working muscles and by being sensible with pacing early on in an event, you limit the chances of over cooking it from within. In other words, whilst drinking, pre-cooling, water dousing and chilling specific body parts all have a role to play in helping you keep cool, ultimately you still need to manage your output and energy expenditure carefully if you want to achieve your best performance when the temperature hots up.
Stay hydrated out there!