Have you ever finished a race in a sweaty, sopping mess, your kit wallpapered to your body and your hair looking like you've just been for a fast spin in a washing machine?
Sweating is an inevitable - and essential - by-product of exercise but that doesn't mean you have to like it. Thankfully, there are steps you can take to compete in greater comfort.
Why we sweat
The body's normal temperature is around 37°C, but it can rise in summer, during exercise or when we are ill. Our body regulates this via evaporation, in the form of sweat, to cool us down. "Our circulatory system is like a radiator to dissipate heat," says Dr Dominic Micklewright, a sport and performance expert at the British Association of Sports and Exercise Sciences. Sweat is mostly water, but also contains sodium, chloride, potassium, calcium and other minerals.
Battle of the sexes
Men's sweat glands are more active than women's and men generally sweat sooner. "Also, men have a larger surface area," says Micklewright. "The larger the surface area, the easier it is to dissipate heat."
Women take note, however: body temperature rises half a degree when you are ovulating or menstruating. This is not a reason not to compete or train, but be aware that you may sweat more, even at rest, than at other times in your cycle.
You may well ask this if you sweat a lot, but the biggest factor, aside from gender, is out of your control: your genes. "There is no formula," says Micklewright. "Drink to your thirst response, and don't drink too much. If you over-hydrate, you dilute the sodium in your body, which can lead to hyponatraemia and, in extreme cases, death."
It's important to become used to racing conditions, even if it's a sprint race in a UK heat wave rather than an Ironman in Hawaii. "It's better to get out there than to hide away," says Simon Ward of www.thetriathloncoach.com. "Be sensible. You should be tapering your training before a race, so walking around in the heat is often enough, combined with light training."
Off-road races may offer more shade and less congestion than city races and coastal races can be breezier, which won't stop you sweating but will make you feel more comfortable. "Whatever the race, it's important to be as lean as possible; the more fat you store the less responsive your body is to high temperatures," says Ward. "Avoid dark colours and wear a white cap to shade your face. There's no evidence that pouring water over your head cools you down, but putting your hands and feet in water can cool the blood being pumped back to your heart." Some triathletes wear an ice vest before a race on a hot day.
"Many people finish a race and say the heat defeated them, but usually they've gone too fast, not hydrated enough or not paid enough attention to replacing electrolytes," says Ward. "Many triathletes I've coached take the sensible approach and perform better as a result."
The day the heat was on
How the professionals learned important - and hard - lessons about racing in high temperatures
Simon Ward, triathlete and coach
"I did the Marathon des Sables and everyone was scared of the heat - the hottest day was over 60°C. But it was dry heat, so the sweat dried on the skin and cooled us down. It was probably better than running in 30°C heat with the humidity in the UK."
Tim Don, 2006 ITU World Champion
"At the 2005 World Championships in Japan I collapsed on the run through heat exhaustion. The lake was about 30°C, which I didn't take into consideration. Also, the bike was harder than I'd expected and I did not have time for all my energy drink. Lessons learned."
Helen Jenkins, 2008 ITU World Champion
"I once had a problem at the Windsor Triathlon with heat exhaustion - I hadn't drunk enough the day before the race, which was freakishly hot. I felt incredibly thirsty for the whole bike ride and the last lap of the run was a blur. Now I start hydrating three days before a race."