Is it too hot to run ?

June 2017

You have been waiting for months and finally here it is: Summer. Rain showers are just a bad memory and cold winds have become part of History. It’s nice and warm outside. But could it be too warm to exercise? It is difficult to provide a single answer which could apply to all situations, and for all sportsmen/women. But at least we can relate key facts that should prove valuable when you decide to go for a run, complete your crossfit routine or even play basketball outside this summer.

In a previous post we mentioned the vital need to maintain your body at around 98 °F (37°C). A few degrees warmer may be beneficial for performance: it helps your muscles optimize their contraction. However, you really do not want to get too hot. Not only does it reduce your performance and ability to exercise, but it can also be dangerous. As you exercise your body produces heat, which is fine so long as you can get rid of this extra heat by sweating, for example. However, if you exercise too hard, too long, and if it is too hot outside, then you cannot evacuate this heat. It is stored and your body temperature rises to stressful levels.

Heat-related injuries may occur if your body temperature rises above 104°F (40°C). They range from heat exhaustion, illustrated by the inability to continue exercising, to heat stroke, a real cause of emergency. Although these conditions are fairly rare, they deserve full attention and medical care. But before these serious signs can be observed, one phenomenon insidiously sets in: dehydration. For the average man, dehydration starts when 25 fl.oz. (0.75L) are missing from the body. When exercising hard in the heat, this amount can be lost through sweating in 25 minutes! It can cause some rather annoying reactions like heat cramps and heat syncope. If the former is just painful, the latter is more serious. This fainting is due to a lack of body fluid as you exercise in the heat. The brain does not receive enough blood. If this happens to someone place them in a cooler place, horizontally, and try to re-hydrate while waiting for medical assistance.

So, to err on the side of caution, I would not recommend exercising in the heat. But if you keep in mind the following advice, and make sure you are fit and healthy, then you may be able to enjoy short exercise sessions at moderate intensity this summer.

Trained athletes are more capable of dealing with exercise in the heat, especially when they have conducted some of their sessions in warm environments. They sweat (and thus cool) earlier, their heart functions better and overall, they outperform those who have not trained in the heat. So, before you go for 20 miles for your first run of the year this weekend, train in moderate heat over the course of 2 weeks. 10 sessions of 90 minutes each, at a pace where you can still speak with your running mate(s). The most important is to make sure you are fully hydrated before you start. How do you know? Drink as soon as you feel thirsty at least 12 hours before and keep an eye on the color of your urine: the clearer the better.

Pre-cooling strategies are also quite efficient. You can try to cool before you go by having a cool shower or bath, or by immersing your hands & forearms in cold water from the tap for 10 or 15 minutes. In addition, you could start your session with a wet t-shirt to provide a long-lasting cooling effect.

Stay at rest during the hottest part of the day, and for the sweat to be efficient at cooling you when you exercise, avoid hot and humid conditions. During the session, dress light, and stay away from waterproof gear at all costs, even if you think it will make you lose weight (more on this myth in a future post). Drink a glass of cold water with some salt and sugar every 15 minutes. Wet your head, torso and hands/forearms as often as you can. Protect your head from the sun, and listen to your body; if you feel dizzy, sick, have goose bumps, short shivers, or simply cannot continue, then stop. Seek shade or a colder place, drink water and spray it on your body while waiting for medical assistance.

After the session, you need to replace the fluids you have lost, especially if you intend to go for another session the next day. Sweat is basically salty water. It needs to be replaced by drinking… salty water. A good pinch of salt for every quarter of a gallon (1g per litre) will ensure an optimum replenishment of your body fluids. By the way, this is just enough to make it taste rather unpleasant. Sorry! Make sure it is cold to help you cool quicker. Drink at least the amount you have lost (body mass pre- and post-exercise is a good indicator). Finally, before, during, or after the session, avoid energy drinks which are much too sugary, do not contain enough salt, and have yet to prove their efficiency regarding performance enhancement. Have a good night of sleep in a cool environment, especially if you intend to train again the next day.

So, to continue your workout routine this summer, don’t push too hard or too long, and drink!