I’m training for a long-distance race this summer. After watching London marathon runners suffering from dehydration on television, I’m concerned that I’ll put my health at risk while exercising when it’s hot. What can I do to make sure this doesn’t happen?
Don’t be alarmed. More than 35,500 runners successfully complete the London marathon with no abnormal after-effects. As well as being pretty resilient, our bodies are remarkably adaptable, providing we encourage them in the right kind of way.
Above all, this means sound preparation. Hopefully you are following a training schedule that gradually increases your running distances. But it is a good idea, also, to do some strength and speed training so that your cardiovascular system and muscles are working at top efficiency. The more well-tuned your body, the less likely you are to overheat during the race. Sound preparation also means good nutrition, good sleep and rest days built in to your schedule.
Many long-distance races are run at cooler times of the day. But if you know you are going to be running in high heat or – equally important – high humidity, you should try to do some training in similar conditions. Sitting in very hot baths or jogging in a wet suit are poor substitutes!
Perhaps the most confusing issue is how to stay properly hydrated during your race. The “right amount” of fluid depends on many variables, including your weight, running speed, sweat rate, fitness level, heat and humidity on the day, how much breeze there is and so on. Official advice says you should drink as much as you can comfortably tolerate. That means don’t upset your stomach: if you develop symptoms such as nausea, stomach cramps or diarrhea during the race, do not ignore them.
If your race lasts one hour or less and you are not running at élite pace, the chances of getting seriously dehydrated are minimal. Just ensure you are fully hydrated beforehand, and take regular sips of water at the drinks stations. For longer races, the guidelines suggest you drink just over half– to just over one litre (600 to 1,200ml) per hour. And you should definitely include some carbohydrate and nutrient replacements in your drink. An “isotonic” sports drink is very useful for this.
If you want to be a bit more scientific in your approach, weigh yourself immediately before and after a long run. The difference in your body weight will be fluid lost through sweat: if you lose 0.5kg during a one-hour run, this equates to half a litre. So that’s how much you’ll need to drink per hour.
With good preparation, you have nothing to fear. Remember people run ultra-marathons in the Sahara and survive just fine! The bottom line is, listen to your body on the day, and don’t be too proud to slow down or quit if something feels wrong. There’s always another race to enter on another day…