Drinking while running definitely is not easy. Unless you grasp the cup carefully, you can spill half the contents on the ground. If you gulp too quickly, you can spend the next mile coughing and gasping. If you dawdle at aid stations, you can waste precious seconds. And if you gulp down a replacement drink you aren't used to, it might make you nauseous.

Drinking on the run is a science — and so you need to practice. Do this during your training runs, particularly your long training runs. Drinking on the run is necessary for survival. Here's why:

During exercise, the body usually produces more heat than you can get rid of by sweating.

A marathoner's body temperature gradually rises three to four degrees to 102 degrees Fahrenheit, an efficient level for energy utilisation.

At this point, your air-conditioning system is in synch with the environment and you perform well. If the weather is too hot or too humid, or you become dehydrated — resulting in a drop in sweat production — the body's temperature can soar to dangerous levels. Your muscles will not perform efficiently at temperatures that are too high (over 104F), so that will slow you down.

This is an important defence mechanism, because if you fail to sweat and your core temperature rises past 108F, you may suffer heat-stroke, a potentially serious problem that can cause headaches and dizziness, and in extreme cases convulsions, unconsciousness, and death. What strategies can runners use to avoid problems on hot days?

1. Drink before running.

Drink adequately and drink often up until two hours before the start. Excess body water will be passed as urine before you start to run. Two hours before, however, stop drinking otherwise you'll be ducking into the bushes.

2. Drink while you run.

Just before the gun sounds, you can start drinking again. Once you're moving, you'll sweat off any excess liquid before it reaches your kidneys. You also need to drink frequently while training, especially during warm weather. You'll run faster and recover sooner. Carry a water bottle if necessary.

3. Walk to drink.

Don't try to gulp it down while running through the aid stations. You'll be able to drink more if you stop or at least walk. You'll lose less time than you think.>

4. Drink after running.

Drink as soon as you stop, but even after your initial thirst is quenched, you still need to keep drinking. One sign of your hydration level is to check your urine. Clear urine is a sign of good hydration.

5. Don't overestimate your ability.

Realise that you can't run as fast when it's warm. Don't expect to set a personal record, and don't be afraid to bail out early (at least start slowing down) when you're starting to overheat.