Thirsty Work!

Thirsty Work!

How to stay hydrated for your sport.


Sport is thirsty work; your body uses water for several aspects of performance. Having a good strategy could give you the edge to perform at your best.

Whenever you exercise you lose fluid, not only through sweating, but also through water vapour in your breath. Whenever you exercise your body produces extra heat.

In fact 75% of the energy you put into exercise is converted into heat and then lost! This is why you feel hotter after exercising. Your body has to get rid of the extra heat (to keep you at 37°) so it starts to sweat. The water on your skin evaporates, taking heat energy with it. For every litre of sweat you lose (roughly 1kg of weight) your body gets rid of around 600kcals of heat energy.

Depending on the type of exercise (and you as an athlete) the body can lose fluid very quickly. The harder and longer the exercise, and the more hot & humid the environment, the more fluid you will lose. Some people sweat more than others even if in identical conditions. This can be due to fitness (the fitter and more accustomed to the environment you are the more you sweat) or size, the smaller you are, the less you will sweat.


The more you sweat, the more you should think about hydration. If you’re running a marathon you could lose up to as much as 2 litres an hour!

When you start to get dehydrated, your blood volume drops and body temperature rises. This makes it harder for the heart to pump blood around the body. The scientific consensus is that a loss of 2% of your weight through sweat will mean your maximum aerobic capacity could drop by 10% to 20%.

Weight is a great way to track hydration, and monitoring it in training is a great place to start. If you are a runner preparing for a marathon and you weigh in for a pre training run at 70kg, then after a one-hour training run, you then weigh yourself again to see how much weight you have lost. If you weighed in at 69kg you would know that you had lost roughly one litre of fluid in that hour. This gives you a guide as to how much you need to drink while you’re exercising. One kg loss in weight is roughly 1 litre of fluid loss.


Here’s our top tips for hydration around exercise:


  1. Drink before exercise – if you start off dehydrated its difficult to consume enough during exercise.
  2. Drink on thirst during exercise – It’s not very practical to weigh yourself during exercise and drinking too much can be uncomfortable, thirst is the best barometer for while you’re training. If you're thirsty, have a drink.
  3. Think about water vs sports drinks – for low intensity exercise (swimming, walking, gentle cycling) sports drinks have little benefit over water so save your money. For high intensity exercise think about having drinks that contain some carbs, not only will your body rehydrate quicker, you’ll replenish some glycogen stores as well.
  4. Drink after exercise - If you can, try to figure out how much fluid you've lost and then replenish it. Water plays a big role in recovery so if you want to stay fresh, stay hydrated.

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