Hydration & exercise tips

Strathmore Water is delighted to supply bottled water for the Edinburgh Marathon Festival. Strathmore’s partnership with EMF ensures that all participants have easy access to bottled water throughout the event so that they are able to keep themselves properly hydrated.

Exercise is thirsty work. Whenever you exercise you lose fluid, not only through sweating but also as water vapour in the air that you breathe out. Your body’s fluid losses can be very high and, if the fluid is not replaced quickly, dehydration will follow. This will have an adverse effect on your physical performance and health. Exercise will be much harder and you will suffer fatigue sooner.

WHEN, WHAT AND HOW MUCH FLUID SHOULD YOU DRINK?

You can estimate your sweat loss and, therefore, how much fluid you should drink by weighing yourself before and after exercise. Every 1kg decrease in weight represents a loss of approximately 1 litre of fluid.

HOW MUCH FLUID DO I LOSE?

The amount of sweat that you produce and therefore, the amount of fluid that you lose, depends on – how hard you are exercisin, how long you are exercising for, the temperature and humidity of your surroundings & individual body chemistry.

During 1 hour’s exercise an average person could expect to lose around 1 litre of fluid.

WHY DO I SWEAT?

When your muscles start exercising, they produce extra heat. In fact about 75% of the energy you put into exercise is converted into heat, and is then lost. This is why exercise makes you feel warmer. Extra heat has to be dissipated to keep your inner body temperature within safe limits – around 37 – 38 degrees C.  The main method of heat dispersal during exercise is sweating. Water from your body is carried to your skin via your blood capillaries and as it evaporates you lose heat. For every litre of sweat that evaporates you will lose around 600kcal of heat energy from your body.

Before Exercise

Your main priority is to ensure you are well-hydrated before exercise. It is clear that if you begin a training session or competition in a dehydrated state your performance will suffer and you will be at a competitive disadvantage. Prevention is better than cure. Make sure you are well hydrated before you begin exercising. The American College of Sports Medicine and the American Dietetic Association and Dieticians of Canada recommend drinking 400 – 600 ml of fluid during the two hours before exercise to promote hydration and allow enough time for excretion of excess water.

During Exercise

As soon as you start exercising you will start to lose fluid, so your aim is to offset fluid losses by drinking early and at regular intervals. A small net fluid loss, equivalent to less than 2% of your body weight, is unlikely to affect your performance. However, greater losses will result in a drop in performance so you should limit dehydration to less than 2% of your body weight (IOC, 2004, Coyle, 2007). For example this would mean 1kg for a 50kg person, 1.5kg for a 75kg person and 2kg for a 100kg person.

MARATHON – If you are planning on running the marathon drink no more than 800ml per hour.

After Exercise

In order to restore normal fluid balance after exercise, researchers recommend you should consume approximately 1.2 – 1.5 times the weight of fluid lost during exercise (IAAF,2007; Shirreffs et al, 2004; Shireffs et al, 1996). You should not drink all this amount straight away, consume as much as you feel comfortable with, then drink the remainder in divided doses until you are fully hydrated.

During more strenuous exercise in warm or humid conditions such as marathon running, you could be losing as much as 2 litres per hour.