Impact of Dehydration on Performance

By 21 October 2013Latest, Nutrition

This week we have a Guest Blogger in the form of Richard Marques from Richard has worked with us, at Bodyline, for many years now and in this post he looks at the effect of dehydration on exercise performance…….


Exercise, even moderate, can result in the loss of fluid through sweat. Dehydration follows soon thereafter should fluids not be replaced during or shortly after training. In addition to impact on your training, this can also affect your health.

As muscles are activated during exercise, additional heat is produced, believed to be + – 75% of energy exerted during exercise. Exercise results in the body’s temperature rising however as your inner bodily temperature has to remain within 37-38 degrees celcius additional heat is dissipated, to prevent heat stroke. Sweating is the bodies main means of dispersing heat, (water from the body is carried through to the skin via blood capillaries), and the quantity of sweat produced / volume of fluid lost is as a result of –

Rate of exercise
Length of exercise
Individual body make-up
Temperature and humidity of environment

An average person could lose up to 1 litre of fluid during an hour of exercise, which could increase with changes to the intensity of exercise or training under more strenuous circumstances, Eg. (temp.; duration; routine; etc…). The individual’s make-up and fitness levels will impact upon the rate at which he/ she sweats.

Richard working with one of his clients at Bodyline

Richard working with one of his clients at Bodyline

Dangers of dehydration

Initially as the body approaches a state of excessive fluid loss; general performance both physical and mental will be impaired. More seriously is the effect on one’s state of health, (et al., 1995; McConnell et al., 1997) – Volume of blood decreases and body temperature increases resulting in strain on the heart, lungs and circulatory system through having to work harder to get blood transported around the body.

Losing as little as 2% in body weight of fluids can result in inability to exercise efficiently; feeling nauseous; vomiting and diarrhoea. Further loss can result in more serious consequences (Montain & Coyle, 1992) –

3% loss = Impaired performance
4% loss = Muscle work capacity declines by up to 80-90%
5% loss = Heat exhaustion
7% loss = Hallucinations
9-10% loss = Circulatory collapse

Hydration requirements

In order to ensure that you perform and are not going to be disadvantaged it is essential to hydrate appropriately prior to undertaking any exercise or competitive event. An effective and simple means of checking your hydration levels is to monitor the colour of your urine, (look for urine to be clear or the colour of pale straw. as the colour gets darker , this generally implies the extent of dehydration).

As important is it to be hydrated, this is not to say you can’t consume too much and become intoxicated. Listen to your body and also signals it sends. Consuming large volumes of water or sports / energy drinks pre, during and post events will not benefit you, in fact to the contrary may affect you more because the body will naturally secrete excess fluids, resulting you making more pit stops and possibly also suffering abdominal cramps.

Richard can be contacted for any advice on health and fitness  on 07851 056020 or via email or you can follow his twitter feed @RichardMarque20









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