Vincent O Onywera
26 November 2007
opinion
Nairobi — Can you play, exercise or compete at your best if you are dehydrated? The answer is no. The body usually loses water during exercise primarily through sweat.
This happens even during cold weather or when swimming. As we get older, drinking enough water is especially important because with age our body is less able to regulate our temperature and thus putting us at an increased risk of heat-related illness.
Age also affects our ability to stay hydrated during exercise and our ability to recognise when we need more water. Adequate fluid replacement helps maintain hydration and, therefore, promotes the health, safety and optimal physical performance of individuals participating in regular physical activity.
Disturbances in body water and electrolyte balance can adversely affect cellular as well as systemic function, subsequently reducing the ability of humans to tolerate prolonged exercise.
Water lost during exercise - induced sweating - can lead to dehydration of both intracellular and extracellular fluid compartments of the body. Even a small amount of dehydration (one per cent body weight) can increase cardiovascular strain as indicated by a disproportionate elevation of heart rate during exercise.
This limits the ability of the body to transfer heat from contracting muscles to the skin surface where heat can be dissipated to the environment. Therefore, consequences of body water deficits can increase the probability for impairing exercise performance and developing heat related complications such as heat exhaustion, among others.
It is important to note that dehydration can impair physiological function which eventually can lead to injury, aggression, lack of concentration, poor game plan, fatigue, frustration, among others. The end result of is impaired exercise performance. To maintain proper fluid balance during exercise, the following are recommended:
Aim to start training sessions or competition well hydrated (a clear or light-coloured urine is a good indicator of adequate hydration).
Drink small amounts at regular intervals during exercise. Use breaks in the game or training to take on additional fluids. Increase fluid intake in hot and humid conditions.
After exercise, replace 1.5 litres of fluid for every kilogramme of body weight lost.
Avoid caffeine and alcohol when rehydrating as they promote fluid loss.
The addition of sodium (0.5-0.7g/L) and carbohydrate (4 per cent concentration) to drinks improves absorption by the body and promotes glycogen replenishment. Additional sodium may be necessary for endurance events and for individuals who are "salty" sweaters.
Note that plain water is appropriate for exercise events lasting less than one hour. Drink before you get thirsty - thirst is an indication that you were dehydrated 24 hours ago. So you must always try not to get thirsty. In fact keep drinking even after your thirst is quenched
During exercise, humans typically drink insufficient volumes of fluid to offset sweat losses. This observation is referred to as "voluntary dehydration". To avoid or delay the detrimental effects of dehydration during exercise, individuals appear to benefit from fluid ingested prior to competition.
Dr Onywera is a Lecturer at Kenyatta University, Department of Exercise, Recreation and Sport Science.
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