It is well known that physical activity causes water and electrolyte losses. A loss in fluid during exercise can impact on performance causing discomfort and dehydration. However, it is important to be aware that fluid gain during exercise can also compromise performance by creating discomfort, excess weight gain and hyponaturemia (dangerously low levels of sodium in the body), placing the athlete at severe health risk. It is therefore vital that sports trainers and athletes are educated on appropriate methods of hydration.
Dehydration causes several physiological concerns for the athlete including a marked change in core temperature (over heating), an increase in heart rate and an an increase in perceived exertion during exercise. This being so, the greater the fluid deficit in the body, the greater the strain on the body during exercise. This is concerning when we consider that during exercise, in temperate-warm-hot-environments, we tend to lose approximately 2 percent of our body weight. A loss of 2 percent body weight hinders an atletes aerobic performance and cognition. Hence, dehydration will only further degrade physical performance and mental abilty. Despite, dehydration being a concern during exercise, it is suggested that dehydration of 3 to 5 percent will not impact on strength or anaerobic performance. Hence, it is of little surprise to find out that overhydration can hinder the performance of athletes in jumping and sprint events.
Water loss during exercise occurs via our respiration, through our gastrointestinal and renal systems and through our sweat. Sweating is the primary avenue for water loss during exercise-heat stress. Moreover, the amount of sweat can vary considerably depending on the physical demands of the activity and environment. For this reason, different sports have unique demands on the body's natural cooling system. For example, some events or training sessions require athletes to perform at higher intensities or longer durations. Moreover, unifroms, gear and protective equipment promote excessive sweating. Given the fregoing variables it is understandable that sweat losses during exercise can range from 0.2 L/h to 3.5 L/h. This being so, it is imperative for sports trainers and athletes to understand and anticipate fluid losses in a specific event in order to calculate an athletes required fluid amount. This can be achieved by weighing an athlete for several days leading up to competition or during training, to establish an accurate baseline, healthy weight. In preparation for an event or training session athletes and trainers should be aware of the following:
1. The personal sweat loss of an individual athlete.
2. Know the expected climate and gear in a specific location.
3. Aim for several days of heat acclimatisation prior to an event.
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