Challenges of Endurance Exercise: Hydration and Electrolyte Balance

In human and equine athletes, loss of body fluid in sweat during prolonged exercise exceeds voluntary fluid replacement. This leads to a condition that has been termed involuntary dehydration. The magnitude of dehydration can be estimated by measuring body mass loss during the endurance event. This body mass loss usually persists for hours to days in the recovery period and water and electrolyte deficits are usually not fully replaced until one or more meals have been consumed following the exercise bout. Unfortunately, loss of body water and electrolytes can contribute to development of several medical or “metabolic” problems either during the exercise bout or even after successful completion. Dehydration has long been considered the most important risk factor for development of medical problems in endurance athletes. However, other factors, including a decrease in circulating volume and autonomic dysregulation leading to compromised tissue perfusion, have recently been suggested to be equally important risk factors. […]