Recently, in my Advanced Exercise Physiology class, I was given the assignment of writing a paper about the effectiveness of hydration on both the prevention of heat illnesses, as well as improvements in physical performance. As I went through the relevant literature, I quickly noticed that there seemed to be dozens – if not hundreds – of papers published about how hydration can prevent mild and severe heat illnesses, ranging from simple dehydration to heat exhaustion and heat stroke.
Finding information about the effects of optimal hydration on athletic and sports performance was a bit more difficult, but some pretty clear evidence does exist. For example, Walsh et. al. (1994) demonstrated the performance benefits associated with remaining fully hydrated during exercise. They had subjects cycle for one hour at 70% of VO2 peak before exercising to exhaustion at 90% of VO2 peak, a task that required about 6-10 minutes to complete. When the subjects were allowed to dehydrate by only 1.8% of their body weight, they lasted slightly more than six minutes before becoming fatigued. When they remained fully hydrated by ingesting fluid at regular intervals throughout the hour of steady-state cycling, they were able to cycle for almost 10 minutes, a large and significant improvement in performance.
Similar effects have been seen with studies done on competitive runners. Casa et. al. (2010) examined physiological and performance variables among trail distance runners when running in the heat. Their study measured these variables among 2 groups of elite trail distance runners during both a sub-maximal and maximal race trial in the heat. One group of runners was well hydrated, and the other was dehydrated, during both the sub-maximal and maximal trials. The results of the study demonstrated decreased body mass and body water loss, lower core body temperature, better running economy, and faster running times over time trials, in hydrated distance runners versus dehydrated distance runners. The researchers surmised that “even a small decrement in hydration status impaired physiologic function and performance while trail running in the heat.”
The “take-home” message for soccer coaches and fitness coaches is that proper hydration will not only prevent heat illness, but it will also allow players to maximize their physical performance. Improvements in running economy, as well as in aerobic and anaerobic endurance, should translate directly into better soccer performance on the pitch.
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