It has long been established that both short and long-term exercise increase metabolic rate and heat production. This naturally predisposes participants to dehydration. Typical symptoms of dehydration include elevated temperature, fluid and electrolyte imbalance due to sweating, and loss of critical nutrients, such as glycogen (depleted via metabolic pathways). Many individuals participating in moderate to rigorous training schedules may engage in daily exercise, if not multiple exercise routines in one day (3,4,5,6). It then follows that the goal for these individuals should be avoidance of dehydration and maximization of rehydration through maintenance of electrolyte balance, replenishment of muscle glycogen, and plasma osmolality. Thus, examination of a fluid’s efficacy in these three areas is crucial. Through extensive research, it is evident that Gatorade will rehydrate faster and more effectively than water.
Vital to maintenance of homeostasis is the regulation of plasma osmolality. The Renin-Angiotensin-Aldosterone system, which works to regulate blood pressure, plays a crucial role in fluid balance. When dehydration occurs, blood osmolality increases, which stimulates the release of antidiuretic hormone (ADH), ultimately leading to increased water reabsorption. This leads to more concentrated urine, and less concentrated plasma. Low plasma osmolality works in the opposite fashion: ADH release is inhibited, water reabsorption decreases, and urine is less concentrated. The added electrolytes and carbohydrates in Gatorade would facilitate greater fluid retention through stimulation of renin and vasopressin, increasing urinary sodium reabsorption (3). Studies of both urine volume and plasma volume changes are effective methods for evaluating the effectiveness of Gatorade as opposed to water.
The importance of the inclusion of sodium for regulation of plasma osmolality was prevalent in many studies. According to Shirreffs et al. drinking water after exercise created a decrease in plasma osmolality in addition to sodium levels. This led to increased urine production coupled with a reduction in desire to drink, exacerbating dehydration and delaying rehydration. If left with low electrolyte concentrations, the amount of urine excreted will leave athletes in negative fluid balance, and decrease the rate of rehydration. Additionally, some studies have suggested that fluid retention is inversely related to the sodium levels present in the fluid (1,5). Evidence strongly supports the addition of sodium to the ingested beverage, as sodium lost through sweat is greater than potassium (5).
In a study comparing efficacies of Evian mineral water, San Benedetto mineral water, and Apfelschorle apple juice, athletes who drank a volume equal to 150% of their lost body-mass were observed to be in a lower hydrated state compared to their pre-test measurements; however, subjects who drank Gatorade were closer to their hydrated pre-test...