More Support For Ad Libitum Drinking

As it is in the sports world, in the military world the old standard of drinking to completely offset sweat loss (as determined by weight loss) during exercise is being replaced by a new hydration strategy of drinking according to thirst. A new military study published in Medicine & Science in Sports & Exercise provides further evidence in support of the effectiveness of ad libitum fluid intake during exercise. Fifteen soldiers drank water according to their thirst throughout a four-hour march. On average they drank 383 mL per hour, or only 61% as much fluid as they lost through sweat. As a result, the men lost 1.0 kg of weight on average. Despite this, post-exercise testing revealed that their core body temperature, blood osmolality, sodium concentration, and total body water were well maintained. These findings suggest that thirst is a better guide than weight loss to the true fluid needs of exercising individuals.