Influence of variations in body hydration on cognitive function: Effect of hyperhydration, heat stress, and exercise-induced dehydration

Eight healthy men, unacclimated to heat, were submitted to variations in body hydration. The subjects were kept euhydrated, dehydrated by controlled passive hyperthermia or exercise on a treadmill up to a weight loss of 2.8%, or hyperhydrated using a solution containing glycerol, with a total ingested volume equal to 21.4 ml/kg of body weight, On completion of a 90-min recovery period, the subjects were assigned a pedaling exercise on an arm-crank; ergometer. Psychological tests were administered 30 min after the phase of hydration Variation and 15 min after the arm crank exercise. Both dehydration conditions impaired cognitive abilities (i.e., perceptive discrimination, psyche-motor skills, and short-term memory) as well as subjective estimates nf fatigue, without any relevant differences between them. Short-term memory was significantly greater following hyperhydration when compared to euhydration (P < .05). Following arm crank exercise, further effects of dehydration were found for tracking performance only (P < .05). Moreover, long-term memory was impaired in both control and dehydration situations, whereas then was no decrement in performance in the hyperhydration condition.