The effects of hypohydration on muscular performance and markers of catabolism in females.

Abstract

The purpose of this study was to determine the effects of previous night dehydration on muscular strength, endurance, and lower-body power, perceptual measures, and markers of catabolism in resistance-trained females. Ten healthy, resistance-trained females completed two bouts of resistance exercise, either dehydrated (~3% body weight) (DT) or heat exposed with fluid replacement (HT). Each exercise bout consisted of one rep maximum (1RM) followed by five sets to failure of 75% of 1RM for bench press and leg press, and vertical jump assessment. Muscle and blood samples were obtained prior to and 1hr following exercise. Blood samples were obtained to examine cortisol. From each muscle sample, glucocorticoid receptor-DNA (GR-DNA) binding and mRNA expression were determined. Bench press 1RM (p = 0.04) was significantly lower for DT compared to HT. No significant difference was found for leg press 1RM. There was no difference in total reps completed for bench press or leg press. No significant differences were found for total volume lifted for bench press or leg press or vertical jump. There were no significant interactions between session and time for any markers of mRNA expression. There was no significant interaction or main effects for session and time for serum cortisol. There was a significant main effect for session for GR- DNA binding (p = 043). GR-DNA binding was significantly elevated post exercise for DT (p = .016). Current results suggest that hypohydration may have a negative impact on bench press 1RM performance. Though the only performance measure to reach a statistically significant difference was bench press 1RM, there was a reduction in leg press 1RM and total volume lifted for both bench press and leg press. While this was an acute bout of only two exercises, it would be reasonable to suggest that this reduction in volume would continue for other exercises across a full workout. Additionally, GR-DNA binding was increased with hypohydration. Theoretically, if an individual were to be chronically hypohydrated, this reduction in volume and increase in GR-DNA binding could diminish the anabolic response to resistance exercise and potentially lead to muscle atrophy.