Oliver Barley, in conjunction with others, has previously authored studies showing MMA athletes cut more weight than other combat sports athletes, and that even mild weight cuts affect performance, has recently released a new study purporting to show that physical factors are not behind some or all of the decreased endurance performance after rehydration.
The study tested the performance of athletes after dehydrating them by roughly 3% of their body weight and allowing three hours of rehydration. It also tested the performance of the same athletes in a control condition at another time. Various measures of hydration, like urine specific gravity, urine osmolality, blood osmolality, etc were also taken.
The study used several markers to measure neuromuscular performance, including measuring muscle contraction and stimulation directly via surface electromyography, and found that while maximal effort wasn’t impacted by dehydration, endurance performance and perception of fatigue was.
The study also shows that athletes following their own rehydration program may not be fully rehydrating themselves; the average weight following rehydration was slightly lower than the weight prior to dehydration and urine markers for hydration still indicated dehydration.
The ad-libitum nature of the rehydration process allows the study to better reflect the reality of performance for the individuals tested, and likely the reality for the majority of individuals competing, but it does make some of the findings difficult to rely on. It’s difficult to separate how much of the performance decline three hours after rehydration was due to residual dehydration still having effects when participants weren’t fully rehydrated by some measures.
The biggest difference between participants in the control and dehydrated/rehydrated conditions came in the mood testing. The average scores for tension, depression, anger, fatigue and confusion were all markedly and significantly raised immediately following dehydration, and perception of fatigue remained significantly higher even after reyhdration.
Functional cognitive testing showed no significant differences between the control condition and the rehydrated condition.
The study is a solid piece of work and illustrates a few things: Firstly, that there’s a good chance many combat sports athletes aren’t adequately rehydrating themselves, even after mild dehydration, and secondly that it’s possible that some, perhaps even much, of the performance decrease we see after dehydration & rehydration is due to an athlete’s perception of how tired they are, rather than any physiological response.
You can read the full study here, and listen to an interview with one of the study authors, Oliver Barley, on the Wonder Twins Power Podcast here.