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.