Dehydration and Acute Weight Gain in Mixed Martial Arts Fighters Prior to Competition

The purpose of the investigation was to characterize the magnitude of dehydration and rapid weight gain (RWG) in mixed martial arts (MMA) fighters prior competition. Hydration status and body mass were determined ~24 h prior and the again ~ 2 h prior to competition in 40 MMA fighters (Mean ? SE, age: 26 ? 1 yr, height: 1.77 ? 0.01 m, body mass: 75.8 ? 1.5 kg). RWG was defined as the amount of body weight the fighters gained in the ~22 h period between the official weight-in and competition. On average, the fighters gained 3.40 ? 2.18 kg or 4.4% of their body mass in the ~ 22 h period prior to competition. Urine specific gravity (Usg) significantly decreased (P < 0.001) from 1.028 ? 0.001 to 1.020 ? 0.001 g/ml during the rehydration period. 39% of fighters presented a Usg of greater than 1.021 g/ml ~2 h prior competition indicating dehydration. In conclusion, fighters undergo significant dehydration and fluctuation in body mass in the 24 h period prior to competition. Hydration status indicates that a significant proportion (39%) of fighters are competing in a dehydrated state. Weight management guidelines in MMA are warranted.