Effect of rapid weight loss incorporating hot salt water immersion on changes in body mass, blood markers, and indices of performance in male mixed martial arts athletes

Purpose To investigate the effects of rapid weight loss (RWL), incorporating comparison of hot water immersion (HWI) in fresh or salt water, on changes in body mass, blood markers, and indices of performance in mixed martial arts athletes. Methods In a crossover design comparing fresh water (FWB) to salt water (SWB; 5.0%wt/vol Epsom salt) bathing, 13 males performed 20 min of HWI (similar to 40.3 degrees C) followed by 40 min wrapped in a heated blanket, twice in sequence (2 h total). Before bathing, similar to 26 to similar to 28 h of fluid and dietary restriction was undertaken, and similar to 24 to similar to 26 h of a high carbohydrate diet and rehydration was undertaken as recovery. Results During the entire RWL process, participants lost similar to 5.3% body mass. Body mass lost during the 2 h hot bath protocol was 2.17 +/- 0.81 kg (similar to 2.7% body mass) and 2.24 +/- 0.64 kg (similar to 2.8% body mass) for FWB and SWB, respectively (P = 0.647 between trials). Blood urea nitrogen, creatinine, sodium, chloride, hemoglobin, and hematocrit were increased (all P < 0.05), and plasma volume was decreased (similar to 14%; P < 0.01), but did not differ between FWB and SWB, and were similar to baseline values after recovery. No indices of performance (e.g., countermovement jump, isometric strength, and functional threshold power) were impacted when RWL was followed by the recovery process. Conclusion Under the conditions of this hot bath protocol, fluid loss was not augmented by the addition of similar to 5.0%wt/vol of Epsom salt during HWI, and RWL of similar to 5.3% body mass followed by >24 h of recovery did not impact indices of performance.

Automated summary

This study investigated the effects of rapid weight loss on mixed martial arts athletes. The results showed that adding Epsom salt to hot water immersion did not increase fluid loss, and the recovery period after weight loss did not impact performance indices.