Influence Of Rapid Weight Gain On Outcomes In Professional Boxers And Mixed Martial Artists

Abstract

PURPOSE: Professional combat sport athletes commonly practice rapid weight gain (RWG) following official weigh-in to gain a theoretical competitive advantage over their opponent. Recent literature highlights conflicting evidence on the associations between RWG and competitive success. The objective of this study was to evaluate the effect of RWG on competitive success in large cohorts of professional boxers and mixed martial artists. METHODS: Fighter demographic and event records from 2015-2019 for 1582 professional boxers and 752 mixed martial artists were collected from the California State Athletic Commission (CSAC). Official weigh-in weights, event weights, and bout outcomes were recorded. Independent t-tests were used to compare absolute and relative weight gain based on bout outcome for each sport. Logistic regression was used to assess the relationships between bout outcome and predictors including weight gain, competitive level, weight class and year of competition. RESULTS: For boxers, winners gained significantly more absolute and relative weight than losers (4.9 ± 0.1 vs. 4.3 ± 0.1 kg, p < 0.001) and (7.9 ± 0.1 vs. 6.9 ± 0.1 %, p < 0.001), respectively. Logistic regression revealed relative RWG significantly predicted winning outcome (OR = 1.11, 95% CI [1.07, 1.15]). Among mixed martial artists, winners gained significantly more absolute and relative weight than losers (5.9 ± 0.1 vs. 5.3 ± 0.1 kg, p < 0.001) and (8.7 ± 0.2 vs. 7.8 ± 0.2 %, p < 0.001), respectively. Logistic regression revealed relative RWG significantly predicted winning outcome (OR = 1.07, 95% CI [1.03, 1.12]). CONCLUSIONS: Despite previous studies with conflicting findings, this study contributes further evidence that RWG confers a competitive advantage in professional boxing and mixed martial arts.