Reactance as a possible predictor of better rehydration strategy of combat sport athletes
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Abstract
Rapid weight loss is a widespread practice in combat sports, intended to meet weight-class requirements while preserving an anatomical advantage. These strategies primarily reduce extracellular and intracellular fluid volumes by manipulating carbohydrate, sodium, and water intake, followed by rapid weight gain after the official weigh-in. This study analysed the association between raw bioelectrical impedance variables measured immediately after weigh-in and competitive outcome in amateur combat athletes. A cross-sectional analytical design was conducted with 54 athletes from boxing, Mixed Martial Arts, and Muay Thai. Measurements of resistance (R), reactance (Xc), and phase angle (PhA) were obtained under standardized conditions using a tetrapolar device. Descriptive statistics characterized the sample, and logistic regression evaluated predictors of winning or losing. Mean values for R/H (height), Xc/H, PhA/H, and Z/H reflected a dehydrated profile consistent with recent weight cutting. Only Xc/H met the regression model's entry criteria. Higher Xc/H values were associated with lower odds of winning (OR = 0.857), suggesting that athletes with lower post-weigh-in reactance/height — potentially reflecting more effective rehydration and extracellular volume restoration — were more likely to achieve victory. These findings highlight the physiological relevance of bioelectrical markers for assessing recovery and their promise as indicators of competitive readiness in combat sports.
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