Supplementary file 1_Effects of rehydration and nutritional recovery strategies after rapid weight loss on body mass recovery, hydration status, and performance in combat sports athletes: a systematic review and meta-analysis.docx

Pooled post-weigh-in body-mass regain was 6.23% of body mass (95% CI 3.74–8.71; k = 11; n = 1504; I² = 99.2%) and 3.71 kg (95% CI 2.45–4.96; k = 12; n = 1451; I² = 98.9%). In five matched cohorts with paired pre-weigh-in and follow-up measurements, RWL was 8.33% of body mass (95% CI 6.17–10.49; n = 179), followed by a median regain of 106.5% of the preceding loss (range 63.2–154.1%). At official weigh-in, pooled mean urine specific gravity (USG) was 1.029 (95% CI 1.025–1.033; k = 3; n = 58; I² = 92.7%).

Urine osmolality was reported in seven studies and plasma osmolality in four, but these data were not sufficiently comparable for pooling. Twenty-three performance records from 12 studies were too heterogeneous for meta-analysis. No specific nutritional or rehydration approach had sufficiently homogeneous comparative evidence for a strategy-effect meta-analysis.</p>Conclusion<p>Combat-sport athletes commonly regain substantial body mass after weigh-in, but body-mass regain should not be interpreted as complete rehydration or restored performance readiness.

Current strategy-specific evidence is insufficient to identify a superior recovery protocol; standardized, adequately powered trials using multidimensional recovery outcomes are needed.</p>Systematic review registration<p>identifier: CRD420261438676.</p>