Bias varies for bioimpedance analysis and skinfold technique when stratifying collegiate male athletes' fat-free mass hydration levels.

This study evaluated the accuracy of bioimpedance analysis (BIA)- and skinfold (SF)-based body fat percentage estimates in collegiate athletes with varying fat-free mass (FFM) hydration levels. Subjects were evaluated as a whole (n = 63) and at FFM hydration levels of 64.00%-68.99% (FFM-HydrationL1; n = 37) and 69.00%-74.00% (FFM-HydrationL2; n = 26). Proportional bias was absent in the SF technique when stratifying FFM hydration levels. Contrarily, proportional bias was observed when using BIA for FFM-HydrationL1, but not in FFM-HydrationL2. Novelty Fat-free mass hydration levels impact BIA-based body fat estimates more than skinfold-based body fat.