The First-Night Effect and Sex Differences in Strength and Muscular Endurance Performance

Introduction: The first‐night effect, characterized by disturbed sleep in an unfamiliarenvironment, may impair next‐day physical performance. However, whether this responsediffers between men and women remains unclear. This study investigated sex differences inthe effects of sleeping in an unfamiliar environment on strength and muscular endurancein resistance‐trained individuals.Methods: Thirty‐two resistance‐trained participants (16 women, 16 men; 23 ± 4 years)completed a randomized, counterbalanced crossover study involving two conditions:sleeping for 8 h at home or in the laboratory. The following morning, participantsperformed bench press and back squat strength tests across 25‐90%1RM, followed bymuscular endurance tests to failure at 65%1RM.