Abstract / Summary
Abstract To compare post-fatigue landing mechanics, dynamic balance, and knee joint repositioning between men with anterior cruciate ligament reconstruction (ACLR) and dynamic knee valgus (DKV) who underwent a short daytime nap opportunity versus quiet rest before a standardized functional fatigue protocol. An assessor-blinded randomized controlled trial was conducted in 44 men. Participants were allocated to a 30-min daytime nap opportunity or a time- and environment-matched quiet-rest control group using block randomization. After baseline assessment, participants underwent either the nap or quiet-rest intervention, followed by a standardized functional fatigue protocol based on stretch-shortening cycle exercises. Actigraphy-estimated sleep duration during the nap opportunity was 22.8 ± 4.6 min. Landing mechanics, Y-Balance test normalized composite score, and knee joint position sense absolute error (at 30 ∘ and 60 ∘ ) were assessed at baseline) before the nap/quiet-rest intervention (and immediately after the fatigue protocol. Between-group differences in post-fatigue outcomes were analyzed using analysis of covariance (ANCOVA), adjusted for baseline values. Holm–Bonferroni correction was applied for multiple comparisons. The trial was retrospectively registered with the Iranian Registry of Clinical Trials (IRCT20250519065806N4) on 26 June 2026. After adjustment for baseline values, post-fatigue landing-error scores were lower in the nap group than in the quiet-rest group (adjusted mean difference, − 1.39 points (95% CI, − 2.03 to − 0.74); p < 0.001; partial η² = 0.32). Knee joint repositioning error at 60° was also lower in the nap group (adjusted mean difference, − 2.41° (95% CI, − 3.44 to − 1.37); p < 0.001; partial η²= 0.35). No significant between-group differences were observed for Y-Balance test normalized composite score (adjusted mean difference, − 0.79%; 95% CI, − 2.15 to 0.56; p = 0.244; partial η² = 0.03) or repositioning error at 30° (adjusted mean difference, 0.91° (95% CI, − 0.61 to 2.42); p = 0.235; partial η² = 0.03). Post-fatigue landing-error scores and knee joint repositioning error at 60° were lower in participants assigned to the short daytime nap opportunity than in those assigned to quiet rest, whereas no between-group differences were observed for the Y-Balance test normalized composite score or repositioning error at 30°. Because outcomes were not assessed immediately after the nap or quiet-rest period and before the fatigue protocol, these findings do not establish that napping specifically attenuated the response to fatigue. Clinical trial registration: This study was retrospectively registered with the Iranian Registry of Clinical Trials (IRCT) under registration number IRCT20250519065806N4 on 26 June 2026.