Reactive Agility Performance in Older Adults: Associations With Muscle Health and Functional Performance

INTRODUCTION: This study investigated reactive agility performance in older adults and examined its associations with muscle-related and functional factors. METHODS: This cross-sectional study included 114 community-dwelling older adults with 110 valid reactive-agility data. A modified functional reactive agility test (FRAT) provided total time (TT), decision time (DT), and movement time (MT) from each participant's shortest-TT trial. Muscle health was characterized using skeletal muscle index (SMI) and handgrip strength, while functional performance was assessed separately using the five-times sit-to-stand test (5STST). Between-group differences were tested using one-way or Welch analysis of variance as appropriate. Separate multivariable models were fitted for TT, DT, and MT, with multiple-testing correction. RESULTS: Minimum-TT trial outcomes did not differ among the four muscle-health groups. In the multivariable models, slower 5STST performance was consistently associated with longer TT (β = 0.48), DT (β = 0.37), and MT (β = 0.44), with all associations remaining significant after false-discovery-rate correction (all q < 0.001). No other examined covariate remained significantly associated with reactive agility outcomes after multiple-testing correction. Variance decomposition of TT showed that the MT variance term constituted the largest component of between-participant variability (70.2%), compared with the DT variance (10.4%) and DT-MT covariance (19.4%) terms. CONCLUSION: Reactive agility did not differ significantly among muscle-health groups, whereas 5STST performance was consistently associated with TT, DT, and MT. Movement time represented the largest component of between-participant variability in TT, suggesting that functional performance and temporal components may offer complementary information for characterizing reactive agility in older adults.