Independent Associations of Stroke and Sarcopenia-Related Phenotype with Lower-Limb Strength and Gait: A 1:2 Matched Cohort Analysis

Background/Objectives: Whether stroke and sarcopenia relate to the same components of lower-limb function is unclear. We estimated each exposure’s mutually adjusted association with strength, gait performance, and gait variability, and their interaction. Methods: Thirty-three stroke survivors were matched 1:2 to 66 controls (n = 99) and classified into operational sarcopenia-related phenotype groups by AWGS 2019 muscle-mass and gait-speed cut-offs, not diagnoses. Strength, spatiotemporal gait, and gait variability were analysed in rank-based additive MANCOVAs (Pillai’s trace; permutation within matched sets; Holm correction across domains). Further runs added gait speed, removed the phenotype, added weight, or substituted ASM/Ht2. Results: Stroke was associated with strength (Pillai’s V = 0.240, Holm p = 0.003) and gait variability (V = 0.096, Holm p = 0.044; not significant after adjustment for weight), but not with gait performance (Holm p = 0.133) unless the phenotype was removed (V = 0.194, Holm p < 0.001). The phenotype was associated with all three domains (Holm p ≤ 0.008) through its slow-gait group; the low-ASM group and ASM/Ht2 showed no associations. At a given gait speed, neither exposure was associated with gait (Holm p ≥ 0.247). Several judgements varied across matched datasets. Conclusions: In this cohort, lower-limb function followed strength and walking performance more closely than muscle mass. The stroke association with strength held across matched datasets and limb rules, and neither exposure’s gait association was detectable at a given walking speed. No interaction was detected, and the estimates are imprecise, particularly for strength. These are conditional cross-sectional associations.