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Background: The hyperbolic torque-duration curve depicts critical torque (CT) and W prime (W′), with the curve's asymptote representing CT as the boundary between heavy- and severe-intensity domains. W′, the curvature constant, indicates cumulative work beyond CT. This study investigated age-related reductions in W′, CT, and gait speed, and whether W′ and CT predict gait speed independently of muscle torque. Methods: three groups (adults, middle-aged, older) totaling 131 women were studied. W′ and CT were determined using 60 maximal isometric voluntary contractions of knee extensors. The fast gait speed was calculated in walking tests at 10 m, 400 m, and six minutes (6 MWT). Results: gait speed decreased (p < 0.05) with age, as did W′ and CT. Both W′ and CT correlated positively with gait speed at different distances (10 m, 400 m, 6 MWT). Adjusted for maximum muscle torque, only W′ maintained a positive association (p < 0.05) with all gait speed tests (10 m: β = 0.201, SE = 0.086; 400 m: β = 0.262, SE = 0.085; 6 MWT: β = 0.187, SE = 0.086). Conclusions: aging led to declines in W′, CT, and gait speed. W′, not CT, remained a significant predictor of gait speed, indicating its importance for older women's mobility. [ABSTRACT FROM AUTHOR]

Background: This study sought to investigate whether different physical function tests (objective measures of physical performance) may identify a low physical resilience in breast cancer survivors (BCS). Methods: This analytical cross-sectional study evaluated 146 BCS and 69 age-matched women without breast cancer history. The different times after the end of treatment were used as criteria for group division. Participants were divided into four groups: control (CT: n = 69–women without breast cancer history); <1.0 years after the end of treatment (<1 YAT: n = 60); 1–3.9 years after the end of treatment (1–3.9 YAT: n = 45); and ≥4 years after the end of treatment (>4 YAT: n = 41). Physical function was evaluated by 4 m walk test (4-MWT), five-times-sit-to-stand test (FTSST), timed up and go test (TUG), and short physical performance battery (SPPB). Age, menopausal status, smoking, number of medications, level of physical activity, body mass index, and muscle strength were used as confounding variables in ANCOVA. Results: All groups that underwent cancer treatment (<1 YAT, 1–3.9 YAT and ≥4 YAT) had lower physical performance (p < 0.001) identified by 4 MWT, TUG, and FTSST when compared to the CT group. For the SPPB, the <1 YAT and ≥4 YAT groups had lower performance (p = 0.005) when compared to the CT. Conclusions: The different physical function tests can be used to identify a low physical resilience in BCS. [ABSTRACT FROM AUTHOR]