Objective Sedentary Time, Moderate-to-Vigorous Physical Activity, and Physical Capability in a British Cohort

Purpose Sedentariness has been proposed as an independent risk factor for poor health. However, few studies have considered associations of sedentary time (ST) with physical functional health independent of time spent in moderate-to-vigorous physical activity (MVPA). Methods Community-based men and women (n = 8623, 48-92 yr old) in the European Prospective Investigation of Cancer-Norfolk study attended a health examination for objective measurement of physical capability, including grip strength (Smedley dynamometer (kg)), usual walking speed (UWS (cm center dot s(-1))), and timed chair stand speed (TCSS (stands per minute)). Of these, 4051 participants wore an accelerometer (GT1M ActiGraph) for 7 d to estimate time spent in MVPA (MVPA, >= 1952 counts per minute) and ST (ST, <100 counts per minute). Relations between physical capability outcomes and both MVPA and ST were explored using linear regression. The mutual independence of associations was also tested, and ST-MVPA interactions were explored using fractional polynomial models to account for nonlinear associations. Results Men in the highest compared with those in the lowest sex-specific quartile of MVPA were stronger (1.84 kg; 95% confidence interval (CI), 0.79-2.89), had faster UWS (11.7 cm center dot s(-1); 95% CI, 8.4-15.1) and faster TCSS (2.35 stands per minute; 95% CI, 1.11-3.59) after multivariable adjustment. Similarly, women in the highest quartile of MVPA were stronger (2.47 kg; 95% CI, 1.79-3.14) and had faster UWS (15.5 cm center dot s(-1); 95% CI, 12.4-18.6) and faster TCSS (3.27 stands per minute; 95% CI, 2.19-4.25). Associations persisted after further adjustment for ST. Associations between higher ST and lower physical capability were also observed, but these were attenuated after accounting for MVPA. Furthermore, no MVPA-ST interactions were observed (P-interactions > 0.05). Conclusions More time spent in MVPA was associated with higher physical capability, but there were no independent ST associations.