Objective Sedentary Time, MVPA, 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 with physical functional health independent of time spent in moderate-vigorous physical activity (MVPA).

Methods: Community-based men and women (n=8623, 48-92 years 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/s) and timed chair stands speed (TCSS, stands/minute). Of these, 4051 participants wore an accelerometer (GT1M Actigraph) for 7 days to estimate time spent in moderate-vigorous physical activity (MVPA, >=1952 counts/minute) and sedentary (ST, <100 counts/minute). Relationships 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 non-linear associations.

Results: Men in the highest compared to 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/s; 95% CI 8.4, 15.1) and faster TCSS (2.35 stands/minute; 95% CI 1.11, 3.59) after multivariable adjustment. Similarly women in the highest quartile of MVPA were stronger (2.47kg; 95% CI 1.79, 3.14), had faster UWS (15.5cm/s; 95% CI 12.4, 18.6) and faster TCSS (3.27stands/min; 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 (Pinteractions >0.05).

Conclusions: More time spent in MVPA was associated with higher physical capability but there were no independent ST associations.