Associations of sitting and physical activity with grip strength and balance in mid-life: 1970 British Cohort Study.

Strength and balance training are now recommended in many physical activity (PA) guidelines. However, it is unclear whether these recommendations are applicable to middle-aged adults. We aimed to examine the associations of sitting and physical activity times with grip strength and standing balance performance in mid-life. Up to 4726 participants from the 1970 British Cohort study, with data on sitting and activity (measured using a thigh-worn accelerometer (activPAL3-micro)), grip strength and balance times at age 46 years were included in analyses. Associations of sitting, moderate-vigorous, and total PA times with grip strength and balance performance were tested using linear and multinomial logistic regression models, respectively. Greater time spent sitting was associated with weaker grip strength even after adjustment for potential confounders and MVPA time (fully adjusted regression coefficient: -0.51 kg (95% CI: -0.63, -0.39) per 1-hour sitting/day). Associations of PA time with grip strength were not independent of sitting time. There was only a weak association between sitting time and balance performance but greater MVPA and total PA times were associated with higher relative risks of successfully balancing for 30 seconds with eyes closed (vs poor balance). However, these associations were fully attenuated after adjustments for covariates. In summary, among a sample of middle-aged adults a robust association between sitting time and grip strength was observed. These findings suggest potential benefits of actively promoting less sitting alongside activities that specifically benefit muscle strength and balance performance in mid-life to ensure that people maintain all important aspects of their physical capability as they age.