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Associations between physical activity and time spent sedentary and musculoskeletal outcomes remain unclear in middle-aged adults. This study aimed to describe associations between objectively-measured physical activity and sedentary time and musculoskeletal health outcomes in middle-aged women. This cross-sectional study from a population-based sample of 309 women (age 36 to 57 years) examined associations of total physical activity (accelerometer counts/min of wear time), and time spent sedentary, in light physical activities and moderate-to-vigorous physical activities (MVPA) (by Actigraph GT1M accelerometer) with lumbar spine (LS) and femoral neck (FN) bone mineral density (BMD) (by dual-energy X-ray absorptiometry), lower limb muscle strength (LMS), and functional mobility and balance tests (timed up and go test [TUG], functional reach test [FRT], lateral reach test [LRT], and step test [ST]) using linear regression. Total physical activity was beneficially associated with FN BMD (values are β; 95% CI) (0.011 g/cm² ; 95% CI, 0.003 to 0.019 g/cm² ), LMS (2.13 kg; 95% CI, 0.21 to 4.06 kg), and TUG (-0.080 s; 95% CI, -0.129 to -0.030 s), after adjustment for confounders. MVPA was also beneficially associated with FN BMD (0.0050 g/cm² ; 95% CI, 0.0007 to 0.0094 g/cm² ), LMS (1.48 kg; 95% CI, 0.45 to 2.52 kg), ST (0.12 steps; 95% CI, 0.02 to 0.23 steps), and TUG (-0.043 s; 95% CI, -0.070 to -0.016 s). Associations between MVPA and LMS, TUG and ST persisted after further adjustment for sedentary time. Only TUG was associated with sedentary time, with a detrimental effect (0.075 s; 95% CI, 0.013 to 0.137 s) and this did not persist after further adjustment for MVPA. Light physical activity was not associated with any outcome. MVPA appears more important than light physical activity or sedentary time for many musculoskeletal outcomes in middle-aged women. This needs to be considered when developing interventions to improve habitual physical activity that aim to improve musculoskeletal health.

Item Type:	Refereed Article
Keywords:	Physical activity, bone density, muscle strength, balance, middle-aged women
Research Division:	Biomedical and Clinical Sciences
Research Group:	Clinical sciences
Research Field:	Rheumatology and arthritis
Objective Division:	Health
Objective Group:	Clinical health
Objective Field:	Clinical health not elsewhere classified
UTAS Author:	Wu, F (Dr Feitong Wu)
UTAS Author:	Wills, K (Dr Karen Wills)
UTAS Author:	Laslett, LL (Dr Laura Laslett)
UTAS Author:	Jones, G (Professor Graeme Jones)
UTAS Author:	Winzenberg, T (Professor Tania Winzenberg)
ID Code:	112989
Year Published:	2017 (online first 2016)
Web of Science® Times Cited:	27
Deposited By:	Menzies Institute for Medical Research
Deposited On:	2016-12-07
Last Modified:	2018-03-19
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