Time watching television or videos and strenuous physical activity in younger women either independently or interact to predict lower limb muscle strength and balance but not bone density in midlife: a 12-yr prospective study — ASN Events
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Time watching television or videos and strenuous physical activity in younger women either independently or interact to predict lower limb muscle strength and balance but not bone density in midlife: a 12-yr prospective study (#123)

Feitong Wu 1 , Graeme Jones 1 , Tania Winzenberg 1 2
  1. Menzies Institute for Medical Research, University of Tasmania, Hobart, TAS, Australia
  2. Faculty of Health, University of Tasmania, Hobart

58aa4d5fe2aaf-Figure+1.tifBackground: The effects of sedentary behaviours and physical activity on musculoskeletal health remain unclear in younger adults.

Aim: To describe independent associations and interactions of time spent watching television or videos (TTV) and strenuous physical activity (SPA) in younger women with bone mineral density (BMD), lower limb muscle strength (LMS) and balance in midlife.

Methods: Ten-year follow-up of a 2-yr osteoporosis education randomized controlled trial among 470 women aged 25-44 years. Associations of self-reported TTV and SPA at baseline with BMD at femoral neck and lumbar spine, LMS and balance (timed up and go test (TUG), step test (ST), functional reach test (FRT) and lateral reach test (LRT)) measured after 12 years were examined using linear regression.

Results: After adjusted for confounders, including SPA, TTV was detrimentally associated with LMS (β=-6.8, 95%confidence interval (CI) -12.6 to -1.1 and -3.8, -12.8 to 5.1 for 2-3 and ≥ 3 hours, respectively, vs. ≤1 hours) and TUG (β=0.11, 95%CI -0.04 to 0.26 and 0.17, -0.06 to 0.40)but not the FRT. Conversely, SPA was beneficially associated with LMS (β= 10.1, 3.9 to 16.3 for≥5 days, respectively, vs. <2 days), TUG (-0.17, -0.34 to -0.01) and FRT (1.53, -0.05 to 3.12). There were interactions between TTV and SPA for ST and LRT; the beneficial effect of lower TTV were greater in those undertaking higher levels of SPA (Figure 1, p=0.03 for ST and 0.06 for LRT). Neither TTV nor SPA was associated with BMD.

Conclusions: Both TTV and SPA in younger women independently predicted LMS and TUG, and had synergistic effects to predict ST and LRT. This suggests there could be greater benefits from both reducing TTV and increasing SPA in younger age for preventing reduced muscle strength and balance in later life than from addressing either sedentary behaviour or physical activity in isolation.