Bone Abstracts

The combined effect of lifestyle physical activity (PA) and sedentary behavioral practices on musculoskeletal health in growing populations is still poorly understood.

Objectives: To investigate the combined influence of mechanical loading of weight-bearing PA (WBPA) and screen-based sedentary practice (SSR) on musculoskeletal profiles among 455 adolescents aged 12–19 years.

Methods: Validated PA and SSR behaviour assessments were used to determine daily physical activities and sedentary practices, respectively. Bone mass of total body (TB), lumbar spine (LS) and proximal femur (PF) was assessed using dual energy X-ray absorptiometry, while muscular strength of the upper and lower extremity were determined using handgrip and isokinetic dynamometers respectively.

Results: Four groups of combined influence of the WBPA and SSR were i) High_WBPALow_SSR, ii) High_WBPAHigh_SSR, iii) Low_WBPALow_SSR and iv) Low_WBPAHigh_SSR. Multivariate analysis model showed that adolescents with high SSR and low WBPA had significantly lower size-adjusted bone mineral content (BMC) of the LS and PF (all, P<0.01) and TB bone area (TBBA) (P<0.001), muscular strength of the handgrip (P<0.001) and hamstring (P<0.01) than those at high WBPA and low SSR group, after adjusting for body size, pubertal growth status, socio-demographic and calcium intakes. Furthermore, participants with higher levels of WBPA and SSR practices had significantly higher size-adjusted PFBMC (P<0.01) and TBBA (P<0.01) compared to those adolescents engaged only in high SSR levels.

Conclusion: These findings suggest that adolescents with higher participation of daily WBPA and low SSR practices exert positive impact on bone mass and muscular strengths than those involved only in high sedentary practice. Effective strategies to promote active lifestyle practices should be emphasised in children and adolescents in order to maximise bone mass accretion and muscular strength during these growing years.

Declaration of interest: This study was funded by University Science Malaysia Research University (RU grant: 1001/PPSK/812015).