Physical Activity, Sedentary Time, and Bone Strength From Childhood to Early Adulthood: A Mixed Longitudinal HR-pQCT study

Abstract

Bone strength is influenced by bone geometry, density, and bone microarchitecture, which adapt to increased mechanical loads during growth. Physical activity (PA) is essential for optimal bone strength accrual; however, less is known about how sedentary time influences bone strength and its determinants. Thus, our aim was to investigate the prospective associations between PA, sedentary time, and bone strength and its determinants during adolescence. We used HR-pQCT at distal tibia (8% site) and radius (7% site) in 173 girls and 136 boys (aged 9 to 20 years at baseline). We conducted a maximum of four annual measurements at the tibia (n = 785 observations) and radius (n = 582 observations). We assessed moderate-to-vigorous PA (MVPA) and sedentary time with accelerometers (ActiGraph GT1M). We aligned participants on maturity (years from age at peak height velocity) and fit a mixed-effects model adjusting for maturity, sex, ethnicity, leg muscle power, lean mass, limb length, dietary calcium, and MVPA in sedentary time models. MVPA was a positive independent predictor of bone strength (failure load [F.Load]) and bone volume fraction (BV/TV) at the tibia and radius, total area (Tt.Ar) and cortical porosity (Ct.Po) at the tibia, and negative predictor of load-to-strength ratio at the radius. Sedentary time was a negative independent predictor of Tt.Ar at both sites and Ct.Po at the tibia and a positive predictor of cortical thickness (Ct.Th), trabecular thickness (Tb.Th), and cortical bone mineral density (Ct.BMD) at the tibia. Bone parameters demonstrated maturity-specific associations with MVPA and sedentary time, whereby associations were strongest during early and mid-puberty. Our findings support the importance of PA for bone strength accrual and its determinants across adolescent growth and provide new evidence of a detrimental association of sedentary time with bone geometry but positive associations with microarchitecture. This study highlights maturity-specific relationships of bone strength and its determinants with loading and unloading. Future studies should evaluate the dose-response relationship and whether associations persist into adulthood. © 2017 American Society for Bone and Mineral Research.

The effect of diet and sociopolitical change on physiological stress and behavior in lateRoman‐EarlyByzantine (300–700AD) and Islamic (902–1,235AD) populations from Ibiza, Spain

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Ariketa fisikoa hezur-dentsitate mineralaren suspertzaile

“…Hezur-dentsitate maila maximoa, oro har, hezur-indarraren maila maximoarekin erlazionatzen da [13] (hezurraren masa, dentsitatea, mikroarkitektura, erreparazio-mekanismoak eta geometria-propietateak dira hezur-indarraren adierazle). Hezur-dentsitate mineralaren maila maximoa gaztaroan lortzen da, nerabezaro amaieran, eta guztiz erabakigarria da bizitzan zehar edukiko den hezur-osasunean.…”

Differential skeletal response in adult and aged rats to independent and combinatorial stimulation with pulsed electromagnetic fields and mechanical vibration

“…Bone is a highly mechanosensitive and adaptive system, and increased physiological loads on the skeleton via aerobic or anaerobic exercise can lead to anabolic bone changes and improved bone status. 12,13 In particular, a large body of experimental evidence over the two decades has substantiated that whole-body vibration (WBV) with low intensity (<1 g) and high frequency (≥30 Hz) improves bone quantity and/ or quality in both normal and osteoporotic animals induced with ovariectomy, disuse, or diabetes by triggering anabolic and anti-catabolic bone responses. [14][15][16][17] WBV has also been found to increase bone mineral density (BMD) in young and postmenopausal women, [18][19][20] revealing the potential of WBV serving as a surrogate for strenuous physical exercise.…”