Search

Abstract: Background context: There are differing views as to the causes of disc degeneration. One view, referred to as a cumulative or repetitive injury model, explains disc degeneration, in great part, as the result of “wear and tear” on the disc from routine daily exposures to physical loading or biomechanical forces. Perhaps paradoxically, such physical loading has been thought to be generally beneficial for other structures of the musculoskeletal system. Purpose: The goal of this study was to investigate the associations of physical loading from body weight using quantitative measures of disc degeneration. Study design: This is an exposure-discordant twin study. Methods: We selected 44 pairs of healthy male monozygotic (MZ) twins with 8 kg or more discordance in body weight (mean 13 kg), with lumbar magnetic resonance imaging and bone density measurements available. The main outcome of disc degeneration was assessed through quantitatively measured disc height, and disc signal intensity and signal variation adjusted by the intrabody reference, adjacent cerebrospinal fluid signal, at L1–L4. Data on suspected constitutional and environmental risk factors were available for control of possible confounding factors. Results: Higher body weight was associated with 6.2% higher bone density in the lumbar spine, confirming an effective discordance (p<.0001). Disc signal variation was 5.4% higher (“better”) among the heavier MZ co-twins (p=.005), but the 2.6% higher disc heights and 2.9% higher adjusted disc signals were not statistically significant. Conclusions: Contrary to common beliefs, our findings suggest that cumulative or repetitive loading because of higher body mass (nearly 30 pounds on average) was not harmful to the discs. In fact, a slight delay in L1–L4 disc desiccation was observed in the heavier men, as compared with their lighter twin brothers. [Copyright &y& Elsevier]

Abstract: Introduction: We studied whether vigorous physical activity in young adulthood is associated with higher femoral bone density and lower risk of hip fracture at older age in men. Materials: A cohort of former male elite athletes (n =2147) and matched control subjects (n = 1467) were studied for their leisure physical activity, and for fragility fractures at the hip (proximal femur) by Cox regression. Areal bone mineral densities (aBMD) at femoral neck and trochanter region were measured using dual-energy X-ray absorptiometry in a subgroup of the former athletes (n = 87; median age 59 years) and in a population-based control group (n = 194) and compared by general linear models. Results: After their active sporting careers, the former athletes participated in leisure physical activity more than the matched control subjects (p <0.0001). The hazard ratio (HR) of osteoporotic hip fracture adjusted for the occupational group was 0.77 (95% CI 0.45 to 1.32, p =0.34) in the athletes compared with the control subjects. The mean age at the time of the fracture event was 76.9 years (95% CI 73.2 to 78.8) for the athletes and 70.6 years (95% CI 67.1 to 72.9) for the matched control subjects (p = 0.005). Adjusted for age and body mass index, aBMD at the proximal femur was significantly higher in the former athletes compared with the population-based control group (p < 0.0001 for both measurement sites). Conclusions: Osteoporotic hip fractures were sustained at a significantly older age among former athletes compared with control subjects. Clear skeletal benefits of long-term physical loading were also observed in comparative DXA measurements of aBMD. [Copyright &y& Elsevier]