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Context: Visceral adipose tissue (VAT) has been recognized to be a metabolically active fat depot that may have paracrine effects on surrounding tissues, including muscle. Since many adults accumulate VAT as they age, the effect of changes in VAT on muscle is of interest. Objective: We determined the association between 6-year changes in VAT and paraspinal muscle density, an indicator of fatty infiltration. Methods: This study included 1145 participants from the Framingham Study third-generation cohort who had both quantitative computed tomography scans of the spine at baseline and 6-year's follow-up, on whom muscle density was measured along with VAT. We implemented multiple regression to determine the association of muscle density at follow-up as primary outcome measure with changes in VAT (follow-up minus baseline divided by 100), adjusting for VAT at baseline, age, sex, height, menopausal status, presence of diabetes, and physical activity. Analyses were performed in men and women separately. Results: After adjustment for covariates, individuals with the greatest accumulation of VAT over 6 years had significantly lower paraspinal density at the follow-up with an estimated 0.302 (95% CI, -0.380 to -0.224) and 0.476 (95% CI: -0.598 to -0.354) lower muscle density (HU) per 100-cm³ increase in VAT (both P values<.001) in men and women, respectively. Conclusion: These results highlight that age-related accumulation of VAT in men and women is associated with lower muscle density. VAT may represent a modifiable risk factor for poor musculoskeletal outcomes with aging. [ABSTRACT FROM AUTHOR]

Vertebral fractures (VFx) are common among older adults. Epidemiological studies report high occurrence of VFx at mid‐thoracic and thoracolumbar regions of the spine; however, reasons for this observation remain poorly understood. Prior reports of high ratios of spinal loading to vertebral strength in the thoracolumbar region suggest a possible biomechanical explanation. However, no studies have evaluated load‐to‐strength ratios (LSRs) throughout the spine for a large number of activities in a sizeable cohort. Thus, we performed a cross‐sectional study in a sample of adult men and women from a population‐based cohort to: 1) determine which activities cause the largest vertebral LSRs, and 2) examine patterns of LSRs along the spine for these high‐load activities. We used subject‐specific musculoskeletal models of the trunk to determine vertebral compressive loads for 109 activities in 250 individuals (aged 41 to 90 years, 50% women) from the Framingham Heart Study. Vertebral compressive strengths from T4 to L4 were calculated from computed tomography–based vertebral size and bone density measurements. We determined which activities caused maximum LSRs at each of these spinal levels. We identified nine activities that accounted for >95% of the maximum LSRs overall and at least 89.6% at each spinal level. The activity with the highest LSR varied by spinal level, and three distinct spinal regions could be identified by the activity producing maximum LSRs: lateral bending with a weight in one hand (upper thoracic), holding weights with elbows flexed (lower thoracic), and forward flexion with weight (lumbar). This study highlights the need to consider a range of lifting, holding, and non‐symmetric activities when evaluating vertebral LSRs. Moreover, we identified key activities that produce higher loading in multiple regions of the spine. These results provide the first guidance on what activities to consider when evaluating vertebral load‐to‐strength ratios in future studies, including those examining dynamic motions and the biomechanics of VFx. © 2020 American Society for Bone and Mineral Research (ASBMR). [ABSTRACT FROM AUTHOR]

Background: Cross-sectional studies suggest that trunk muscle morphology in the lumbar spine is an important determinant of kyphosis severity in older adults. The contribution of age-related changes in muscle morphology in the thoracic and lumbar spine to progression of kyphosis is not known. Our objective was to determine cross-sectional and longitudinal associations of thoracic and lumbar muscle size and density with kyphosis.Methods: Participants were 1,087 women and men (mean age: 61 years) of the Framingham Heart Study who underwent baseline and follow-up quantitative computed tomography (QCT) scanning 6 years apart. We used QCT scans to measure trunk muscle cross-sectional area (CSA, cm2) and density (HU) at the thoracic and lumbar spine and Cobb angle (degrees) from T4 to T12. Linear regression models estimated the association between muscle morphology and kyphosis.Results: At baseline, smaller muscle CSA and lower density of thoracic (but not lumbar) spine muscles were associated with a larger (worse) Cobb angle in women and men. For example, each standard deviation decrease in baseline thoracic paraspinal muscle CSA was associated with a larger baseline Cobb angle in women (3.7 degrees, 95% CI: 2.9, 4.5) and men (2.5 degrees, 95% CI: 1.6, 3.3). Longitudinal analyses showed that loss of muscle CSA and density at the thoracic and lumbar spine was not associated with progression of kyphosis.Conclusions: Our findings suggest that kyphosis severity is related to smaller and lower density trunk muscles at the thoracic spine. Future studies are needed to determine how strengthening mid-back musculature alters muscle properties and contributes to preventing kyphosis progression. [ABSTRACT FROM AUTHOR]

Background: Deficits in balance and muscle function are important risk factors for falls in older adults. Aging is associated with significant declines in muscle size and density, but associations of trunk muscle size and density with balance and falls in older adults have not been previously examined.Methods: Trunk muscle size (cross-sectional area) and attenuation (a measure of tissue density) were measured in computed tomography scans (at the L2 lumbar level) in a cohort of older adults (mean ± SD age of 81.9±6.4) residing in independent living communities. Outcome measures were postural sway measured during quiet standing and Short Physical Performance Battery (SPPB) at baseline, and falls reported by participants for up to 3 years after baseline measurements.Results: Higher muscle density was associated with reduced postural sway, particularly sway velocities, in both men and women, and better Short Physical Performance Battery score in women, but was not associated with falls. Larger muscle size was associated with increased postural sway in men and women and with increased likelihood of falling in men.Conclusions: The results suggest that balance depends more on muscle quality than on the size of the muscle. The unexpected finding that larger muscle size was associated with increased postural sway and increased fall risk requires further investigation, but highlights the importance of factors besides muscle size in muscle function in older adults. [ABSTRACT FROM AUTHOR]