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Intensity of physical activity linked to musculoskeletal health in middle-aged women
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In middle-aged women, moderate to vigorous physical activity is more important for musculoskeletal health than light physical activity or sedentary time, according to findings from a cross-sectional study.
“Each additional 100 [accelerometer counts per minute] of total physical activity was associated with 1.6% greater [femoral neck bone mineral density], 3% greater [lower limb muscle strength] and 1.5% shorter [timed up-and-go test] time,” Feitong Wu, a PhD student at the Menzies Institute for Medical Research at the University of Tasmania in Australia, and colleagues wrote. “Intensity of physical activity was also important: [Moderate to vigorous physical activity] was beneficially associated with [femoral neck] BMD, [lower limb muscle strength], [timed up-and-go test] and [step test], but light physical activity was not associated with any outcomes.”
Wu and colleagues analyzed day from 309 women aged 36 to 57 years who participated in a randomized controlled trial for osteoporosis interventions initiated in 2000. Included participants underwent BMD measurements of the lumber spine and femoral neck via DXA at baseline, 2 years and 12 years, and had at least 5 valid days of physical activity recorded with an accelerometer at 12 years. Women also completed four clinical tests for functional mobility and balance: the timed up-and-go test, step test, functional reach test and lateral reach test, and underwent lower muscle strength measurements via dynamometer. Researchers used linear regression analysis to measure associations between total physical activity, time spent sedentary and in light physical activity, as well as moderate to vigorous physical activity (minutes per day) with each outcome, adjusted for menopausal status, calcium intake, serum 25-hydroxyvitamin D levels and fracture history.
Within the cohort, mean total sedentary time and time spent in moderate to vigorous physical activity were 535 minutes per day and 37 minutes per day, respectively.
After adjustment, researchers found that total physical activity was beneficially associated with femoral neck BMD (beta = 0.011 g/cm²; 95% CI, 0.003-0.019), lower limb muscle strength (beta = 2.13 kg; 95% CI, 0.21-4.06), and the timed up-and-go test for functional mobility (beta = –0.08 seconds; 95% CI, –0.129 to –0.03).
Moderate to vigorous physical activity was also associated with femoral neck BMD (beta = 0.005 g/cm²; 95% CI, 0.0007-0.0094), lower limb muscle strength (beta = 1.48 kg; 95% CI, 0.45-2.52), and both the step test (beta = 0.12 steps; 95% CI, 0.02-0.23) and timed up-and-go test for functional mobility (beta = –0.043 seconds; 95% CI, –0.07 to –0.016). After additional adjustment for sedentary time, the associations between femoral neck BMD and moderate to vigorous physical activity and the timed up-and-go test were attenuated, whereas the association with lower limb muscle strength was strengthened (beta = 1.45 kg; 95% CI, 0.42-2.48), as was association with the step test (beta = 0.15 steps; 95% CI, 0.04-0.27).
Researchers found no associations between light physical activity and musculoskeletal health parameters.
“Importantly, associations of [moderate to vigorous physical activity] with [lower leg muscle strength], [timed up-and-go test] and [step test], but not [femoral neck] BMD were independent of sedentary time, but not vice versa,” the researchers wrote. “However, there were no interactions between [moderate to vigorous physical activity] and sedentary time. These findings suggest that greater total physical activity is important for musculoskeletal health in middle-aged women, but increasing time spent in [moderate to vigorous physical activity] may be more important than decreasing sedentary time or increasing light physical activity.” – by Regina Schaffer
Disclosure: The researchers report no relevant financial disclosures.
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