Title: Association between accelerometer-measured physical activity and muscle capacity in middle-aged postmenopausal women
Authors: Straight, C. Christie, L. Ward-Ritacco, L. et al.
Journal: Menopause
Date: 2015
Impact Factor: 2.8
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Why they did it?
Population ageing is predicted to be one of Australia’s major economic and social challenges of the 21st century. In 2007, 13% of Australians were aged 65+ years, by 2056 this is expected to almost double to 24%. A consequence of ageing is that it leads to a loss of ability to perform activities of daily living (ADL). Common ADLs include walking 1km, lifting or carrying weighted items (e.g. shopping bags) or rising in and out of a chair. The loss of ability to perform ADLs can have debilitating effects on one’s quality of life and has been linked to increased risk of anxiety and depression. A loss of muscle strength and power are key factors in decline of the ability to perform ADLs. Maintaining regular habitual physical activity is considered a key factor for preventing the loss of muscle strength and power. The aim of this study was to identify the relationship between daily physical activity patterns and muscle strength and power.
How they did it?
Sixty postmenopausal women (mean [SD] age, 58.9 [3.9] yrs) participated in this experimental study. At the beginning of the study, each participant wore an accelerometer for a 7-day period. Accelerometers are movement monitors that are worn of the waist and can objectively measure daily step count and the intensity (how hard) and duration of physical activity. After 7 days, participants returned to the laboratory to undergo tests to determine their muscle strength and power, including assessments of the strength and power of the quadriceps muscle group (the muscles used in knee extension). Assessments were also taken for confounding factors such as body mass, body fat percentage and existence of current health conditions (e.g. arthritis, osteoporosis, asthma and diabetes)
What they found?
The findings indicated that there was a significant relationship between the number of steps taken and muscle strength and power. Importantly, this relationship remained after taking into account potential confounding factors such as age, body mass/fat and existing health conditions. A further analysis showed that independent of overall step count, the intensity of the activity mattered. When compared to those who engaged in at least 30 minutes of moderate-intensity physical activity per day (e.g. brisk walking), those who did not, had much lower levels of muscle strength/power.
Ok, what does this mean to me?
This study showed that among older women, regular physical activity is necessary for leg muscle strength and power. Maintaining leg muscle condition is important because this allows older adults to remain active and perform ADLs. Clients who train older adults should encourage regular movement and when safe, engage in some moderate-intensity activity.