Abstract
Physical activity is considered crucial in attenuating losses in strength and power associated with ageing. However, in well-functioning, active older adults the relationship between habitual physical activity and muscle function is surprisingly unclear. Leg press velocity, force, and power, were compared between 50 older and 30 younger healthy individuals, and associations with habitual physical activity explored. An incremental power test was performed on a pneumatic leg press, with theoretical maximum velocity, force, and power calculated. Vastus lateralis muscle thickness was measured by ultrasound, and participants wore a combined accelerometer and heart rate monitor for 6-days of free-living. Older individuals produced lower absolute maximum velocity, force, and power, than younger individuals. When accounting for smaller muscle size, older individual’s maximum force and power remained markedly lower. Both groups were active, however using age specific thresholds for classifying physical activity, the older individuals engaged in twice the amount of moderate-to-vigorous physical activity in comparison to the younger individuals. There were no associations between any characteristics of muscle function and physical activity. These data support that the ability to generate force and power deteriorates with age, however habitual physical activity levels do not explain inter-individual differences in muscle function in active older individuals.
Highlights
Ageing is associated with decreasing skeletal muscle mass at a rate of around 0.5–1% per year after the age of 50 years, with concomitant loss of muscle force generating capability [1]
When Fmax and Pmax were considered relative to vastus lateralis (VL) muscle thickness, Fmax:VL was significantly lower in older individuals compared to younger individuals (60.1 (15.2) N/mm vs. 71.8 (14.7) N/mm, P < 0.01, g = 0.51), as was Pmax:VL (22.4 (8.3) W/mm vs. 36.2 (10.3) W/mm, P < 0.01, g = 0.93)
Physical activity level (PAL) was significantly lower in older compared to younger individuals (1.59 (0.17) vs. 1.74 (0.23), P < 0.01, g = 0.77)
Summary
Ageing is associated with decreasing skeletal muscle mass at a rate of around 0.5–1% per year after the age of 50 years, with concomitant loss of muscle force generating capability [1]. This loss of muscle mass (sarcopenia) and strength (dynapenia), in the lower limb, are regarded as central causes of functional decline and subsequent loss of independence in older adults [2, 3]. Strength, and power, in older adults rate that would be expected based on muscle mass loss [6]. Accurate and safe measurement of peak power in older adults is challenging due to safety and technique related issues, use of pneumatic resistance exercise machines instrumented to record kinetic data has emerged as an accurate, valid and reliable tool to assess lower limb muscle power [12]
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