Abstract
BackgroundIn humans, ageing causes skeletal muscles to become atrophied, weak, and easily fatigued. In rodent studies, ageing has been associated with significant muscle atrophy and changes in the contractile properties of the muscles. However, it is not entirely clear whether these changes in contractile properties can occur before there is significant atrophy, and whether males and females are affected differently.Methods and ResultsWe investigated various contractile properties of whole isolated fast-twitch EDL muscles from adult (2–6 months-old) and aged (12–22 months-old) male and female mice. Atrophy was not present in the aged mice. Compared with adult mice, EDL muscles of aged mice had significantly lower specific force, longer tetanus relaxation times, and lower fatiguability. In the properties of absolute force and muscle relaxation times, females were affected by ageing to a greater extent than males. Additionally, EDL muscles from a separate group of male mice were subjected to eccentric contractions of 15% strain, and larger force deficits were found in aged than in adult mice.ConclusionOur findings provide further insight into the muscle atrophy, weakness and fatiguability experienced by the elderly. We have shown that even in the absence of muscle atrophy, there are definite alterations in the physiological properties of whole fast-twitch muscle from ageing mice, and for some of these properties the alterations are more pronounced in female mice than in male mice.
Highlights
Ageing in humans is accompanied by diminished function of the musculoskeletal system [1]
We have shown that even in the absence of muscle atrophy, there are definite alterations in the physiological properties of whole fast-twitch muscle from ageing mice, and for some of these properties the alterations are more pronounced in female mice than in male mice
Eccentric contractions and muscle stiffness In a separate group of mice, we examined the susceptibility of extensor digitorum longus (EDL) muscles to damage from a mild eccentric contraction protocol of 15% strain
Summary
Ageing in humans is accompanied by diminished function of the musculoskeletal system [1]. Between the ages of 40 and 80 years, muscle mass declines by 30 to 50% in both men and women [2] This is accompanied by a decrease in muscle strength [3,4], an increase in fatiguability [5], and an increase in the susceptibility to contraction-induced damage [2]. In vitro preparations of whole isolated muscle remove the influence of neural factors, so that age-related changes can be attributed to changes within the muscle tissue itself. They allow more accurate quantitation of parameters such as muscle mass and cross-sectional area than can be achieved in human studies. It is not entirely clear whether these changes in contractile properties can occur before there is significant atrophy, and whether males and females are affected differently
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