Key result
Maximal Ca2+ activated specific force in skeletal muscle fibres from elderly women aged 66-90 years was significantly lower by 20% compared to historical data from young adults.
Why the study?
The study investigated calcium and strontium activation properties of skeletal muscle fibres from elderly women to better understand contractile changes with aging.
Cross-Sectional (n=7)
Skeletal muscle fibres from elderly women show qualitative and quantitative changes in contractile activation properties, including a 20% reduction in maximal Ca2+ activated specific force compared to adults, which may explain age-related mobility changes.
May contribute to age-related weakness in women; leaves open human translation and therapeutic targets.
The single freshly skinned muscle fibre technique was used to investigate Ca 2+ - and Sr 2+ -activation properties of skeletal muscle fibres from elderly women (66–90 years). Muscle biopsies were obtained from the vastus lateralis muscle. Three populations of muscle fibres were identified according to their specific Sr 2+ -activation properties: slow-twitch (type I), fast-twitch (type II) and hybrid (type I/II) fibres. All three fibre types were sampled from the biopsies of 66 to 72 years old women, but the muscle biopsies of women older than 80 years yielded only slow-twitch (type I) fibres. The proportion of hybrid fibres in the vastus lateralis muscle of women of circa 70 years of age (24%) was several-fold greater than in the same muscle of adults (< 10%), suggesting that muscle remodelling occurs around this age. There were no differences between the Ca 2+ - and Sr 2+ -activation properties of slow-twitch fibres from the two groups of elderly women, but there were differences compared with muscle fibres from young adults with respect to sensitivity to Ca 2+ , steepness of the activation curves, and characteristics of the fibre-type dependent phenomenon of spontaneous oscillatory contractions (SPOC) (or force oscillations) occurring at submaximal levels of activation. The maximal Ca 2+ activated specific force from all the fibres collected from the seven old women use in the present study was significantly lower by 20% than in the same muscle of adults. Taken together these results show there are qualitative and quantitative changes in the activation properties of the contractile apparatus of muscle fibres from the vastus lateralis muscle of women with advancing age, and that these changes need to be considered when explaining observed changes in women’s mobility with aging.
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Ronaldson et al. (2022) conducted a cross-sectional in Healthy aging (undergoing orthopaedic surgery) (n=7). Advancing age vs. Young adults (historical data) was evaluated on Maximal Ca2+ activated specific force. Maximal Ca2+ activated specific force in skeletal muscle fibres from elderly women aged 66-90 years was significantly lower by 20% compared to historical data from young adults.
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