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Structural and functional determinants of skeletal muscle weakness

WP-2 focused on one of the aspects of age induced frailty, i.e. muscle weakness, and analysed its possible causes at cellular and molecular level. In more detail the WP aimed to assess whether muscle weakness is due to:
- A shift in fibre type composition and/or a selective fibre atrophy (slow fibres develop less force and much less power than fast fibres);

- A decrease in myofibrillar protein content of muscle fibres that exceeds the decrease in CSA determining a decline in myofibrillar protein density:

- A change in functional properties of muscle fibres;

- The impact of training on single muscle fibre properties in the elderly.

The research work has clarified that:
- Fibre type composition in elderly subjects is significantly affected by the level of activity going through a shift towards fast fibres in sedentary elderly subjects and towards slow fibres in active elderly subjects;

- In elderly subjects a loss of contractility, namely a decrease in force and velocity, occurs in single muscle fibres independently from a change in myosin isoform (fibre type) due both to a loss of myosin, the motor of contraction, in the fibres and to a change in the function of the myosin molecule itself;

- A long duration training at moderate intensity is able to increase both force and velocity of muscle fibres independently from a change in fibre type both in young and elderly subjects and is therefore able to counteract the effect of ageing on structure and function of muscle fibres.

Related information

Result In Brief

Reported by

University of Pavia
Dipartimento di Medicina Sperimentale, Via Forlanini 6
27100 Pavia
Italy
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