An ageing-associated decline in force production after repetitive contractions by rat skinned skeletal muscle fibres

Chemically skinned muscle fibre segments were prepared from the extensor digitorum longus (EDL) and soleus muscles of young (5-6 months) and old (24-31 months) male Wistar rats, Muscle fibres were activated repetitively with a buffered calcium solution a total of 50 times, and the force resulting from each activation recorded, Both EDL and soleus fibres showed a substantial decline in maximum force over the series of 50 contractions. The decline in maximum force was significantly higher in old EDL and soleus fibres than in their young counterparts, indicating a difference between the contractile apparatus of skeletal muscle from young and old animals, Normalized tension, defined as force per muscle fibre cross-sectional area, was significantly lower in fibres from the old animals than from the young, giving further evidence of the existence of changes to the contractile apparatus with ageing.