AN AGING-ASSOCIATED DECLINE IN FORCE PRODUCTION AFTER REPETITIVE CONTRACTIONS BY RAT SKINNED SKELETAL-MUSCLE FIBERS

Chemically skinned muscle fibre segments were prepared from the extens or digitorum longus (EDL) and soleus muscles of young (5-6 months) and old (24-31 months) male Wistar rats, Muscle fibres were activated rep etitively with a buffered calcium solution a total of 50 times, and th e force resulting from each activation recorded, Both EDL and soleus f ibres showed a substantial decline in maximum force over the series of 50 contractions. The decline in maximum force was significantly highe r in old EDL and soleus fibres than in their young counterparts, indic ating a difference between the contractile apparatus of skeletal muscl e 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 t he existence of changes to the contractile apparatus with ageing.