Changes in the contractile material of human skeletal muscle following tendinous injury.

The most marked changes in the human muscle following tendinous injury can be observed in the contractile components. There is a widening of the Z-membrane, dispersion of the sarcomers, a break in their continuity, and detached bundles of myofibrils are found in the sarcoplasm. A change occurs also in the proportion of different fibre types of the muscles, in the muscle with tendinous injury a predominance of type II fibre becoming apparent. Among the proteins of myofibrils a product of disintegration of a molecular weight of 31 000 can be consequently demonstrated, and in some muscles products of disintegration with a molecular weight between 90 000 and 58,000 arise.