Delayed muscle soreness and cytoskeletal alterations: an immunocytological study in man.

Delayed muscle soreness in man is known to be attributed to a disorganization of the myofibrils. Our aim in the present study was to investigate whether the intermediate filament system is affected as well. Biopsies were taken from the right m. vastus lateralis of six males (aged 23 +/- 3 years) suffering from severe post-exercise soreness of their thigh muscles. Intermediate filament protein was visualized by indirect immunofluorescence microscopy using an antibody specific to desmin. A typical finding in biopsies taken 3 days after exercise was abundant longitudinal "desmin" extensions. Moreover, strongly autofluorescent granules were observed beneath the sarcolemma. It is concluded that muscles subjected to unusual exercise contain myofibrillar and cytoskeletal disturbances accompanied by increased lysosomal activity.