Changes in tissue degradation markers and subjective reports of pain resulting from eccentric muscle contractions

The delayed onset of muscular soreness (DOMS) following a heavy eccentric exercise was studied with the aim to verify the "muscular structure" and the "connective tissue" theories explaining the development of DOMS. The responses of creatine kinase (CK; "structural theory" marker) and hydroxyproline (OHP, "connective tissue theory" marker), as well as level and location of the perceived soreness, were determined following eccentric exercise. Plasma CK activity was elevated 48 and 72 h after the eccentric exercise compared with the pre-exercise values, while OHP concentrations remained unchanged. Examination of pain location reports revealed two groups of responders (distal vs. mid-point muscle pain). Distal pain responders were found to have significantly higher post-exercise CK activity than mid-point pain responders, the OHP levels being alike. These findings are supportive of the "muscular structure" theory for DOMS development. However, the non-uniform location for DOMS pain confounds the overall data interpretation.