Blood indices of muscle injury associated with eccentric muscle contractions.

Serum muscle enzyme activities of eight healthy men (22-32 years old) were measured before and 48 h after separate bouts of repetitive concentric, eccentric, and isometric contractions of the lower leg anterior compartments. Serum creatine kinase and glutamic oxaloacetic acid transaminase levels were both elevated 2 days after the eccentric exercise regimen, exclusively (36 and 17%, respectively). Lactic dehydrogenase levels were not affected by any of the protocols. Delayed muscle soreness was exclusively reported from the eccentrically exercised limb. We suggest that the high tensions developed during eccentric exercise cause mechanical damage, possibly including sarcolemmal degeneration. Subsequently, muscle enzymes are released to the blood. We conclude that postexercise serum levels of some muscle enzymes, at the time of maximal soreness, are qualitative markers of muscle damage.