Time course of serum protein changes after strenuous exercise of the forearm flexors

The time course of changes in serum proteins and other blood constituents after eccentric exercise of the forearm flexors by six nonweight-trained female subjects (age, 19.7 +/- 1.9 years) was investigated. Eccentric muscle actions are those in which the muscle lengthens as it exerts force, as when a person lowers a weight. Serum levels of creatine kinase, lactate dehydrogenase, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, gamma-glutamyl transpeptidase, myoglobin, as well as urea nitrogen, uric acid, creatinine, calcium, and phosphorus were examined before and for 6 days after exercise. Creatine kinase increased dramatically (peak value ranged from 6740 to 24,200 U/L) and aspartate aminotransferase, lactate dehydrogenase, alanine aminotransferase, and myoglobin followed the same time course as creatine kinase, but their peak values were lower. These proteins did not increase significantly until 48 hours after exercise and reached peak values 3 to 5 days after exercise. Alkaline phosphatase, gamma-glutamyl transpeptidase, uric acid, urea nitrogen, creatinine, calcium, and phosphorus showed no change. There is either a delay in muscle protein release by damaged muscle fibers, or the proteins are unable to leave the interstitial area for the 24 to 48 hour period after exercise. Because of the long delay, care should be taken when blood protein levels are interpreted in persons who have exercised strenuously (even if only for a short period of intense effort) several days before any diagnostic tests are performed.