CHANGES IN PLASMA ENZYME-ACTIVITIES IN PROFESSIONAL RACING CYCLISTS

Objective-To reports changes in plasma levels in professional racing c yclists.Methods-Plasma levels of the intracellular enzymes aspartate a minotransferase, alanine aminotransferase, gamma glutamyl transpeptida se, lactate dehydrogenase, and alkaline phosphatase were measured rest ing and after exercise in professional cyclists participating in two r oad races: Vuelta Ciclista a Valencia (800 km, beginning of the cyclis t season), and the top rank race Vuelta a Espana (2700 km, at the end of cyclist season). Results-A significant increase in plasma aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase was observed at the end of the race over the corresponding paired star t values (P < 0.05). The increase in plasma lactate dehydrogenase afte r the race was only statistically significant (P < 0.05) in the Vuelta a Espana. The longer the duration of the cycle tour race, the greater were the increases in aspartate aminotransferase and alanine aminotra nsferase levels. The high levels returned to their start values during the overnight resting period. Conclusions-The presence of these enzym es in the blood is probably due to mechanically damaged muscle cells l eaking their contents into the interstitial fluid.