Haptoglobin and serum enzymatic response to maximal exercise in relation to physical fitness.

This study investigated the potential value of specific cellular responses to acute and chronic exercise as indices of physical fitness. Muscle enzymatic and hemolytic responses following a progressive cycle-ergometer test to maximal aerobic capacity were studied in 12 women and 12 men, aged 27 to 55 yr, who had been previously assigned to "high" and "low" fitness groups. Venous blood samples were obtained at rest prior to the cycle test, immediately following maximal effort, and 1, 2, 4, 6 and 24 h post exercise. The samples were analyzed for hematocrit (Hct), hemoglobin (Hb), lactate dehydrogenase (LDH), serum glutamic oxalacetic transaminase (SGOT), creatine phosphokinase (CK), CK isoenzymes, and haptoglobin (Hapt). Hemoglobin and Hct were the only variables to rise significantly (P less than 0.05) following exercise, and at all sampling times were significantly lower in the women compared with the men; CK was constituted in the MM isoenzyme band at all times; and Hapt levels were significantly lower in high-fitness men and women as compared with low-fitness men and women. These results indicate that one progressive test to maximal aerobic capacity is not sufficient to induce significant muscle enzymatic or hemolytic stress responses. They do suggest, however, that a chronic hemolytic condition exists as a result of aerobic conditioning activity.