METABOLIC VERSUS MECHANICAL STRESS IN MUSCLE TISSUE INJURY.

Abstract

816 This study investigated the controversial relationship between the oxidative stress and the occurrence of muscle damage during endurance training. One group of 20 male Wistar rats was submitted to 8 weeks of endurance training in a running treadmill, with increasing effort during the first 4 weeks, when the exercise intensity was then maintained at a constant level. Another 20 animals were the sedentary control group. Every week the concentration of thiobarbituric acid reactive substances (TBARS) was determined in urine and the activities of the enzymes creatine kinase (CK), catalase (CAT) and glutathione reductase (GR) were assayed in blood. Our results showed an increased CK activity in trained animals during the whole training period. A CK activity peak occurred at the second week, as the urinary TBARS concentration was also reaching a maximum value. When the antioxidant defense system activity increased, at the third week, both TBARS and CK levels lowered although this latter was always higher than the values found for the sedentary animals. The high CK levels, even when TBARS concntration was already decreased, suggest that the damage to the muscle occurs through a mechanical rather than oxidative stress. This process could be important to cause the muscle biochemical adaptation to exercise.