ADAPTIVE STRATEGIES OF RESPIRATORY MUSCLES IN RESPONSE TO ENDURANCE EXERCISE

The purpose of this review is to discuss the adaptive strategies of ma mmalian respiratory muscles in response to whole-body endurance exerci se training. It is now clear that endurance training results in small (i.e., 20-30%) but significant increases in mitochondrial enzyme activ ity and the activities of key antioxidant enzymes (i.e., superoxide di smutase and glutathione peroxidase) within the rodent diaphragm. Inter estingly, the magnitude of this training-induced increase in costal di aphragmatic oxidative and antioxidant enzyme activity is relatively in dependent of the exercise duration and intensity. Although the crural diaphragm of rodents is also capable of increasing its oxidative and a ntioxidant capacity in response to endurance training, high- to modera te-intensity. exercise of long duration is required to promote these c hanges. Endurance training also increases the oxidative capacity of ot her key rodent inspiratory muscles, such as the parasternal intercosta ls and external intercostals. Furthermore, endurance training results in small (similar to 10%) increases in the oxidative capacity of key a bdominal (expiratory) muscles. Whether the improvement in oxidative ca pacity of respiratory muscles is of significant magnitude to result in improvement in respiratory muscle performance remains an unanswered q uestion.