The purpose of this review is to discuss the adaptive strategies of mammalian respiratory muscles in response to whole-body endurance exercise training. It is now clear that endurance training results in small (i.e., 20-30%) but significant increases in mitochondrial enzyme activity and the activities of key antioxidant enzymes (i.e., superoxide dismutase and glutathione peroxidase) within the rodent diaphragm. Interestingly, the magnitude of this training-induced increase in costal diaphragmatic oxidative and antioxidant enzyme activity is relatively independent of the exercise duration and intensity. Although the crural diaphragm of rodents is also capable of increasing its oxidative and antioxidant capacity in response to endurance training, high- to moderate-intensity exercise of long duration is required to promote these changes. Endurance training also increases the oxidative capacity of other key rodent inspiratory muscles, such as the parasternal intercostals and external intercostals. Furthermore, endurance training results in small (≈10%) increases in the oxidative capacity of key abdominal (expiratory) muscles. Whether the improvement in oxidative capacity of respiratory muscles is of significant magnitude to result in improvement in respiratory muscle performance remains an unanswered question.
Center for Exercise Science and Departments of Exercise and Sport Sciences and Physiology, University of Florida, Gainesville, FL 32611
Submitted for publication August 1995.
Accepted for publication October 1995.
The authors thank Louise Fletcher and Jeff Coombes for their editorial comments on this manuscript. This work was supported by the American Lung Association-Florida.
Address for correspondence: Scott K. Powers, Center for Exercise Science, Room 33, University of Florida, Gainesville, FL 32611.