Respiratory muscle reserve in rats during heavy exercise

Luc E. Gosselin, David Megirian, Joshua Rodman, Donna Mueller, and Gaspar A. Farkas Department of Physical Therapy, Exercise, and Nutrition Sciences, State University of New York at Buffalo, Buffalo, New York 14214 Received 10 April 1997; accepted in final form 23 July 1997. Gosselin, Luc E., David Megirian, Joshua Rodman, Donna Mueller, and Gaspar A. Farkas. Respiratory muscle reserve in rats during heavy exercise. J. Appl. Physiol. 83(4): 1405-1409, 1997. The extent to which the respiratory pump muscles limit maximal aerobic capacity in quadrupeds is not entirely clear. To examine the effect of reduced respiratory muscle reserve on aerobic capacity, whole body peak oxygen consumption ( O 2 peak ) was measured in healthy Sprague-Dawley rats before and after Sham, unilateral, or bilateral hemidiaphragm denervation (Dnv) surgery. O 2 peak was determined by using a graded treadmill running test. Hemidiaphragm paralysis was verified after testing by recording the absence of electromyographic activity during inspiration. Before surgery, O 2 peak averaged 86, 87, and 92 ml · kg 1 · min 1 for the Sham, unilateral, and bilateral Dnv groups, respectively. Two weeks after surgery, there was no significant change in O 2 peak for either the Sham or unilateral Dnv group. However, O 2 peak decreased ~19% in the bilateral Dnv group 2 wk after surgery. These findings strongly suggest that the pulmonary system in rats is designed such that during heavy exercise, the remaining respiratory pump muscles are able to compensate for the loss of one hemidiaphragm, but not of both. hemiparalysis; diaphragm; denervation; peak oxygen consumption 0161-7567/97 $5.00 Copyright © 1997 the American Physiological Society