The current study shows, for the first time, that diaphragmatic and expiratory
muscle activity is different during cycling and walking in obese individuals with COPD.
However, despite the relatively reduced neuromuscular efficiency of the diaphragm
during weight-bearing treadmill exercise compared with weight-supported cycling,
perceived respiratory discomfort was not increased. Our results further indicate that
exertional dyspnea intensity is ultimately dictated by the amplitude of respiratory neural
drive. Moreover, under conditions where respiratory neural drive and the volume and
timing components of breathing were constant, body position-related alterations in
activity of major respiratory muscles during different exercise modalities had no
measurable effects on the intensity and quality of dyspnea.