title: Differences in respiratory muscle activity during cycling and walking do not influence dyspnea perception in obese patients with COPD.
abstract: In patients with combined obesity and chronic obstructive pulmonary disease (COPD), dyspnea intensity at matched work rates during weight-supported cycling and weight-bearing walking is similar, despite consistent metabolic differences between test modalities. The present study examined the influence of differences in activity of the diaphragm and abdominal muscles during cycling and walking on intensity and quality of dyspnea at matched ventilation in obese patients with COPD. We compared respiratory muscle activity patterns and dyspnea ratings during incremental cycle and treadmill exercise tests, where work rate was matched, in 12 obese (body mass index 36.6 ± 5.4 kg/m(2); mean ± SD) patients with moderate COPD. We used a multipair electrode-balloon catheter to compare electromyography of the diaphragm and esophageal, gastric, and transdiaphragmatic pressures during the two exercise tests. Ventilation, breathing pattern, operating lung volumes, global respiratory effort, and electrical activation of the diaphragm were similar across exercise modalities for a given work rate. The cycling position was associated with greater neuromuscular efficiency of the diaphragm (P < 0.01), greater diaphragm use (P < 0.01) measured by the ventilatory muscle recruitment index, and less expiratory muscle activity compared (P < 0.01) with treadmill walking. However, intensity and quality of dyspnea were similar between exercise modalities. In obese patients with COPD, altered respiratory muscle activity due to body position differences between cycling and walking did not modulate perceived dyspnea when indirect measures of respiratory neural drive were unchanged.
authors.affiliation: Respiratory Investigation Unit, Department of Medicine, Queen's University & Kingston General Hospital, Kingston, Ontario, Canada;
authors.forename: Casey E
authors.initials: CE
authors.lastname: Ciavaglia
authors.affiliation: Respiratory Investigation Unit, Department of Medicine, Queen's University & Kingston General Hospital, Kingston, Ontario, Canada; Department of Physical Therapy and UBC Centre for Heart Lung Innovation, University of British Columbia, Vancouver, British Columbia, Canada; and.
authors.forename: Jordan A
authors.initials: JA
authors.lastname: Guenette
authors.affiliation: Respiratory Investigation Unit, Department of Medicine, Queen's University & Kingston General Hospital, Kingston, Ontario, Canada; Rehabilitation Sciences, KU Leuven, Leuven, Belgium.
authors.forename: Daniel
authors.initials: D
authors.lastname: Langer
authors.affiliation: Respiratory Investigation Unit, Department of Medicine, Queen's University & Kingston General Hospital, Kingston, Ontario, Canada;
authors.forename: Katherine A
authors.initials: KA
authors.lastname: Webb
authors.affiliation: Respiratory Investigation Unit, Department of Medicine, Queen's University & Kingston General Hospital, Kingston, Ontario, Canada;
authors.forename: J
authors.initials: J
authors.lastname: Alberto Neder
authors.affiliation: Respiratory Investigation Unit, Department of Medicine, Queen's University & Kingston General Hospital, Kingston, Ontario, Canada; odonnell@queensu.ca.
authors.forename: Denis E
authors.initials: DE
authors.lastname: O'Donnell
mesh_terms: D000368:Aged; D001642:Bicycling / Q000502:physiology; D003430:Cross-Sectional Studies; D004417:Dyspnea / Q000209:etiology* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications* / Q000503:physiopathology; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications* / Q000503:physiopathology; D012132:Respiratory Muscles / Q000503:physiopathology*; D016138:Walking / Q000502:physiology
keywords: COPD; dyspnea; exercise modality; obesity; respiratory mechanics