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A novel lower limb resistance training program to reduce dyspnea in patients with chronic obstructive pulmonary disease

University of British Columbia

Background: Skeletal muscle disuse, dysfunction and atrophy are important extrapulmonary complications of COPD that contribute to exercise intolerance and increase the intensity of dyspnea through enhanced stimulation of type III/IV muscle afferents. As such, performing aerobic exercise training as part of pulmonary rehabilitation (PR) is difficult because patients are often unable to tolerate the intensity and/or volume of exercise required to achieve clinically important benefits. Resistance training (RT) is an attractive exercise modality as it improves skeletal muscle strength and efficiency and is often more tolerable initially. However, whether individualized RT can reduce dyspnea, leg fatigue, and enhance exercise tolerance in patients with COPD has not been studied. Methods: For this single-armed efficacy study, eight non-smoking patients with COPD (FEV₁/FVC<0.7, 30%<FEV₁<70%) underwent pulmonary function and cardiopulmonary exercise testing. Dyspnea and exercise time were assessed during constant load cycling at 75%Wmax and leg fatigue was measured using electrical stimulation of the quadriceps. After baseline testing, a novel individualized lower limb RT program was performed 3x/week for 4 weeks. Constant load cycling and leg fatigue measurements were repeated upon completion of the intervention. Results: Dyspnea was not significantly reduced during the constant load test to exhaustion (p=0.051), but the mean reduction was of clinical relevance as dyspnea at an exercise isotime was reduced by 2.0 Borg units which is a minimal clinically important difference. Exercise time was significantly increased by 227 s (356 pre vs 583 post, p=0.02). There was a significant reduction in end-expiratory and end-inspiratory lung volumes (p<0.05) and an increase in inspiratory reserve volume and inspiratory capacity (p<0.05) during exercise. Quadriceps strength was improved (p<0.05) and fatigue was attenuated as absolute and relative force after 3-minutes of electrical stimulation was significantly higher (p<0.05) following training. Conclusion: The present study shows that four weeks of individualized RT is sufficient to delay the onset of ventilatory constraint and attenuate peripheral muscle fatigue in patients with moderate to severe COPD. A similar training intervention may mitigate dyspnea clinically via the above mechanisms and could help patients ease into an aerobic based PR program.

Text

2018-10-09

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/67406

Health and Exercise Sciences

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/4.0/