Purpose: Little is known about the physiology of walking in chronic obstructive pulmonary disease (COPD). Our objective was to evaluate the cardiac and respiratory responses as well as the electrical activity of lower limb muscles during walking in patients with COPD compared with healthy controls.
Methods: Cardiorespiratory parameters were monitored during a 6-min walking test (6MWT) in 10 patients with COPD and 11 healthy controls. Surface EMG (sEMG) data were recorded in five muscle groups (soleus, medial gastrocnemius, tibialis anterior, vastus lateralis, and rectus femoris) of the right leg during walking. The integrated signal (iEMG) and the median frequency were obtained from the sEMG signal of each muscle group.
Results: Although the walking distance and speed were significantly reduced in patients with COPD compared with those in controls, patients walked at a higher percentage of peak V˙O2. The overall sEMG patterns were similar between patients with COPD and controls. A fall in the sEMG median frequency during the 6 MWT was observed for the vastus lateralis and the rectus femoris in patients with COPD and in controls suggesting a muscle fatiguing contracting profile.
Conclusion: The 6 MWT was performed at a relatively higher intensity in patients with COPD compared with healthy controls. The progressive fall in the sEMG median frequency of the vastus lateralis and rectus femoris in both groups suggested the occurrence of a muscle fatiguing profile during walking. The performance of a daily activity such as walking imposes a high physiological demand in patients with COPD.
1Centre de Recherche, Institut Universitaire de Cardiologie et de Pneumologìe, Université Laval, Québec, CANADA; 2Centre Interdisciplinaire de Recherche en Réadaptation et Intégration Sociale (CIRRIS) de l'Institut de Réadaptation en Déficience Physique de Québec, Québec, CANADA; and 3Leuven Catholic University, Leuven, BELGIUM
Address for correspondence: François Maltais, M.D., Centre de pneumologie, Hôpital Laval, 2725 Chemin Ste-Foy, Québec, Québec, Canada G1V 4G5; E-mail: firstname.lastname@example.org.
Submitted for publication August 2008.
Accepted for publication January 2009.