Impaired exercise capacity is a cardinal feature of chronic obstructive pulmonary disease (COPD) because it is associated with poorer quality of life [ 1 x [1] Kadikar, A., Maurer, J., and Kesten, S. The six-minute walk test: a guide to assessment for lung transplantation. J Heart Lung Transplant. 1997; 16: 313–319 PubMed | Google Scholar See all References , 2 x [2] Weisman, I.M. Cardiopulmonary exercise testing in the preoperative assessment for lung resection surgery. Semin Thorac Cardiovasc Surg. 2001; 13: 116–125 Abstract | Full Text PDF | PubMed | Scopus (27) | Google Scholar See all References ], increased use of healthcare resources [ 2 x [2] Weisman, I.M. Cardiopulmonary exercise testing in the preoperative assessment for lung resection surgery. Semin Thorac Cardiovasc Surg. 2001; 13: 116–125 Abstract | Full Text PDF | PubMed | Scopus (27) | Google Scholar See all References , 3 x [3] Casas, A., Troosters, T., Garcia-Aymerich, J. et al. Integrated care prevents hospitalisations for exacerbations in COPD patients. Eur Respir J. 2006; 28: 123–130 Crossref | PubMed | Scopus (290) | Google Scholar See all References , 4 x [4] Garcia-Aymerich, J., Hernandez, C., Alonso, A. et al. Effects of an integrated care intervention on risk factors of COPD readmission. Respir Med. 2007; 101: 1462–1469 Abstract | Full Text | Full Text PDF | PubMed | Scopus (90) | Google Scholar See all References ] and worse prognosis [ 5 x [5] Connors, A.F. Jr., Dawson, N.V., Thomas, C. et al. Outcomes following acute exacerbation of severe chronic obstructive lung disease. The SUPPORT investigators (Study to Understand Prognoses and Preferences for Outcomes and Risks of Treatments). Am J Respir Crit Care Med. 1996; 154: 959–967 Crossref | PubMed | Scopus (1055) | Google Scholar See all References , 6 x [6] Oga, T., Nishimura, K., Tsukino, M., Sato, S., and Hajiro, T. Analysis of the factors related to mortality in chronic obstructive pulmonary disease: role of exercise capacity and health status. Am J Respir Crit Care Med. 2003; 167: 544–549 Crossref | PubMed | Scopus (370) | Google Scholar See all References , 7 x [7] Pinto-Plata, V.M., Cote, C., Cabral, H., Taylor, J., and Celli, B.R. The 6-min walk distance: change over time and value as a predictor of survival in severe COPD. Eur Respir J. 2004; 23: 28–33 Crossref | PubMed | Scopus (367) | Google Scholar See all References ]. The six-minute walking test (6MWT) [ 8 x [8] ATS statement: guidelines for the six-minute walk test. Am J Respir Crit Care Med. 2002; 166: 111–117 Crossref | PubMed | Scopus (4688) | Google Scholar See all References ] [8] and the incremental cardiopulmonary exercise (CPET) [ 9 x [9] Roca J, Whipp BJ, editors. Clinical exercise testing. Eur Respir Mon. 6th ed.; 1997. Google Scholar See all References ] [9] are well accepted tests to evaluate exercise capacity in COPD (10–12). Yet, neither peak oxygen uptake (VO2 peak) determined during CPET [ 10 x [10] Foglio, K., Carone, M., Pagani, M., Bianchi, L., Jones, P.W., and Ambrosino, N. Physiological and symptom determinants of exercise performance in patients with chronic airway obstruction. Respir Med. 2000; 94: 256–263 Abstract | Full Text PDF | PubMed | Scopus (57) | Google Scholar See all References , 11 x [11] Oga, T., Nishimura, K., Tsukino, M., Hajiro, T., Ikeda, A., and Mishima, M. Relationship between different indices of exercise capacity and clinical measures in patients with chronic obstructive pulmonary disease. Heart Lung. 2002; 31: 374–381 Abstract | Full Text | Full Text PDF | PubMed | Scopus (33) | Google Scholar See all References , 12 x [12] Spruit, M.A., Watkins, M.L., Edwards, L.D. et al. Determinants of poor 6-min walking distance in patients with COPD: the ECLIPSE cohort. Respir Med. 2010; 104: 849–857 Abstract | Full Text | Full Text PDF | PubMed | Scopus (113) | Google Scholar See all References ] or the six-minute walking distance (6MWD) can be adequately predicted from the degree of airflow limitation [ 13 x [13] Nici, L. Mechanisms and measures of exercise intolerance in chronic obstructive pulmonary disease. Clin Chest Med. 2000; 21: 693–704 Abstract | Full Text | Full Text PDF | PubMed | Scopus (34) | Google Scholar See all References , 14 x [14] Pinto-Plata, V.M., Celli-Cruz, R.A., Vassaux, C. et al. Differences in cardiopulmonary exercise test results by American Thoracic Society/European Respiratory Society-Global Initiative for Chronic Obstructive Lung Disease stage categories and gender. Chest. 2007; 132: 1204–1211 Crossref | PubMed | Scopus (30) | Google Scholar See all References , 15 x [15] Rabe, K.F., Hurd, S., Anzueto, A. et al. Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease: GOLD executive summary. Am J Respir Crit Care Med. 2007; 176: 532–555 Crossref | PubMed | Scopus (3790) | Google Scholar See all References ] as an isolated factor, indicating that factors other than lung function impairment also modulate exercise capacity in COPD. Obesity [ 16 x [16] Franssen, F.M., O'Donnell, D.E., Goossens, G.H., Blaak, E.E., and Schols, A.M. Obesity and the lung: 5. Obesity and COPD. Thorax. 2008; 63: 1110–1117 Crossref | PubMed | Scopus (164) | Google Scholar See all References ] [16] is often associated with COPD and it has the potential to contribute to exercise limitation [ 17 x [17] Ora, J., Laveneziana, P., Ofir, D., Deesomchok, A., Webb, K.A., and O'Donnell, D.E. Combined effects of obesity and chronic obstructive pulmonary disease on dyspnea and exercise tolerance. Am J Respir Crit Care Med. 2009; 180: 964–971 Crossref | PubMed | Scopus (80) | Google Scholar See all References , 18 x [18] Sava, F., Laviolette, L., Bernard, S., Breton, M.J., Bourbeau, J., and Maltais, F. The impact of obesity on walking and cycling performance and response to pulmonary rehabilitation in COPD. BMC Pulm Med. 2010; 10: 55 Crossref | PubMed | Scopus (53) | Google Scholar See all References ], but its individual contribution to impaired aerobic capacity in these patients is unclear [ 18 x [18] Sava, F., Laviolette, L., Bernard, S., Breton, M.J., Bourbeau, J., and Maltais, F. The impact of obesity on walking and cycling performance and response to pulmonary rehabilitation in COPD. BMC Pulm Med. 2010; 10: 55 Crossref | PubMed | Scopus (53) | Google Scholar See all References , 19 x [19] Fabbri, L.M., Luppi, F., Beghe, B., and Rabe, K.F. Complex chronic comorbidities of COPD. Eur Respir J. 2008; 31: 204–212 Crossref | PubMed | Scopus (405) | Google Scholar See all References , 20 x [20] Garcia-Aymerich, J., Gomez, F.P., Benet, M. et al. Identification and prospective validation of clinically relevant chronic obstructive pulmonary disease (COPD) subtypes. Thorax. 2011; 66: 430–437 Crossref | PubMed | Scopus (173) | Google Scholar See all References , 21 x [21] Laviolette, L., Sava, F., O'Donnell, D.E. et al. Effect of obesity on constant workrate exercise in hyperinflated men with COPD. BMC Pulm Med. 2010; 10: 33 Crossref | PubMed | Scopus (23) | Google Scholar See all References ]. Different studies seem to indicate that obesity does not constitute a disadvantage during cycling exercise in COPD patients [ 18 x [18] Sava, F., Laviolette, L., Bernard, S., Breton, M.J., Bourbeau, J., and Maltais, F. The impact of obesity on walking and cycling performance and response to pulmonary rehabilitation in COPD. BMC Pulm Med. 2010; 10: 55 Crossref | PubMed | Scopus (53) | Google Scholar See all References , 21 x [21] Laviolette, L., Sava, F., O'Donnell, D.E. et al. Effect of obesity on constant workrate exercise in hyperinflated men with COPD. BMC Pulm Med. 2010; 10: 33 Crossref | PubMed | Scopus (23) | Google Scholar See all References ]. In contrast, Bautista et al. [ 22 x [22] Bautista, J., Ehsan, M., Normandin, E., Zuwallack, R., and Lahiri, B. Physiologic responses during the six minute walk test in obese and non-obese COPD patients. Respir Med. 2011; 105: 1189–1194 Abstract | Full Text | Full Text PDF | PubMed | Scopus (24) | Google Scholar See all References ] [22] reported that obese COPD patients had reduced 6MWD as compared with those with normal body weight. However, the mechanisms for the poorer walking performance in the obese COPD group were not fully established [ 23 x [23] Mahler, D.A., Gifford, A.H., Waterman, L.A., Ward, J., Machala, S., and Baird, J.C. Mechanism of greater oxygen desaturation during walking compared with cycling in patients with COPD. Chest. 2011; 140: 351–358 Crossref | PubMed | Scopus (23) | Google Scholar See all References ] [23] .