Breathing disorders, including sleep apnea, are common among congestive heart failure patients [ 1 Javaheri S. Parker T.J. Liming J.D. et al. Sleep apnea in 81 ambulatory male patients with stable heart failure. Types and their prevalences, consequences, and presentations. Circulation. 1998; 97: 2154-2159 Crossref PubMed Scopus (1030) Google Scholar , 2 Tremel F. Pepin J.L. Veale D. et al. High prevalence and persistence of sleep apnea in patients referred for acute left ventricular failure and medically treated over 2 months. Eur. Heart J. 1999; 20: 1201-1209 Crossref PubMed Scopus (129) Google Scholar , 3 Sin D.D. Fitzgerald F. Parker J.D. Newton G. Floras J.S. Bradley T.D. Risk factors for central and obstructive sleep apnea in 450 men and women with congestive heart failure. Am. J. Respir. Crit. Care Med. 1999; 160: 1101-1106 Crossref PubMed Scopus (951) Google Scholar ], with the mechanisms explaining this relationship discussed elsewhere [ 4 Sharma B. McSharry D. Malhotra A. Sleep disordered breathing in patients with heart failure: pathophysiology and management. Curr. Treat. Options Cardiovasc. Med. 2011; 13: 506-516 Crossref PubMed Scopus (13) Google Scholar , 5 Sharma B. Owens R. Malhotra A. Sleep in congestive heart failure. Med. Clin. N. Am. 2010; 94: 447-464 Abstract Full Text Full Text PDF PubMed Scopus (62) Google Scholar ]. There is considerable evidence to support an association between physical activity and sleep apnea [ [6] Araghi M.H. Chen Y.F. Jagielski A. et al. Effectiveness of lifestyle interventions on obstructive sleep apnea (OSA): systematic review and meta-analysis. Sleep. 2013; 36 (1562 A-1562E): 1553-1562 Crossref PubMed Scopus (129) Google Scholar ] and sleep-related parameters [ 7 Loprinzi P.D. Cardinal B.J. Association between objectively-measured physical activity and sleep, NHANES 2005–2006. Ment. Health Phys. Act. 2011; 4: 65-69 Crossref Scopus (103) Google Scholar , 8 Loprinzi P.D. Loprinzi K.L. Cardinal B.J. The relationship between physical activity and sleep among pregnant women. Ment. Health Phys. Act. 2012; 5: 22-27 Crossref Scopus (17) Google Scholar , 9 Loprinzi P.D. Finn K.E. Harrington S.A. Lee H. Beets M.W. Cardinal B.J. Association between physical activity behavior and sleep-related parameters of adolescents. J. Behav. Health. 2012; 1: 286-293 Google Scholar ], but the association between free-living physical activity and sleep apnea among congestive heart failure patients has been considerably less investigated [ 10 Izawa K.P. Watanabe S. Oka K. et al. Relation between sleep quality and physical activity in chronic heart failure patients. Recent Pat. Cardiovasc. Drug Discov. 2011; 6: 161-167 Crossref PubMed Scopus (6) Google Scholar , 11 Ueno L.M. Drager L.F. Rodrigues A.C. et al. Effects of exercise training in patients with chronic heart failure and sleep apnea. Sleep. 2009; 32: 637-647 PubMed Google Scholar , 12 Paparrigopoulos T. Tzavara C. Theleritis C. Soldatos C. Tountas Y. Physical activity may promote sleep in cardiac patients suffering from insomnia. Int. J. Cardiol. 2010; 143: 209-211 Abstract Full Text Full Text PDF PubMed Scopus (15) Google Scholar ]. To expand our knowledge on this topic, the purpose of this study was to examine the association between physical activity and sleep apnea among congestive heart failure patients.