. . . Published ahead of Print Medicine & Science in Sports & Exercise ® Published ahead of Print contains articles in unedited manuscript form that have been peer reviewed and accepted for publication. This manuscript will undergo copyediting, page composition, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered that could affect the content. Copyright © 2017 American College of Sports Medicine Challenges with Percent Predicted Maximum VO 2 in Patients with Heart Failure Clinton A. Brawner 1 , Jonathan K. Ehrman 1 , Ali Shafiq 2 , Matthew A. Saval 1 , Stuart D. Russell 3 , David E. Lanfear 1 , and Steven J. Keteyian 1 1 Division of Cardiovascular Medicine, Henry Ford Hospital, Detroit, MI 2 Division of Cardiology, Aurora Health Care, Milwaukee, WI 3 Division of Cardiology, Johns Hopkins Hospital, Baltimore, MD Accepted for Publication: 18 September 2017 ACCEPTED