Patients with chronic heart failure (CHF) with preserved and reduced ejection fraction have lower peak oxygen uptake (VO2) values [ 1 Edelmann F. Gelbrich G. Duvinage A. et al. Differential interaction of clinical characteristics with key functional parameters in heart failure with preserved ejection fraction—results of the Aldo-DHF trial. Int. J. Cardiol. 2013; 169: 408-417 Abstract Full Text Full Text PDF PubMed Scopus (28) Google Scholar , 2 Izawa K.P. Watanabe S. Tochimoto S. et al. Relation between maximum phonation time and exercise capacity in chronic heart failure patients. Eur. J. Phys. Rehabil. Med. 2012; 48: 593-599 PubMed Google Scholar ]. Maximum phonation time (MPT), which is widely used to evaluate maximum vocal capabilities because it is quick, non-invasive, and inexpensive, correlates positively with peak VO2 in CHF patients in cross-sectional studies [ 2 Izawa K.P. Watanabe S. Tochimoto S. et al. Relation between maximum phonation time and exercise capacity in chronic heart failure patients. Eur. J. Phys. Rehabil. Med. 2012; 48: 593-599 PubMed Google Scholar , 3 Izawa K.P. Watanabe S. Oka K. et al. Differences in maximum phonation time based on body mass index in chronic heart failure patients. Int. J. Cardiol. 2014; 182C: 200-202 PubMed Google Scholar ]. To our knowledge, longitudinal changes in MPT and peak VO2 in CHF patients have not been studied. Therefore, the present study determined 1) longitudinal changes in MPT and peak VO2 and 2) the relation between delta MPT and delta peak VO2 in CHF patients.