The present invention provides for methods of treating and slowing the onset of heart failure. The inventors have determined that myosin binding to unphosphorylated Myosin Binding Protein C (MyBP-C) plays a key role in the diminution of cardiac contractile force and frequency in heart failure. The present invention provides peptide inhibitors of the MyBP-C/myosin interaction, thereby increasing both cardiac contractile force and frequency in the failing heart, as well as in patients not yet exhibiting frank heart failure.
