Determinants and Correlates of Exercise Capacity in Heart Failure.

T he heart, lungs, blood, vasculature, and skeletal muscle integrate in a complex way to allow humans to interact with their environment, through locomotion and other forms of physical exercise (1). This interaction becomes challenged in people with the clinical syndrome of heart failure (HF) (2). In addition to the very reasonable desire to live longer, people with HF also want to be able to do things, like ascending stairs, carrying groceries, or mowing the lawn. As health care providers, it is imperative for us to understand why they are limited, so that we can offer ideas for effective ways to improve exercise capacity and thus quality of life.