Contributor: Steven Stroud

Exercise intolerance is a hallmark of HF. We tend to blame the weak heart for not delivering enough oxygen to exercising muscles, but this is wrong.

Muscles without oxygen are hypoxic. This could happen because of poor cardiac output or because the skeletal muscle cells are not handling oxygen well. In other words, does low cardiac output cause fatigability or are there differences in skeletal muscle energetics in HF?