Premature Fatigue in Veterans With Heart Failure: Neuronal Influences

A hallmark of patients with heart failure (HF) is premature fatigue which impairs their quality of life and depicts a major source of morbidity. Premature fatigue may be attributed to a) contraction-induced transient changes within muscles (i.e. peripheral fatigue) and/or b) failure of the central nervous system to 'drive' / activate locomotor muscles (i.e. central fatigue). Both determinants of fatigue can lead to a reduction in a muscle's force and power generating capacity and to a compromised ability to perform whole body activities (e.g. walking). Recent findings in health have documented that group III/IV afferent fibers from the working muscle play a critical role in the development of both components of fatigue. Specifically, group III/IV muscle afferents limit central motor drive (CMD) during exercise and thereby exaggerate the development of central fatigue. In contrast, muscle afferents optimize muscle O2 delivery through the precise regulation of circulation and ventilation during exercise and thereby attenuate the development of peripheral fatigue.