Inactivity - What Causes Fatigue: Chronic Fatigue

Content provided by the Faculty of the Harvard Medical School

Inactivity

In addition to its contribution to sleep problems (see "Sleep difficulties"), inactivity can also cause fatigue by inducing changes in the muscles and cardiovascular system, as well as in one's psychological state. For one thing, muscles lose bulk with inactivity, and the smaller they are, the less powerful they are. People who have a limb immobilized because of injury or illness begin losing muscle cells within just six hours, leaving the muscle weaker and more easily fatigued. With weaker muscles, you'll expend more effort to accomplish even simple things like climbing stairs.

Lack of exercise also causes cardiovascular changes that affect your energy level during periods of physical exertion. Compared with an active person, a sedentary person has, among other signs of fatigue during exercise, a higher heart rate and lower oxygen consumption. Inactivity also has psychological effects. The less active you are, the less active you want to be. People who don't exercise have a greater perception of fatigue than people who do.

Last updated:	January 23, 2007