People who exercise regularly start feeling depressed and fatigued after just one week of forced inactivity, a new study shows.
Those who were in the best shape experienced the greatest loss in fitness when they stopped exercising, and also showed the worst negative mood symptoms.
Ali A. Berlin of the Uniformed Services University of the Health Sciences in Bethesda, Maryland says she's not sure that the results would apply to a person who was skipping workouts of their own accord, perhaps to do something fun. "I think future research is needed to really answer that question."
Sedentary people are more likely to be depressed, while a number of studies have suggested that symptoms of depression like fatigue, tension and irritability can develop in a fit person who stops exercising, Berlin and her colleagues note in the March-April issue of Psychosomatic Medicine.
To get a clear picture of how exercise withdrawal might affect mood, the team looked at 40 men and women who normally exercised at least three times weekly for at least 30 minutes. Half were instructed to stop exercising for two weeks, while the other half continued with their regular routine.
Berlin and her colleagues theorise that exercise helps preserve mood by shifting the body's nervous system balance away from the sympathetic nervous system, which is responsible for triggering the "fight or flight response," toward the parasympathetic nervous system, which quiets the body. "Exercise can affect this balance, it basically lets you calm down more efficiently," she explained.