I just read this one and thought I'd share it.
Exercise Withdrawal Causes Mood Change Within Days
Fri May 12, 2006 11:13am ET
By Anne Harding
NEW YORK (Reuters Health) - People who exercise regularly start feeling
depressed and fatigued after just one week of forced inactivity, a new
Those who were in the best shape experienced the greatest loss in
fitness when they stopped exercising, and also showed the worst negative
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
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
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
At one and two weeks, Berlin and her team evaluated participants for
somatic (i.e., body-related) symptoms of depression such as fatigue, poor
appetite, difficulty sleeping and low energy, as well as mental
symptoms such as irritability, sadness and self-criticalness.
By one week, Berlin and her team found, the individuals who stopped
exercising reported more fatigue and other somatic symptoms than those who
had kept working out. At the second week, the non-exercisers reported
more mental symptoms as well.
While there was no statistically significant loss of fitness on average,
the researchers did find that the people who were the most fit -- as
measured by their VO2max, which represents the body's ability to use
oxygen efficiently -- showed the greatest loss in fitness. And those who
experienced the greatest drop in fitness showed the sharpest drop in
Berlin and her colleagues theorize 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.
Halting exercise, Berlin and her team propose, causes the balance to
shift back toward the sympathetic system. "If you're body's revved up all
the time, obviously you're going to start to feel tired," she added.
Berlin and her colleagues are now analyzing additional information from
the current study to explore their hypothesis.
SOURCE: Psychosomatic Medicine, March-April 2006.