How Exercise Could Be Making You Unhealthy

If you dread your workouts, you may not be getting all of the benefits for which you're torturing yourself. A number of studies point toward an inverse relationship between exercise benefits and the psychological stress associated with being forced to exercise.

The studies, using rats, make a distinction between voluntary exercise and forced exercise. In voluntary exercise groups, the rats engage in "free wheel running." They have running wheels in their cages, and they can get on and off at will and run at whatever speeds suit them. They exercise when and how they want to. The forced exercise groups engage in "forced treadmill running." This training requires the rats to run when, how long and how fast the experimenters choose. They often have to be prodded using negative stimuli.

The result? As you might expect, both groups burned calories and improved fitness levels. However, differences appear in psychological behavior outcomes and in neurological, endocrine and immune system function.

For example, the forced rats displayed more anxiety and were less likely to explore new environments. In contrast, voluntary free wheel running reduced behavioral depression and learned helplessness that often accompanies exposure to stress. Learned helplessness behaviors in rats resemble the behaviors of people suffering from anxiety and depression. They respond to situations with exaggerated fear and fail to escape stresses from which they could normally remove themselves. Voluntary exercise minimizes or even prevents these depression behaviors.

Voluntary exercise is also more effective than forced exercise in promoting healthy neurons (nerve cells) in the brain and in enhancing the recovery of movement after a stroke. A 2011 animal study examined the effects of voluntary versus forced exercise on Brain-Derived Neurotrophic Factor (BDNF) and motor recovery. BDNF is a growth factor involved in preserving and forming nerve cells and is critical for learning and memory. In this animal study, rats who had suffered strokes underwent rehabilitation that involved physical exercise. The rats in the voluntary exercise group improved their movement deficits significantly more than those in the forced exercise group. They also had significantly higher levels of BDNF than the forced exercise group.

Yet another animal study looked at the effects of voluntary exercise on the ability to deal with acute stress. Rats engaged in either voluntary running or no running for a period of four weeks. Those in the voluntary running group showed less behavioral depression and no suppression of the immune system in response to acute stress. Those in the sedentary group took longer to recover from behavior depression and had immune system impairment.