Releasing Anxiety Through Exercise

Many of you may have attended the biology seminar this evening titled, “Acute Exercise for the Treatment of Anxiety”, which was presented by Aggie Mika from the University of Colorado, Boulder.  It proposed the idea of using acute exercise as a way to prevent, or improve the symptoms of anxiety, which is the most common mental illness in the United States.  There are many subsections of different anxiety disorders like obsessive compulsive disorder, general anxiety, PTSD and other panic and anxiety based mental ailments.  The study discussed in this presentation was focused on using fear conditioning, followed by extinction of the fear stress response, and finally testing the results found in the fear renewal stage of this overall process. 

Just to give a quick a background for those who did not attend the talk; the experimental procedure included introducing a stimulus (a tone) to rats and then pairing it with a foot shock.  After this fear conditioning took place, the rats were then put through a process of extinction to rid of the previously conditioned fear from the tone associated with the shock.  However, one group was housed in a unit that allowed for mobility and exercise from a running wheel during the extinction process, and the other group was housed in a locked wheel that did not allow for exercise.  Afterwards, the rats were placed in a new environment to test the fear renewal phase, their fear response behaviors were observed, as well as the neural mechanisms and their physiological responses were also examined through blood and brain tissue analysis after immediate sacrifice of the rodents.

It was found that not only did the rats who were allowed exercise during the extinction phase have a  reduced fear renewal in recorded fear specific behaviors (i.e. freezing), but in collected blood samples they also showed decreased levels of corticosterone, a stress hormone produced in the cortex of the adrenal gland in rodents as a stress response.  The question became; what was the specific mechanism producing these results? This then gave rise to the hypothesis that it was the reward pathways being stimulated, that in return inhibited the prelimbic region of the medial prefrontal cortex that signals the amygdala in the activation of a fear expression.  With a decreased activation to this region of the brain there will be a decreased stress response, and therefore, lower levels of stress hormones released in the body.  It was thought that instead of just diminishing a negative event being associated with the sound of the tone, that there was now a positive, rewarding event of exercise being newly coupled with the sound of the tone that was activating this reward pathway in the brain.  Overall, the theory is that this reward pathway will then trump the fear response in the renewal session.  By using markers on the brain tissue collected from the rodents, they were able to track the presence of C-fos mRNA in Dynorphin cells which are associated with the activation of neurons in the reward circuitry.  This activation in the reward pathway as a product of the acute exercise variable ultimately inhibited the effects in the mPFC, which is the regulator of the fear response to the amygdala which would normally have resulted in otherwise noted fear expressions.

So what does this mean for humans?  I believe that exercise, as a form of a stress reducing agent or reward pathway activator, is maybe more of an outlet for that built up stress response that also happens to have these subsequent effects as mentioned.  In Robert M. Sapolsky’s book, “Why Zebras Don’t Get Ulcers” he mentions the importance of stress outlets for our frustration, or in this case fear.  A main component of the outlet is that it is a distractor for the initial stressor, which can dampen the response to it.  Also, if we look at what the stress response is ultimately designed for; fight or flight, we may begin to have a better understanding of why exercise is an optimum physical and psychological outlet as opposed to just eating something loaded with sugar, or receiving some other stimulus that activates the same reward pathway.  The stress response’s goal is to prepare the body for this event in which high amounts of energy are assumed to be needed, like to run away or fight for your life.  If we at least allow our body to expel some of this built up energy through forms of exercise, then maybe we can allow it get back to its desired homeostatic balance more quickly if it believes that the stressor is gone once the exercise is over.  This is what I believe sets exercise apart from other forms of stress reducing therapy such as pharmaceutical or other alternative medical solutions.  Exercise is at least accommodating for the natural physiological response to the stressor which is to fight or flight in some way or another.  

In terms of a psychological relation to this stress reduction, which was ultimately the goal in this study; to work towards improvements in anxiety disorder symptoms, a decreased physiological response makes for a decreased psychological response and ultimately vice-versa in a continuing negative feedback loop.  Exercise allows for not only a physical release, but a mental one as well.  Like mentioned before, this stress outlet of working out serves as a mental distractor from the original stressor.  As opposed to lying in bed awake with nothing else to do but have your mind run rampart over all of the tasks you have yet to do for the week, or upcoming tests, or worry about relationships in your life, exercise gives your mind another focus that can hopefully dull the intensity of that psychological stressor, and maybe even eliminate it once a greater rationale sinks in that maybe it’s not as life threatening as you thought getting a C on an exam was.      

References:

Mika, Aggie. ""Acute Exercise for the Treatment of Anxiety." Department of Biology Seminar Series. Regis University, Denver. 04 Nov. 2013. Lecture.

Sapolsky, Robert M. Why Zebras Don't Get Ulcers: A Guide to Stress, Stress Related Diseases, and Coping. New York: W.H. Freeman, 1994. Print.