Chasing the Blues Away

We are bombarded with information that partitions exercise and movement into isolated entities. We learn about heart rate zones, optimal step counts, and the strengths and limitations of maximal oxygen consumption (VO2max). We analyze power output and revolutions per minute, and critique stride length and leg turnover.  Yet, what ultimately brings so many of us back to the physical activities of our choosing is simply the fact that they make us feel good.

Indeed, the ability of exercise to lift spirits is quite profound and well established in the scientific literature.  There is now evidence that both aerobic and anaerobic exercise (namely moderate-intensity weight lifting) have the ability to significantly increase positive feelings, energy, and calmness, while reducing negative emotions and tiredness.  Yet, how is it that moving our bodies has any influence at all on our psychological state?

Numerous theories have surfaced over the years to account for the beneficial effects of exercise on mood.  Some have a psychological basis, while others stem from more biological roots. I’ve highlighted some of the mechanisms below that have received the most support from human and animal studies. These same theories also explain how exercise can reduce symptoms of chronic mood disorders, like depression.

Biological mechanisms

• Elevated Endorphins:  There is significant evidence to show that endorphins are secreted as a result of exercise.  The word endorphin comes from endogenous + morphine, which loosely translates to internally produced pain-killers.  While these chemicals do not act directly on the brain (cannot pass blood-brain barrier), they do have a calming effect in both humans and animals. In support of this mechanism, several studies have found that when endorphins are blocked, exercise does not have the same ability to relieve stress and anxiety.  Decreased endorphin levels may also explain why habitually active people often become irritable and restless when deprived of exercise.  ahem.
• Monoamine Hypothesis: Monoamines refer to a group of neurotransmitters that include norepinephrine (NE) and serotonin (5-HT).  Common anti-depressant drugs (Prozac, Zoloft, Paxil, etc.) function by regulating the release of these chemicals in our brains.  Substantial research suggests that physical activity modifies the release of NE and 5-HT in much the same way, making  these neurotransmitters more readily available in synapses.
• BDNF Hypothesis: This theory primarily speaks to the long-term effects of exercise and may be especially significant in explaining how exercise can help depression. Brain-derived neurotrophic factor (BDNF) promotes neural growth and generally works to keep neurons healthy.  Some have described it as “miracle grow” for the brain, and it is key to many of the topics I blog about.  It is relevant here because BDNF also has antidepressant effects.  Both antidepressant drugs and exercise increase levels of BDNF in the hippocampus.  This region is classically associated with learning and memory, but has also been found to play a role in depression.  More on these important relationships later!
• Other biological theories include the reduction of cortisol (a stress hormone) and better regulation of the hypothalamic-pituitary-adrenal (HPA) axis.  These have strong implications for mood, but more directly impact stress and anxiety.

Psychological mechanisms

• Sense of Mastery and Self-efficacy:  Because exercise is often viewed as a challenging activity, the ability to commit to it on a regular basis often results in a sense of control, accomplishment, and satisfaction.  Merely setting fitness goals can also fuel a sense of purpose.  These can all contribute to both immediate and long-term boosts in mood.
• Distraction:  Exercise can serve as a diversion from negative thoughts and other unfavorable stimuli (overflowing inboxes, screaming children…).  By forgetting our worries and focusing on our physical movements, we can temporarily alleviate stress and break cycles of unconstructive thinking.
• Exposure to Nature:  Physical exercise often gives people a reason to get outside, and as discussed in my last entry – doing so can positively impact mood states.
• Social Factors:  Interacting with others is important for our overall mental well-being. While some prefer the solitude of exercising alone, exercising with others can foster a reciprocal sense of support.  You may help another reach their fitness and performance goals, and someone else may do the same for you. An additional benefit of exercising with people is that you are less inclined to skip a workout if another is depending on you to be there.  Unsurprisingly, this increased adherence to exercise equates to more of it!

Most likely, the benefits of exercise on mood result from a combination of many of these theories, as well as underlying genetic factors.  Regardless of how exactly it is that exercise makes us feel good, I suspect most of us are just glad that it does!  There may be hope for Eeyore yet.

Comments and questions always welcome!

Key References:

• Blake, H. (2012). Physical activity and exercise in the treatment of depression.  Frontiers in Psychiatry, 106(3), 1-4.
• Landers, D., & Arent, S. (2007). Physical activity and mental health. In G. Tenenbaum,& R.C. Eklund (Eds.). Handbook of sport psychology (3rd ed.) (pp. 469- 491). New York: J. Wiley & Sons.
• Peluso, M., & Guerra de Andrade, L. (2005). Physical activity and mental health: the association between exercise and mood. Clinics, 60(1), 61-70.