We all know the multiple benefits that exercise and activity can have on our physical health however have you ever stopped to wonder if it can have any impact on our mental health? I first remember witnessing this experience as a teenager. It was a warm summer evening, the sun had just set, I was running shirtless in the country. The cool breeze against my skin, the air rhythmically moving in and out of my lungs, my mind felt crisp, calm with an overwhelming feeling of joy. Or more recently while training for a marathon. The goal for the day was to reach the 23-mile mark. Quiet darkness surrounded me as I hit the trail at 3 am. Several miles into the run, my body finally felt warmed up and seemed to be performing like a well-oiled machine. Romantic hits softly playing through my ear buds (I know, don’t laugh but that is my “go to” playlist for endurance runs) as the miles just seemed to tick away effortlessly. I enjoyed watching the horizon slowly lighten with the coming of the day. Finally crossing that 23-mile mark, the sense of accomplishment and pride was palpable. I went to work that day with the confidence that compared with what I had already completed, nothing couldn’t be overcome.

I am sure anyone reading this who has developed a habit of training can relate to similar experiences. So, what is it that causes these “feelings” we have all shared? We can turn to an article entitled “Exercise and Mental Health” from 2017 to better understand.

This article conducted a literature search over a 10 year period to compile anything that had to do with “exercise, physical activity, mental health, inflammatory disease, stress etc.” then compiled their findings into a review.  We will first discuss the mental health benefits of exercise with theorized reasons then delve into some the risks of exercise on our physical mental well-being.

Exercise and Mental Health

One overwhelming finding throughout their review was the evidence that regular physical activity can significantly improve mental health and lessen symptoms of depression, anxiety and stress (Mikkelsen et al, 2017) This impact has been shown to be as effective as psychotherapy.  The findings are across all age spectrums, from youth to elderly.

Both aerobic and anaerobic exercise have been shown to have beneficial effects. Two studies were conducted, one with 79 participants and one with 91 participants. In each study, the groups were assigned to a resistance or aerobic training program. At the end of 8 weeks, decreases in depression and anxiety scores were similar across both groups. (Mikelsen et al, 2017)

A meta-analysis review was conducted involving 42,264 participants. It looked at the beneficial impacts of exercise on those that suffered from generalized anxiety disorder vs those without a formal diagnosis. Among those with a formal diagnosis, the beneficial impacts on their anxiety scores and improved mental health symptoms were far greater, suggesting that those with a formal diagnosis of mental illness, can likely benefit even greater from regular training. Similarly, another meta-analysis review involving 48,207 participants looking at depression vs no-depression, again found similar findings. (Mikkelsen et al, 2017)

A study from 2004 looked at the psychological impacts of regular exercise on the elderly with dementia. It found that regular programmed exercise, increased fitness, cognitive function and positive behavior. (Heyn, 2004)

Mechanisms for Improvement

So, what is happening in the brain to cause such findings? The human body is an amazingly complex and intricate system that has been designed to move. To promote movement, systems have been built to induce feelings of pleasure with activity, thus encouraging ongoing activity. While we haven’t been able to say with certainty what is happening between our ears, we do have some theories that might help us better understand.

The endorphin hypothesis proposes that as we exercise, we release neurotransmitters into the brain tissue that help us better feel joy, loss of pain and a general sense of improved “well-being”. Several studies have been conducted, indeed, finding higher blood levels of endorphins after exercise. (Mikkelsen et at, 2017). A recent study conducted involving mice on a running wheel found significantly increased levels of natural endocannabinoids post exercise. These naturally occurring neurotransmitters stimulate the same receptors involved with eating chocolate or smoking marijuana.

The thermogenic hypothesis states that an increase in body temperature is responsible for an increase in mood elevation after exercise, thus decreasing the symptoms of anxiety. (Mikkelsen et al, 2017) However conflicting studies have been found that speak against these findings. Thus, while there may be some truth to this theory, the jury is still out as to the validity of this claim.

Another hypothesis involves the up regulation of mitochondria within the brain. Mitochondria are the “power houses” of the cell. It is within the mitochondria that energy conversion occurs. Like gasoline in a combustion engine, glucose enters the mitochondria, is oxidized, and produces cellular energy. This cellular energy is used to fuel processes that enable cellular growth and function.

 The brain is ever changing and adapting to its environment. While we used to think that neuro tissues were rather stagnant, we now understand the power of neuroplasticity. Neuroplasticity is the ability of the brain to change, grow, heal and adapt. It is thought that poor mental health may stem from poor neuroplasticity, or an inability to manage or deal with environmental stressors. (Mikkel et al, 2017) It is proposed that as we exercise, we signal the growth of mitochondria within the brain. These neuro mitochondria are then able to provide greater power output to facilitate improved neuroplasticity or “brain change”. This brain change improves our ability to handle stress and the demands of everyday life.

It is thought that exercise can increase serotonergic and adrenergic levels in the brain, effectively acting the same way as SSRI antidepressant medications. (Mikel et al, 2017). A study from 1999 out of the Archive on Internal Medicine evaluated 156 adults over the age of 50, battling depression. In this study, participants were divided into 3 treatment groups: anti-depressant group, aerobic exercise group or anti-depressant and exercise group. At 16 weeks, the researchers re-evaluated depression screening scores and found equal improvement among all participants. (Blumenthal et al, 1999)

There is much evidence that people suffering from depression and anxiety have a dysregulation of the HPA (Hypothalmic-Pituatary) axis. (Mikkel et al, 2017) The HPA axis is a system deep within the brain that helps with hormonal control. When we become stressed, we will naturally release increased levels of a hormone known as cortisol. This hormone will help prepare the body for higher physical demands. The problem however arises when we do nothing to act on these increased outputs of cortisol. If high levels of cortisol continue to be produced without any physical output, this can lead to a host of problems to include increased stress, anxiety and depression.

Not only do we see increased physiological benefits on our mental health from exercise, but much evidence also exists as to the psychological benefits of exercise. Focusing on training programs and routines can help distract us from negative thoughts and ongoing rumination. Reaching set goals, personal bests and overcoming our “hard” can all bolster self-esteem and confidence. The social aspect of working together with training partners can form relationships that help build belonging and community. Self-efficacy is the belief in one’s ability to succeed. Self-efficacy is gained by following set goals. Studies show that increased self-efficacy boosts self-esteem, reducing susceptibility to depression and anxiety. (Mikkel et al, 2017)

A study looking at the development of self-efficacy was conducted involving older women who suffered from heart failure. The researchers developed a home training program over a 12-week period that required the participants to implement a walking program. Those that adhered to the walking program reported improved quality of life and fewer depressive symptoms as opposed to those who underwent education alone. (Mikkel et al, 2017)

Newer research is now looking at the impact of inflammatory cytokines on mental health and general wellbeing. Cytokines are chemical messengers that tell cells to do stuff. In various diseases, inflammatory cytokines are released and may complicate the healing process or perpetuate the disease by impairing recovery.  Much like continuing to scratch a case of poison oak can slow the recovery, an outpouring of inflammatory cytokines slows our body’s ability to achieve an improved level of health, healing and wellness. We are now finding specific inflammatory cytokines that are reduced as we participate in physical activity. Like anyone recovering from a hip or knee surgery will attest, moving improves pain control and healing speed. This is the “down-regulation” of inflammatory cytokines at work.

Risks of Exercise

In the summer of 2021, I was training for my first “Iron Man” triathlon. Anyone involved in training for these vigorous events knows well that the training schedule is intense with many days of daily doubles and block runs. During this time, COVID was hitting our community quite hard. I was working at 2 hospitals and putting in many long stressful days. My typical day would usually start at 5 am with a 7–10-mile run, a long shift at the hospital and an evening bike ride of 25-30 miles.  My race was in Sept and my training was progressing well until the middle of August, at which time I started to notice something. My swim, run, and bike times began to slow down rather than improve.  I started to feel a tremendous mental drain. Training became harder and harder. The motivation was still there but the mental energy and focus required to achieve my training goals became harder and harder. Recover time took longer than expected.  In the first week of September (3 weeks before the scheduled race), I was doing hill sprints when I felt a twinge in my knee. I finished the run but woke up the next morning in so much pain that I couldn't walk.  I soon found I had just dived deep into a phenomenon known as “over-training”. Simply put, too much of a good thing is not a good thing. There is a limit to the beneficial effects of exercise. The risks of over-training involve chronic fatigue, depression, higher risks of infection and injury. Luckily, it takes a lot of very intense training without adequate recovery to reach that level, however it is a real phenomenon that we must watch for and recognize it’s coming.

Another risk we need to watch for is exercise dependence. A study involving 1601 college students that suffered from exercise dependence showed higher scores on anxiety / depression scales and increased negative effects involving mood and self-satisfaction. (Mikkel et al, 2017) Exercise dependence is the belief that our worth is centered around our ability to train. We erroneously believe that if we aren’t at the gym, we are fat and worthless. We often feel inadequate and push our bodies to extremes with exercise and diet.  Our exercise controls our life; we don’t use exercise to improve our life. This phenomenon is seen much more commonly in adolescence. It is a real condition that needs to be recognized before it becomes destructive.

From this review, we can clearly see that while some risks are in play with exercise, the overwhelming evidence points to the positive impact exercise can have on our mental health and well-being. Having a stressful day today, how about putting on a pair of running shows, blasting some Michael Bolton (or YOUR favorite long run tunes) and hitting the running trail this evening instead of the ice cream dish. I guarantee you will feel better with your decision for a healthier life.

Blumenthal, J.A., Babyak. M.A., Moore, K.A., Craighead, W.E., Khatri, P., Waugh, R., Napolitano, M.A., Forman, L.Lm, Appelbaum, M., Doraiswamy, P.M., Krishnan, K.R. (1999) Effects of Exercise Training on Older Patients with Major Depression. Archives of Internal Medicine, 159 (19), 2349-2356

Heyn, P., Abreu, B.C., Ottenbacher, K.J. The Effects of Exercise Training on Elderly Persons with Cognitive Impairment and Dementia: A Meta-analysis. Archives of Physical Medicine Rehab. 85 (10) (2004) 1694-1704

Mikkelsen, K., Stojanovska, L., Polenakovie, M., Bosevski, M. Exercise and Mental Health. Maturitas 106 (2017) 48-56

Author: Brett Williams FNP, CPT