Physiological benefits of exercise

The many benefits of physical activity (exercise) for our physical and mental health have been widely researched and promoted.

Although most people know what the benefits are, knowledge of the physiological basis behind these effects on our body and mind are not as common.

Today I will briefly introduce how exercise can help uplift low mood and calm an anxious mind.

The effects of exercise on depressed individuals have been studied for decades and several helpful psychological and physiological mechanisms have been found. There are three main physiological hypotheses. Firstly, the Monoamine Hypothesis states that exercise reduces the levels or cortisol and adrenaline (stress hormones) and increases the availability of brain neurotransmitters - such as serotonin and dopamine, which plays a big role in our brain’s reward and pleasure system.

Secondly, the Endorphin Hypothesis states that exercise increases the release of endorphins which are body’s natural painkillers and mood elevators. Thirdly, the Thermogenic Hypothesis states that the increase in our body temperature from exercise relaxes our brain and muscles.

This is why cardiovascular, high intensity, or resistance training are beneficial for lifting our mood.

On the other hand, when we are anxious, we want to slow our heart rate and breathing down to go to a state of calm.

Our body’s involuntary functions – such as digestion, heart rate, and hormone production and release – are controlled by Autonomic Nervous System (ANS). The ANS has two main parts:

The parasympathetic nervous system (PNS), which controls homeostasis and the body at rest, is responsible for the body's "rest and digest" function. The sympathetic nervous system (SNS), which controls the body's responses to a perceived threat, is responsible for the "fight or flight" response.

The SNS and PNS counteract each other – when one is active, the other is less active. When we are feeling stressed or anxious, our SNS is active and increases our heart rate, muscle tension, and the release of adrenaline. This is when we want our PNS to become more active. We can do this by engaging in diaphragmatic breathing (also known as belly breathing). Diaphragmatic breathing encourages full oxygen intake and stimulates the PNS via Vagus nerve. The Vagus nerve is 80% afferent, meaning it mostly feeds the signals from our internal organs to the brain. By creating a calm body, we can create a calm mind.

Resources and references

• https://www.health.harvard.edu/mind-and-mood/relaxation-techniques-breath-control-helps-quell-errant-stress-response
• https://www.breathingtree.co.uk/science-breath/
• https://www.diffen.com/difference/Parasympathetic_nervous_system_vs_Sympathetic_nervous_system
• https://www.npr.org/2010/12/06/131734718/just-breathe-body-has-a-built-in-stress-reliever?t=1605203704754
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5709795/
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5050399/
• https://www.scielo.br/scielo.php?pid=S1807-59322005000100012&script=sci_arttext
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5859128/#:~:text=The%20vagus%20nerve%20represents%20the,%2C%20digestion%2C%20and%20heart%20rate
• https://www.health.harvard.edu/staying-healthy/exercising-to-relax
• https://www.medicalnewstoday.com/articles/326090