We all know that exercise is hugely important for our physical well-being, with obvious benefits including weight management, increased overall strength and a better ability to cope with the demands of daily life (for example, having the strength to carry all your shopping bags at once, or the fitness level required to sprint for your bus when you’re running late).
However, in this blog we’re going beyond the physical benefits of exercise to explore the effect that it can have on our mental health. We’re all familiar with the phrases “runner’s high” and “endorphin rush”, so we know in a vague sense that there is definitely a link between moving our bodies and boosting our moods, but what exactly causes this and how can we harness it, to become our healthiest and happiest selves – in both body AND mind?
The stress response
Firstly, let’s have a quick GCSE Biology recap and remind ourselves what we mean when we talk about the body’s stress response. Also known as the “fight or flight response”, it can be thought of as our body’s emergency response. Triggering it is the main function of our body’s sympathetic nervous system, a component of our autonomic (i.e. involuntary) nervous system.
The stress response is activated when we find ourselves in a stressful or life-threatening situation. Substances including adrenaline and cortisol are released, causing our heart rate to spike and our breathing rate to increase. Our muscles are primed to spring into action. It’s essentially Mother Nature’s way of shouting at us to keep away from danger.
For our ancestors, this stress response mechanism worked perfectly well – early humans did not have to deal with minor day-to-day stressors, so the fight or flight response was only triggered when it was really needed, in dangerous and life-threatening situations (like being chased by a bear while foraging for food). However, there now exists a huge disconnect between our stress response and modern life.
We deal with far fewer life-threatening situations that should trigger the fight or flight response. However, we also face many more minor challenges, like difficult work meetings, annoying traffic jams or hectic exam schedules. Our bodies react to these with the same highly-geared stress response evolved by early man, meaning that we end up responding to all manner of daily interactions and situations as though they’re life-threatening.
Flipping the stress switch “on” too often can put immense pressure on both mind and body. It can cause anxiety, depression, adrenal fatigue and compromised immunity. While there are a number of things we can do to address this, research is increasingly pointing to exercise as being an important tool in our arsenal to deal better with stress – and to support our wider mental health as a whole. The neuroscience of physical fitness is an exciting and rapidly-developing research topic that is already changing the way that we approach stress and mood disorders.
The impact of exercise on our brain
Studies show that physically-trained individuals show lower physiological and psychological responses to psychosocial stress. Very simply put, people who exercise more are able to cope with stress in a more effective way.
How? Studies have shown that “enhanced physical exercise facilitates neuroplasticity of certain brain structures and as a result cognitive functions as well as affective and behavioural responses”. Research suggests that exercise helps to promote neural growth, decrease inflammation and establish new activity patterns in the brain.
Exercise, and the increased blood flow that it causes, represents an important physiological stimulus on our hypothalamic pituitary adrenal (HPA) axis, our central stress response system made up of the hypothalamus, pituitary gland and adrenal glands. The brain areas most changed by exercise are:
- The hippocampus – the seahorse-shaped structure that sits across both sides of the brain and is responsible for long-term memory
- The amygdala – the small pea-shaped part of our brain that deals with emotional memory. Any impairment of this part of the brain is associated with heightened feelings of anxiety and fear
- The frontal cortex – this is the front-most part of our brain, closely linked to personality traits and our ability to think and make rational decisions
The hippocampus and the amygdala are both part of the limbic system, a set of brain structures which support a variety of functions including emotional processing, behaviour, motivation and memory formation. The impact of exercise on the amygdala, which controls our fear response to stress and regulates our emotion, is of particular interest. Disorders of the amygdala are closely linked to heightened feelings of anxiety and distress. Studies show that aerobic exercise counteracts dysfunctional activations of the amygdala, suggesting that simply being active helps to reduce the impact of stressors on mood.
Impact of exercise on neurotransmitters
A neurotransmitter is a chemical “messenger” that carries signals between brain cells and other cells in the body. These signals affect a huge number of both physical and psychological functions, including heart rate, sleep, appetite, mood and emotions.
The neurotransmitters most impacted by exercise are:
- Dopamine – the “pleasure” chemical, linked to learning and feelings of euphoria
- Serotonin – the “content” chemical, linked to memory and feelings of well-being
- Glutamate – a key driver of learning, memory and brain plasticity
- GABA – plays a key role in emotional processing
Exercise and endorphins
“That was SUCH a rush!”… Skydiving, spicy peppers, sex, chocolate, laughter… What do these things have in common? They are all triggers for the release of endorphins. Natural mood-lifters, endorphins are chemicals naturally produced by our nervous system to help our bodies cope with pain or stress. They have a similar impact to opioids, causing a “rush” of euphoria or intense happiness.
Exercise not only promotes the release of endorphins, it also increases our level of serotonin which, together with dopamine and endorphins, is often described as one of our body’s “happy hormones”. Serotonin helps our brains to regulate mood, sleep and appetite.
In the short term, exercise can therefore be used to lift mood and shift our focus away from the stressors we’re currently experiencing. However, there are long-term benefits of these short-term endorphin rushes, too. When your brain is flooded with these so-called “happy hormones”, it undergoes significant molecular and structural alterations. What may seem like temporary mood boosts actually change brain chemistry in permanent ways, enhancing mood, attention and memory.
Traditionally thought of as psychological ailments, depression, anxiety and stress are now recognised as neurological diseases, with visible changes in brain structure clear in sufferers.
Depression is thought to be related to errors in our brain’s production of dopamine and serotonin, with reduced amounts being linked to symptoms such as an inability to feel pleasure from activities that would usually bring joy. Studies have shown that exercise can treat mild to moderate depression as effectively as commonly-prescribed antidepressants – without the associated side effects.
In a study by Craft and Perna (2004), individuals with major depressive disorder were able to significantly reduce their symptoms after 16 weeks of an aerobic exercise programme. Similarly, the Harvard T.H. Chan School of Public Health found that running for 15 minutes a day or walking for 60 minutes reduced the risk of major depression by 26% (and that prescribing exercise to sufferers of depression greatly reduced the risk of relapse).
When it comes to preventing the onset of depression in the first place, studies have shown that those who regularly exercise are less depressed or anxious than those who do not, further reinforcing the case for physical exercise to be a first port of call when treating mood disorders.
Anxiety, trauma and PTSD
Meanwhile, anxiety disorders have shown to be linked with errors in glutamate and GABA, the two neurotransmitters that have the greatest impact on mood and the overall health of our nervous system. Reduced GABA in the synapses is linked to heightened anxiety and low mood.
There is also evidence that exercise can help the body to move away from the immobilisation stress response that is often a symptom of PTSD or trauma. While the science behind this is not yet fully understood, intuitively it makes sense – focusing on the physical sensations of your joints and muscles as you exercise can help to move your focus elsewhere and become “unstuck”.
Other benefits of exercise on our mental health include:
- Promoting a good sleep pattern (sleep is key for overall brain health and has proven to be a key driver in reducing stress and making weight loss easier)
- Focusing on a skill enables you to feel a sense of accomplishment and is linked to higher feelings of self-worth, confidence and self-efficacy
- Studies have shown that exercise promotes growth in the hippocampus, which is responsible for emotion, memory and the autonomic nervous system
When embarking on a fitness journey, it’s all too easy to focus on the aesthetic benefits or the weight loss target that you have set yourself. And while these are definitely good goals to have, we’d also encourage you to appreciate the incredible effect that it can have on your mental health, too. Something we hear a lot from our clients is, “I was stressed when I came in, but I feel so much better now”. That is as important to us as any strength gains or weight loss!
Sources / Interesting links