Physical Activity, Stress & Mental Health
- Rise of mental health issues.
- Benefits of physical activity on mental health.
- Mechanisms through which physical activity improves mental health.
- The stress responsive systems
- Physical activity acts as a buffer against stress
- Physical activity promotes an anti- inflammatory state
- Physical activity enhances neuroplasticity and growth factor expression
The HPA axis contains the three endocrine glands, the hypothalamus, the pituitary gland and the adrenal gland, and is our primary stress response system. The hypothalamus will perceive the threat, whether physically or psychologically. It will release corticotropin-releasing hormone (CRH). CRH will bind to receptors on the pituitary gland and stimulate the release of adrenocorticotropic hormone. This will stimulate the release of cortisol from the adrenal gland. The bodies constant want to remain in balance controls all of it's systems. Like any other system, it responds to stress. Many understand this as the 'fight or flight' response to stress:
- The body perceives a threat. The concentration of cortisol will rise.
- Glucocorticoids and catecholamines are released in an effort to mobilise energy for the body to fuel it's response, along with a rise in heart rate and alertness.
- They also work together to produce a stress response in the immune system. This immune response is responsible for terminating the stress and returning the system to normal levels.
- Continued exposure to glucocorticoids will exert a suppressing affect to restore the immune system back to baseline levels.
It is this regular activation of the stress response system and immune system which maintains it's efficiency. During periods of prolonged/chronic stress (particularly exam period), these systems become maladaptive and cease to work optimally, leading to dysfunction of our immune systems. Most often it is presented as chronically elevated cortisol levels or sustained activation of glucocorticoids (far beyond normal levels). Dysregulation of the HPA axis are mentioned in many stress related disorders. Regular activation of these systems can keep them functioning optimally and greatly reduce the risk of succumbing to a stress related illness and promote a more resilient biological profile. Physical activity does not have to be planned or strenuous. Regular bouts of unplanned spontaneous activity are just as effective keeping the HPA axis functioning optimally.
As mentioned above, exercise can be used as a stressor. The body reacts to these stressors systematically to try and defend itself and then return itself to a state of equilibrium. With a better understanding of the process, it should now be clearer that people with greater physical fitness are better able to deal with normal stressors in life as their body has already adapted to dealing with them from the involvement in regular physical activity. In this way we can see that regular activity and over physical fitness can act as a buffer against external stressors and allow you to deal with them more effectively.
Those with higher fitness levels exhibit lower cortisol levels and anxiety in response to stress. The research has shown that through regular exposure to physical activity, you can 'stress train'. Repeated exposure to the same stressor will eventually lead to a physiological adaptation allowing your to expose yourself to stress and react/recover quicker compared to untrained individuals, allowing you to cope better in stressful situations. Following on from this train of thought we may be able to increase an individuals emotional stability, reduce irritability to stress/change and reduce anxiety during stressful situations.
The human body contains many inflammatory cytokines (cells secreted by the immune system). Some pro-inflammatory and some anti-inflammatory. Pro inflammatory cytokines have the ability to influence every pathophysiological domain relevant to depressive symptomatology (Miller, Maletic and Raison, 2009).
Those with higher fitness levels also tend to have a reduction in baseline levels of pro-inflammatory markers. Higher levels of visceral fat also show a higher level of circulating pro-inflammatory markers. Thus lending to the notion that regular physical activity leads to a reduction in visceral fat, leading to a reduction in pro-inflammatory markers. During exercise, contracting skeletal muscle releases cytokines which have anti-inflammatory properties. These cytokines also increase insulin sensitivity (positive) and improve the characteristics symptomatic of depression and other conditions. All of this contributes to improved mood, cognition, metabolic function and overall well-being.
Neurotropic factors (NTFs) are molecules which aid in the development and maintenance of neurons, the basic working unit of the brain. Chronic stress decreases the expression of NTFs thus reducing neurogenesis (development of nervous tissue). Regular physical activity can help reverse these effects by increasing neurogenesis through increasing the release and concentration of certain growth factors (Rothman et al., 2012). These growth factors, such as insulin like growth factor (IGF-1) and brain derived neurotropic factor (BDNF) expressed to a greater degree in physically fit individuals. They help in increasing neuroplasticity, the ability of the brain to reorganise itself in response to it's environment or tasks. May come in handy when studying for exams when you need to take in a lot of information!
These areas of research are still in it's infancy and anything beyond that which is discussed above would be nothing more than speculation.
This article was written in response to several discussions we have had with people mainly around exam period, but also those involved in high pressure work environments. The first thing that usually gets drops is physical activity and more work/study is assigned in it's place. While it's not always possible, hopefully the above information gives you enough food for thought to not replace physical activity completely. Practical advice on this part would be to record your notes on your mobile device or find an educational resource/podcast and listen to it while engaging in some form of activity be it a simple 30-40 minute walk.
The importance of physical activity on all aspects of our lives cannot be understated. With mental health issues prevalent throughout our society it is imperative that we attempt to curb the rise by doing whatever we can. Increasing physical activity (in all ages) is one of the easiest things we can do. It doesn't require a huge amount of time and best of all it doesn't cost any money to go outside for a walk/jog/run.
Take Home Message
- Cope better in stressful situations.
- Are more emotionally stable during stressful periods.
- React better during sudden stressful events.
- Are more likely to have an internal anti-inflammatory environment in which promotes good mood and positive well-being.
- Brains work more efficiently. Providing a better environment in which the brain can adapt to it's current situation.
Acute bouts of exercise can help:
- Improve individuals response to stress in the short term.
- Potentially lower their circulating stress hormones and return them to baseline levels.
- Reduce pro-inflammatory markers.
- Increase insulin sensitivity.
- Improve neurogenesis in the brain and counter-act the effect of circulating stress hormones on the brain.