Super-Charging your HPA Axis: Natural Therapies Supported by Research Part III: Exercise

Your exercise routine influences multiple aspects of your body’s functions, including how to deal with stress.

Daily exercise benefits your body in multiple ways, well beyond losing that extra bit of body fat. Alongside with nutritious eating, regular exercise helps maintain a healthy heart, a strong immune system, and a sharp mind. For example, regular exercise has been shown to reduce the risk of neurological diseases and to protect the brain from the detrimental effects of aging, including protection against damage in cognition, brain function, and brain structure^1,2. Multiple studies support the protective role of exercise against Alzheimer’s disease through a beneficial effect on the levels of amyloid-β, a protein commonly associated with this disease^3-5. Likewise, studies have shown beneficial effects in other brain-related conditions, including dementia⁶, Parkinson’s^7-8 and Huntington’s disease⁹. Additionally, exercise has been shown to benefit various aspects of behaviour, including cognitive functioning, as well as, with affective, mood and emotional states^10-11.

A lesser-known beneficial effect of exercise is related to the way our body deals with stress. Multiple cellular mechanisms in your body are affected by regular exercise, including the chief system dealing with stress and depression: the Hypothalamic-pituitary-adrenal (HPA) axis. You can read an extensive and recent review on the topic here.

Exercise, stress and the HPA axis

Exercise can help mitigate the debilitating effects of stress, as supported by studies on salivary cortisol and alpha-amylase, two biomarkers commonly used as indicators of stress. In one study, levels of these two biomarkers were measured before and after acute exercise. Following the exercise bout, participants completed a stress test. The study found that individuals who experienced the greatest increases in exercise-induced cortisol and alpha-amylase showed the lowest physiological responses to stress¹².

Other studies have shown that acute exercise stimulates the HPA axis in an intensity-dependent manner. In other words, the more intense exercise you do, the more the HPA is stimulated. For example, studies report significant increases in the levels of cortisol secretion following intense exercise for 10 minutes or more^13-14. Following the exercise session, these high levels of cortisol are maintained for up to two hours. Cortisol is an important hormone that helps regulate our body’s response to stress or danger and has a myriad of other functions, including regulation of glucose metabolism, control of blood pressure and reduction of inflammation.

Your levels of cortisol can also influence learning and memory. The brain is filled with cellular receptors that recognise and bind to cortisol. In the brain, regions involved with learning and memory (e.g. hippocampus, prefrontal cortex and the amygdala) host a high density of these receptors. This means that high levels of cortisol will directly influence brain function, through its interaction with these cellular receptors¹⁵.

Maximizing exercise benefits

There is no doubt that increasing the time spent exercising will improve your health in multiple ways. Following an active lifestyle, however, should be complemented with lifestyle changes, including:

• Avoiding extended periods of time sitting. Multiple studies confirm that spending multiple hours per day sitting on a chair has a detrimental effect on your health. For example, excessive sitting has been suggested to double your risk of developing type 2 diabetes¹⁶.
• Eating a healthy diet, ideally, optimally designed by a dietician or other healthcare professional. This will ensure that you receive the optimal nutrients your body needs.
• Being mindful of your gut microbiota, and following habits that enhance their wellbeing.

Finally, before you jump on a treadmill, be sure to consult with your functional medicine or healthcare practitioner to ensure you do not have underlying conditions that need attention. A functional medicine practitioner can also help you identify the best nutritional pathway to follow in your search for optimal health. You should also consult with a movement professional about designing a plan that will help you exercise in a safe and effective manner.

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References

1. Kramer AF, Erickson KI, Colcombe SJ. Exercise, cognition, and the aging brain. Journal of applied physiology. 2006 Oct;101(4):1237-42. Read it!
2. Duzel E, van Praag H, Sendtner M. Can physical exercise in old age improve memory and hippocampal function?. Brain. 2016 Mar 1;139(3):662-73. Read it!
3. Murphy MP, LeVine H 3rd. Alzheimer’s disease and the amyloid-beta peptide. J Alzheimers Dis. 2010;19(1):311–323. doi:10.3233/JAD-2010-1221. Read it!
4. Brown BM, Peiffer JJ, Taddei K, Lui JK, Laws SM, Gupta VB, Taddei T, Ward VK, Rodrigues MA, Burnham S, Rainey-Smith SR. Physical activity and amyloid-β plasma and brain levels: results from the Australian Imaging, Biomarkers and Lifestyle Study of Ageing. Molecular psychiatry. 2013 Aug;18(8):875-81. Read it!
5. Wirth M, Haase CM, Villeneuve S, Vogel J, Jagust WJ. Neuroprotective pathways: lifestyle activity, brain pathology, and cognition in cognitively normal older adults. Neurobiology of aging. 2014 Aug 1;35(8):1873-82. Read it!
6. Lee HS, Park SW, Park YJ. Effects of physical activity programs on the improvement of dementia symptom: a meta-analysis. BioMed research international. 2016;2016. Read it!
7. Ahlskog JE. Does vigorous exercise have a neuroprotective effect in Parkinson disease?. Neurology. 2011 Jul 19;77(3):288-94. Read it!
8. Nelson LM. Physical Activity and Parkinson Disease Risk: An Intriguing Link. JAMA network open. 2018 Sep 7;1(5):e182633-. Read it!
9. Mueller SM, Petersen JA, Jung HH. Exercise in Huntington’s disease: Current state and clinical significance. Tremor and Other Hyperkinetic Movements. 2019;9. Read it!
10. de Asteasu ML, Martinez-Velilla N, Zambom-Ferraresi F, Casas-Herrero A, Izquierdo M. Role of physical exercise on cognitive function in healthy older adults: a systematic review of randomized clinical trials. Ageing research reviews. 2017 Aug 1;37:117-34. Read it!
11. Liao Y, Shonkoff ET, Dunton GF. The acute relationships between affect, physical feeling states, and physical activity in daily life: a review of current evidence. Frontiers in Psychology. 2015 Dec 23;6:1975. Read it!
12. Zschucke E, Renneberg B, Dimeo F, Wüstenberg T, Ströhle A. The stress-buffering effect of acute exercise: Evidence for HPA axis negative feedback. Psychoneuroendocrinology. 2015 Jan 1;51:414-25. Read it!
13. Hill EE, Zack E, Battaglini C, Viru M, Viru A, Hackney AC. Exercise and circulating cortisol levels: the intensity threshold effect. Journal of endocrinological investigation. 2008 Jul 1;31(7):587-91. Read it!
14. Kraemer RR, Blair S, Kraemer GR, Castracane VD. Effects of treadmill running on plasma beta-endorphin, corticotropin, and cortisol levels in male and female 10K runners. European journal of applied physiology and occupational physiology. 1989 Jul 1;58(8):845-51. Read it!
15. Heffelfinger AK, Newcomer JW. Glucocorticoid effects on memory function over the human life span. Development and psychopathology. 2001 Sep;13(3):491-513. Read it!
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17. Kramer AF, Erickson KI, Colcombe SJ. Exercise, cognition, and the aging brain. J Appl Physiol (1985). 2006;101(4):1237-42.
18. Duzel E, van Praag H, Sendtner M. Can physical exercise in old age improve memory and hippocampal function? Brain. 2016;139(Pt 3):662-73.
19. Vivar C, Adult hippocampal neurogenesis, aging and neurodegenerative diseases: Possible strategies to prevent cognitive impairment. Curr Top Med Chem. 2015;15(21):2175-92.