Green exercise for physical and mental well-being

Green exercise for physical and mental wellbeing

Physical activity has both physical and mental health benefits. 40% of the British population do not meet the recommended targets for physical activity 1, accruing an overall cost to our health services of approximately £8.3 billion 2. Green exercise is physical activity in the presence of natural environments 3. Green exercise delivers both the mental health benefits of physical activity and benefits of exposure to nature in a synergistic manner 3. Facilitated green exercise is therefore one form of Ecotherapy.

Physical activity imparts health benefits partly through a reduction of mean arterial pressure (MAP). Experiencing nature has been shown to independently reduce heart rate and blood pressure 4. It has been demonstrated that engaging in exercise of the same intensity, MAP was reduced to a greater degree when viewing pleasant rural scenes compared to viewing urban landscapes or in an exercise-only control 3. This effect has been seen even in childhood with an augmented post exercise hypotensive effect for children following green exercise compared to exercise alone 5. It has subsequently been suggested that reduced sympathetic activation, as measured by a reduction in urinary noradrenaline, might be responsible for these effects 6.

A study was performed showing the benefit of green exercise in those who are obese. With the increasing prevalence of vitamin D deficiency and the rise of rickets across the country 7, there is evidence which suggests that green exercise could act not only to enhance weight reduction in the obese, but also improve their skeletal stability. Obesity is associated with lower serum 25-hydroxyvitamin D, making the obese population vulnerable to metabolic bone disease. This is even more important considering the structural support excess weight demands. Research was conducted to consider whether associations were present between serum vitamin D levels, body mass index and outdoor exercise 8. Results showed that there was a significant reduction in hypovitaminosis in those who performed outdoor exercise. This implies that green exercise could have wider health benefits than initially conceptualised for the growing number of obese individuals in our population.

Outdoor exercise might also prove valuable in the synchronisation of sleep-wake cycles. One study investigated the effect of outdoor exercise on jet lag in cabin crew members 9. Urinary excretion of the 17-hydroxycorticosteroids (17-OHCS), catecholamine rhythm and sleep-wake patterns were analysed in cabin members before, during and after travelling an 8-hour time difference. Samples in the intervention group, who exercised for 5 hours outside on the day after travel were compared to control cabin members who shopped and rested in their rooms. Results suggested that there was a significant increase in the rate of resynchronisation of circadian rhythm following outdoor exercise compare to those who remained indoors. This implies that green exercise could be beneficial for all travellers, but particularly those who are frequently having to shift their body clocks.

Not only is there evidence supporting the use of green exercise to promote health in the adult population, there is growing evidence that exposure to nature has significant health benefits young people. A natural environment can act as an incentive to exercise for children 10. One challenge will be the reluctance of today’s children to experience nature, with only 10% of them regularly accessing nature compared to the 40% that today’s adults did when they were young 11. This is even more problematic since the time spent in outdoor environments positively correlates with amount of physical activity 12. However, evidence implies that exercise is perceived as less intense if undertaken outdoors 13 and that when in a natural environment people can walk faster with a paradoxically lower rating of exertion when compared to indoor activity 14. By increasing the intensity at which one can pleasurably exercise the benefits of undertaking physical activity might increase, and the beneficial effects of exercise on health may be seen earlier.

Mental illnesses are a major health issue. The World Bank estimates that in 2020 depression alone will be the second most common cause of disability in the Western World 15. The financial impact of mental health problems to the English economy is estimated at £105 billion per year 16. It has been suggested that green exercise could be offered as an alternative or adjunct to traditional antidepressant drugs in the treatment of depression 17. Furthermore, since approximately 21% of general practitioners prescribe exercise in the management of depression 18, the enhanced efficacy of exercising in nature presents green exercise as a potential development in the support available for this common disabling disease. The evidence supporting the efficacy of green exercise as a therapeutic intervention for mental health diagnoses is expanding. Walking in green space has a greater positive effect on self-esteem and mood than walking indoors 19. MacKay et al., showed that green exercise significantly reduces anxiety states, with the effect being correlated with how ‘green’ the environment is 20. This implies that ‘green prescriptions’ could be used not only to endorse weight loss and physical health, but also be utilised as a resource in the treatment of mental health issues.

A meta-analysis of the supporting evidence of the efficacy of green exercise on mental health outcomes was undertaken in an attempt to elucidate the most effective form, intensity and duration of activity 21. Even short periods of green exercise (the first 5 minutes) generated large benefits, with the dose response still positive (yet with diminished returns) for longer periods. The same was true for the intensity of activity undertaken. Every form of green exercise displayed positive outcomes on self-esteem and mood. Statistically equivalent benefits to self-esteem through green exercise was noted in both males and females. Importantly those with pre-existing mental health issues experienced greater benefits than healthy participants.

Not only does exercise provide the opportunity to support mental health issues in the young, it also has potential as a therapeutic intervention for dementia. There have been many observational studies concluding that physical activity reduces cognitive decline and whilst green exercise aids the cognitive ability of those living with dementia, it improves their physical wellbeing. It has been demonstrated that sleep 22,23, continence 22 and mobility 24 are all improved when dementia patients undertake green exercise. In a paper discussing risk factor reduction in Alzheimer’s disease it was postulated that reducing physical inactivity by 25% could prevent as much as one million cases of dementia worldwide 25. It has been demonstrated that aerobic exercise leads to an increase in hippocampal volume in healthy older adults living in the community 26

Therefore, we can use natural environments to enhance the mental health of our population whilst potentially reducing the financial burden on our health and social services. The ‘Biophilia Hypothesis’ suggests that human desire for nature is innate 27 – we did, after all, evolve from wild primates. With this genetic ancestry designing us to be exposed to nature, being deprived of this ingrained need might fundamentally shift the equilibrium within us, leading to both physical and mental disease.

So get outside for your exercise! The British Society of Lifestyle Medicine have a great #1change campaign, I feel taking your exercise outside could be a great place to start and be the first thing your change for a healthier lifestyle.

 

References:

  1. Department of Health. Start Active , Stay Active. (2011).
  2. Department of Health, Physical Activity, H. I. and P. At Least Five a Week- Evidence on the impact of physcal activity and its relationship to health. Nutr. Bull. 29, 350–352 (2004).
  3. Pretty, J., Peacock, J., Sellens, M. & Griffin, M. The mental and physical health outcomes of green exercise. Int. J. Environ. Health Res. 15, 319–37 (2005).
  4. Laumann, K., Gärling, T. & Stormark, K. M. Selective attention and heart rate responses to natural and urban environments. J. Environ. Psychol. 23, 125–134 (2003).
  5. Duncan, M. J. et al. The effect of green exercise on blood pressure, heart rate and mood state in primary school children. Int. J. Environ. Res. Public Health 11, 3678–88 (2014).
  6. Li, Q. et al. Acute effects of walking in forest environments on cardiovascular and metabolic parameters. Eur. J. Appl. Physiol. 111, 2845–53 (2011).
  7. Pearce, S. H. S. & Cheetham, T. D. Diagnosis and management of vitamin D deficiency. BMJ 340, b5664 (2010).
  8. Florez, H., Martinez, R., Chacra, W., Strickman-Stein, N. & Levis, S. Outdoor exercise reduces the risk of hypovitaminosis D in the obese. J. Steroid Biochem. Mol. Biol. 103, 679–81 (2007).
  9. Shiota, M., Sudou, M. & Ohshima, M. Using outdoor exercise to decrease jet lag in airline crewmembers. Aviat. Space. Environ. Med. 67, 1155–60 (1996).
  10. Gladwell, V. F., Brown, D. K., Wood, C., Sandercock, G. R. & Barton, J. L. The great outdoors: how a green exercise environment can benefit all. Extrem. Physiol. Med. 2, 3 (2013).
  11. Marketing, E. Report to Natural England on childhood and nature: A survey on the changing relationships with nature across generations. 32 (2009).
  12. Cleland, V. et al. A prospective examination of children’s time spent outdoors, objectively measured physical activity and overweight. Int. J. Obes. (Lond). 32, 1685–93 (2008).
  13. Ceci, R. & Hassmén, P. Self-monitored exercise at three different RPE intensities in treadmill vs field running. Med. Sci. Sports Exerc. 23, 732–8 (1991).
  14. Focht, B. C. Brief walks in outdoor and laboratory environments: effects on affective responses, enjoyment, and intentions to walk for exercise. Res. Q. Exerc. Sport 80, 611–20 (2009).
  15. Bank, W. World Development Report 1993. (The World Bank, 1993). doi:10.1596/0-1952-0890-0
  16. Centre for Mental Health. The economic and social costs of mental health problems in 2009 / 10. 1–4 (2009).
  17. Samson, C. & Pretty, J. Environmental and health benefits of hunting lifestyles and diets for the Innu of Labrador. Food Policy 31, 528–553 (2006).
  18. Mental Health Foundation. Moving on up. (2009).
  19. Mind. Ecotherapy – the green agenda for mental health Key findings Green exercise at local Mind groups. (2007).
  20. Mackay, G. J. & Neill, J. T. The effect of “green exercise” on state anxiety and the role of exercise duration, intensity, and greenness: A quasi-experimental study. Psychol. Sport Exerc. 11, 238–245 (2010).
  21. Barton, J. & Pretty, J. What is the best dose of nature and green exercise for improving mental health? A multi-study analysis. Environ. Sci. Technol. 44, 3947–55 (2010).
  22. Brooker, D. J., Woolley, R. J. & Lee, D. Enriching opportunities for people living with dementia in nursing homes: an evaluation of a multi-level activity-based model of care. Aging Ment. Health 11, 361–70 (2007).
  23. Connell, B. R., Sanford, J. A. & Lewis, D. Therapeutic Effects of an Outdoor Activity Program on Nursing Home Residents with Dementia. J. Hous. Elderly 21, 194–209 (2007).
  24. De Bruin, S. R. et al. Day care at green care farms: a novel way to stimulate dietary intake of community-dwelling older people with dementia? J. Nutr. Health Aging 14, 352–7 (2010).
  25. Barnes, D. E. & Yaffe, K. The projected effect of risk factor reduction on Alzheimer’s disease prevalence. Lancet Neurol. 10, 819–28 (2011).
  26. Erickson, K. I. et al. Exercise training increases size of hippocampus and improves memory. Proc. Natl. Acad. Sci. U. S. A. 108, 3017–22 (2011).
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