Green exercise, Part Two

Last May I posted a blog on the health benefits of exercise in natural environments (also called 'green exercise'), featuring new research on the subject. Since then, two systematic reviews on the topic have been published, the most recent just last week, so as some wet, grey weather is currently making it harder to leave the warmth of the office for a lunchtime walk in CABI's own green surroundings, maybe it's time to revisit the topic to remind myself of the possible benefits.

The most recent review comes from a team at the Peninsula College of Medicine and Dentistry in Devon, UK. The authors analysed existing studies and concluded that there are benefits to mental and physical well-being from taking exercise in the natural environment. Their findings are published in the research journal Environmental Science and Technology on February 4th 2011.

The team analysed data from a number of sources including 11 randomised and non-randomised control trials incorporating information from 833 adults. Eligible trials were those that compared the effects of outdoor exercise initiatives with those conducted indoors and which reported at least one physical or mental well-being outcome in adults or children.

The study found that most trials showed an improvement in mental well-being: compared with exercising indoors, exercising in natural environments was associated with greater feelings of revitalisation, increased energy and positive engagement, together with decreases in tension, confusion, anger and depression. Participants also reported greater enjoyment and satisfaction with outdoor activity and stated that they were more likely to repeat the activity at a later date.

However, none of the identified studies measured the effects of physical activity on physical well-being, or the effect of natural environments on sticking to exercise.

On balance the authors say that the review identified some promising effects on self-reported mental well-being immediately following exercise in the natural environment, as opposed to those reported following exercise indoors.

Dr. Jo Thompson-Coon, the first-named author, commented: "The hypothesis that there are added beneficial effects to be gained from exercising in the natural environment is very appealing and has generated considerable interest. By using the data currently available to us we have added strength to the link between mental and physical well-being and outdoor exercise, but further research and longer, tailor-made and focused trials are needed to better understand this link."

The senior author of the study, Professor Michael Depledge, added: "Some 75 per cent of the European population now live in urban environments…..our research, which brings together data from a wide variety of sources, adds significant weight to the case for spending more time in the natural environment as members of the public and their clinicians fight to counteract the negative outcomes of modern living, such as obesity and depression. We look forward to conducting the further research and trials required to establish the evidence-base for introduction of outdoor activity into general lifestyle to complement therapeutic intervention."

A previous systematic review (Bowler et al. 2010) also examined studies which compared the effects of short-term exposure during a walk or run to 'natural' environments (including parks and green university campuses) compared with indoor or built-up environments. In 25 studies included in the review, the most common outcome measures were scores of different self-reported emotions. Based on these data, a meta-analysis provided some evidence of a positive benefit of a walk or run in a natural environment in comparison to a synthetic environment. The authors conclude that the studies are suggestive that natural environments may have direct and positive impacts on well-being, but support the need for investment in further research on this question to understand the general significance for public health.

Of course, it's fairly common that a main conclusion of such reviews is that more research is needed – future funding could be at stake! Both studies are somewhat critical of the standard of much of the work done so far, with Thompson Coon et al. commenting that "the interpretation and extrapolation of these findings is hampered by the poor methodological quality of the available evidence". Bowler et al. point out that the studies they reviewed were based on very short-term effects of different environments, and that the most common participants were physically active male college students, so not representative of the wider population.

The more cynical among us may view research into green exercise as spending time and money on studying something that seems self-evident; that being in attractive natural surroundings, including while exercising, lifts the mood. But with various programmes around the world using public funds for promoting physical activity in the outdoors partly for mental and physical health benefits – the Green Gym and Blue Gym [which coincidentally is an initiative of the Peninsula Medical School, where the latest systematic review comes from] programmes in the UK are examples of this - it is important to back proposals for funding with hard evidence of benefits. For the rest of us, it's a simpler equation – if a walk or run in the outdoors makes you feel better, get out there and do it!

References

J. Thompson Coon, K. Boddy, K. Stein, R. Whear, J. Barton, M. H. Depledge. Does Participating in Physical Activity in Outdoor Natural Environments Have a Greater Effect on Physical and Mental Wellbeing than Physical Activity Indoors? A Systematic Review. Environmental Science & Technology, 2011; DOI: 10.1021/es102947t

Bowler, D. E.; Buyung-Ali, L. M.; Knight, T. M.; Pullin, A. S. A systematic review of evidence for the added benefits to health of exposure to natural environments. BMC Public Health, 2010, 10, 456, (4 August 2010), 57 ref.

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