Last month, both the BBC and Science Daily reported about the results of a new research which had been recently published on how 5 minutes of green exercise (also defined as activity done in the presence of nature) is great for mental health.
A great detailed analysis of the research – entitled ” What is the Best Dose of Nature and Green Exercise for Improving Mental Health? A Multi-Study Analysis” from Dr Joe Barton and Professor Jules Pretty, and published in Environmental Science and Technology in March 2010-, and its limitations can be found on the NHS UK website.
The following is an adapted extract of the latter.
Physical activity is known to be beneficial for health, including mental health but what is original in the research recently published by J Barton and J Pretty, that pooled the results of 10 studies from the University of Essex on the effect of outdoor exercise in green environments on self-esteem and mood, is that its aim is to determine the optimal dose of green exercise for obtaining the greatest improvement of self-esteem and mood.
The results of these 10 studies, carried out by the University of Essex over the past six years, representing a total of 1,252 volunteers, were pooled using standard methods. The data was analysed to find that optimal “dose” of green exercise (intensity and length) for producing the greatest improvements in mood and self-esteem. The researchers also looked at how the results were affected by the location of the exercise, the age, gender and mental health status of the individuals.
Volunteers included people already choosing to do green exercise (such as people in country parks, at national trust sites, urban flower shows or care farms), members of a local mental health association (Mind), allotment holders, young offenders and students. Exercise activities included walking, cycling, fishing, boating or sailing, horse-riding, farming activities and gardening.
Environments in which these activities took place included urban parks, countryside, farmland, forest and woodland, waterside areas and wild habitats. The 10 studies all looked at participants’ mood and self-esteem immediately before and after green exercise. They also all used the same commonly used measurement scales to assess self-esteem and mood.
The analyses looked at different durations of exercise:
- 5 minutes,
- 10-60 minutes,
- half day,
- or whole day.
Different exercise intensities were also examined. These were grouped as low (less than three metabolic equivalents [METs, a standard measure of exercise intensity], moderate (three to six METs) and vigorous (more than six METs).
What were the basic results?
The meta-analysis indicated that green exercise was associated with statistically significant improvements in self-esteem and mood, with slightly larger improvements seen in mood than self-esteem.
As the individual studies had found considerably different results for both of these outcomes, the researchers investigated this finding further. They carried out an analysis of the different groups and exercise types to see how the effect varied. For example, they carried out separate analyses of the type of green space, exercise duration or exercise intensity.
The researchers found that these improvements were greatest with five minutes of green exercise, with smaller benefits seen for longer exposures (from 10 minutes to a whole day). Light-intensity activity had the greatest effect on self-esteem; light activity and vigorous activity had similar effects on mood, with less effect seen for moderate activity.
All of the green environments had a positive effect on self-esteem and mood. The greatest effect was seen in environments that featured water, but the researchers say it was not clear whether its difference from other green environments was statistically significant.
Green exercise had a similar effect on self-esteem and mood for both men and women. People with self-reported mental health problems showed greater improvements in self-esteem with green exercise than those without such problems. But they showed no difference in improvements in mood. The improvements in self-esteem were greatest for people under 30, while the improvements in mood were greatest for those aged 31 to 70 years old. It was not clear whether the differences between the different age groups would be statistically significant.
The main limitations of this recently published research or meta-analysis, include:
- the fact that all the studies came from the same institution, and that more robust results may have been achieved by systematically searching for and pooling all research addressing the same question.
- the absence of control groups in all the pooled studies, so it is not clear whether these improvements would have occurred naturally over time, or if gym exercise or other leisure activities would have similar results.
- and the absence of evidence of what the long-term effects on these outcomes would be since the studies only measured mood and self-esteem immediately before and after exercise.
Links to the headlines
- ‘Green’ exercise quickly ‘boosts mental health’. BBC News, May 2 2010
- ‘In the Green of Health: Just 5 minutes of “Green exercise” optimal for good mental health’. Science daily, May 21 2010
Links to the study
Barton J and Pretty J. What is the Best Dose of Nature and Green Exercise for Improving Mental Health? A Multi-Study Analysis.Environmental Science and Technology, March 25 2010.