Going for a run outdoors is better than exercing in the gym because it has a positive impact on mental, as well as physical health, researchers have found.
A study found that exercise in natural environments was linked to greater feelings of revitalisation, increased energy and positive engagement.
Levels of tension, confusion, anger and depression were found to be lowered by exercising outside.
A team at the Peninsula College of Medicine and Dentistry looked at data from sources including eleven trials involving 833 adults.
All compared the relative merits of outdoor exercise compared to indoors.
As well as improved mental health benefits, those studied also reported greater enjoyment from exercising outside, and a higher likelihood of continuing with the exercise regime.
Research fellow Dr Jo Thompson-Coon said: "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."
Professor Michael Depledge, senior author of the study, which was published in the journal Environmental Science and Technology, added: "Some 75 per cent of the European population now live in urban environments, so that increasing efforts need to be made to re-connect people with nature.
"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."