The BBC reports on a new study which reveals outdoor exercise delivers an estimated £2.2bn of health benefits to adults in England each year,
Scientists calculated that more than eight million people each week took at least 30 minutes of "green exercise".
They hope the results highlight how encouraging more people to use parks will help reverse the trend of rising obesity levels across the UK.
The findings have been presented in the journal Preventative Medicine.
"What we look at here is something that can be converted relatively simply into monetary values," explained lead author Mathew White from the European Centre for Environment and Human Health at the University of Exeter.