Litter-picking is the new get-fit.
Members of the Cardiff Rivers Group suggest taking part in a community clean-up can burn off more calories than playing a round of golf.
The health benefits of junk-clearing were discovered by a volunteer who took part in an event organised by the group earlier this month.
Volunteer Nigel Barry, of Llanishen, Cardiff, wore a heart monitor to calculate the number of calories he burned during the litter-pick.
He found that two hours of light litter-picking duties burned off 620 calories - eight more calories than playing the same amount of golf.
Mr Barry said: "I would encourage people to take part in litter-picking as it's a great form of exercise, improves the environment and you even get thanked by passers-by for your efforts."
The health link was made while Cardiff Rivers Group members litter-picked the banks of the River Taff.
The 27 volunteers collected rubbish from the riverbanks and surrounding woodlands, collecting 35 bags of rubbish, 120kg of metal, a motorbike, seven trollies, a beer barrel, 12 road cones and a space hopper.
All of the rubbish was disposed of by Cardiff council's parks department.
Louise Tambini, of Cardiff Rivers Group, said: "It was another successful event with a fantastic turnout. I was astonished so many people came out on a rugby international day, and even more astonished with how much rubbish we collected.
"I'd like to thank everyone who gave up their morning to help and a special thank you to McDonald's for providing drinks to all the thirsty volunteers and Cardiff council for collecting the rubbish."
To take part in Cardiff Rivers Group, call Louise on 07824 504790 or e-mail louise. firstname.lastname@example.org