If you're out and about on the streets of Sheffield, you'll no doubt see countless runners pounding the pavements of the city with seven hills.
But there is one group of runners who might particularly catch your eye - and it's not because they're in fancy dress.
They'll probably stand out because of how slow they run at - but they have a very valid reason.
Runners Against Rubbish was set up by Stuart Walker in November 2016 and the group has one aim - to tidy up the streets of Sheffield and surrounding routes.
Engineering researcher Stuart said: "I was out on my bike one day and I was shocked at the amount of litter on the streets and I thought I'm going to do something about it.
"When you go a bit slower you see all the rubbish that you know has been dropped by runners like energy gel wrappers, which gives us a bad name.
"I just thought I wanted to do something about it. You are never going to get the people who drop the litter to change because they are so far from it but what we are trying to do is put pressure on so that everybody think it's unacceptable to drop litter and encourage people to pick it up when they see it."
Members of RAR collect rubbish while they run, helping to keep the city cleaner for others and Stuart said it had no impact on his training for races.
They even hold regular 'races' where the winner is often the runner who has collected the most litter rather than the first to cross the finish line.
Stuart added: "I run a lot - usually twice a day so what I usually do is runs I'll stop and pick litter up during my easier runs and then I'll run to a target time or pace on the way back because it's hard to just run past rubbish."
The group already has more than 200 members and they're not just based in Sheffield. Stuart now has runners signed up across the country - from the far north of Scotland to the South Devon coast.
And it is the southern coast which is the site for the group's first ambitious project. Runners Against Rubbish will hold a Pick the Path event on the South West Coast Past, which runs from Minehead in Somerset to Poole in Dorset.
The race will be held from Friday, July 27 to Sunday, July 29 and will cover all 630 miles of the country's longest National Trail.
Stuart said: "We'll need something like 30 teams of two to ensure that some runners are continuously running for the full three days and we only launched it on Monday and have already had about 15 people sign up.
"I'm really looking forward to it - it should be a great weekend and I just can't believe the support I've had. It's been incredible."
For more information on Runners Against Rubbish or to find out more about the Pick the path event visit www.runnersagainstrubbish.org.