Twenty open-air gyms constructed partially from melted down knives taken off the streets will be created in areas hit by violent crime.
The gyms, created by charity Steel Warriors and funded by supermarket Co-op, will be free to use and organisers hope they will form community spaces.
As part of the multimillion pound project, two new gyms will be built this year.
The gyms will include instructors who will provide training sessions for different abilities and will work to try to improve physical and mental well-being within communities.
Co-op, which recently stopped selling single pack knives in their stores, is helping Steel Warriors to have a trainer at each gym but local training instructors, sports groups and youth groups will also be invited to use the gyms for free.
London has been in the grip of a knife crime crisis in recent years, but earlier this month the Met Police reported the number of killings in London is down by a quarter and injuries from stabbings among under-25s has fallen by 15%.
Metropolitan Police Commissioner Cressida Dick credited a 30% increase in stop and searches for the drop in violent crime in the capital.
Figures published last month showed police in England and Wales recorded 40,829 offences involving knives or sharp objects in 2018, the highest number since comparable data started in 2010/11.
Steve Murrells, CEO of Co-op, said: “Community spaces have such an important role to play in fostering community spirit and the loss of youth centres and spaces has had a negative impact. This is something unique which makes a positive difference to communities.
“It literally adds steel to communities which are rallying against problems like knife crime by taking the weapons off the streets and turning them into street gyms.”
Steel Warriors worked with the Met Police to make gym equipment using the metal from melted-down knives and blades, allowing them to open a gym in Tower Hamlets, London, in 2017.
Sky News visited the gym shortly after it opened.
The gym consists of several metal climbing frames, gymnastic beams and parallel bars, ideal for bodyweight resistance exercises like callisthenics.
“Knives are in the very DNA of the gym,” Steel Warriors founder Ben Wintour told Sky News.
“If it was just a normal gym people wouldn’t necessarily talk about the (knife crime) issue, but because it’s built into the gym itself, it gets people talking about it.”
Now, almost two years on, Daniel Rose, director of a nearby youth centre, said: “From day one people have been using it. Kids doing their usual exploring and games, older women in their hijabs, this area has a big Bengali population, using it for a daily workout in the morning.
“The whole community has embraced it, even if it’s just to test it out for a few minutes. Young people who are into this kind of thing have set up their own clubs. A lot of people are also filming vlogs and workout demonstrations.”
It comes as a nationwide campaign was launched last week to provide 21,000 community sports coaches with training to improve the mental health of children and teenagers.