The coronavirus lockdown has spurred thousands to put on trainers and run.
More than 858,000 people downloaded the NHS-backed Couch to 5K app between March and the end of June.
The figures represent a 92% increase over the same period in 2019, when it was downloaded 448,000 times.
The NHS has urged people to keep going if they started exercising during the lockdown and hailed running as good for physical and mental health.
It comes after Prime Minister Boris Johnson this week described the UK as fatter than its European neighbours and as he considers policies to get Britain moving.
The app, known as One You Couch to 5K on the Apple App store and Google Play store, aims to equip people who have never run consistently before with the stamina to tackle a 5000m (3.1 mile) circuit over nine weeks.
A roster of coaches - including radio DJ and Sport Relief participant Jo Whiley, comedians Sarah Millican and Sanjeev Kohli, and former US Olympic sprinter Michael Johnson - help motivate beginners.
There is also the option to listen to Laura, a less well-known narrator who is also the voice of the Couch to 5K podcast.
Their voices guide runners every step of the way, imparting wisdom and tips.
Bristolian Rob Bryher, 36, marked his completion of Couch to 5K with a celebratory tweet on Monday.
He said: "I downloaded the app in mid-April and in the beginning I just didn't think I'd complete it. I'm one of these people who starts lots of things and can be put off if something doesn't go right.
"I went with Jo Whiley because I used to listen to Radio 1 in the 90s - she was comforting and had a bit of humour to her.
"Because of the lockdown I couldn't, you know, go to the pub," he laughed. "I just wanted to do something that got me out."
James Sharp, 33, from Essex, described his progress after five weeks of using the app.
"It's going really well," the NHS marketing manager said. "For me I was thinking I should practise what I'm preaching. I've also been diagnosed with blood pressure hypertension and I was looking for things to reduce that and one of them is exercise.
"I'm not a sporty person at all, six weeks ago I couldn't run more than 60 seconds and now I'm at seven and eight minutes without stopping."
He added that people should just trust the programme. "Stick with it, it does work," he said, adding he's found the exercise has also improved his mental health.
Amateur rugby player Louise Banks, 44, from Kent, said her teammates set up a Couch to 5K group during lockdown - and now she can run 5.6 km in half an hour.
"I wanted to do something that had a long-lasting impact. I'd never properly run - in rugby you stop and you start."
"I've got asthma and fibromyalgia and I thought it would only be good to improve my health in the long run," she added.
"The first couple of weeks were a nice introduction and then suddenly it ramps up. I found myself having to repeat a week before moving on. I used Jo Whiley and found the things she says really resonate with me."
Dr Nikki Kanani, NHS national director for primary care, who has also been running more during lockdown, said: "We have all coped differently during lockdown, and for me, running and taking some time out to exercise with my children has been really important - we've seen huge benefits physically, mentally and for our general wellbeing."
Rosanna O'Connor, acting director for health improvement at Public Health England, said: "Lockdown has been challenging for us all but it's hugely positive to see so many people using this opportunity to get more active and using Public Health England's app, part of its Couch to 5K campaign.
"Keeping active is not only good for our physical health but also crucially at this time helping us look after our mental health. And staying fit and healthy means we're also playing our part in supporting the NHS."