Cycling is just a hobby to many, but for others the battery power of an e-bike has transformed their lives - enabling them to cycle when they otherwise couldn't, find new career paths and improve their mental health.
'It gave me a second chance'
Cycling was everything to Tim Gregory. As a teenager, he founded the Norwich Flyers BMX club and was at the forefront of Norwich getting its national public access BMX track at Sloughbottom Park, a project he describes as his "baby".
But 10 years ago, a lung condition "ruined his life". Doctors told him he had two years to live and he began using an oxygen tank to manage the disease. He says about 75% of his lung surface became scarred from fibrosis.
Tim, who had ridden since the age of 13, gave up cycling as he struggled to breathe.
"If you could imagine riding your bike with a tennis ball in your mouth and how that would affect your breathing then you're getting there."
Giving up his lifelong hobby at 41 meant he spent less time with his friends, started suffering from depression and had a breakdown.
When a friend recently suggested he tried an e-bike, the now 51-year-old initially turned his nose up at the idea but now admits it "completely changed my life".
"With the illness and having had to give up cycling, my life came tumbling down.
"So to be able to ride again, and ride with my friends again, meant the world to me - it felt like I had been given a second chance at life."
Since that eye-opening first ride with his friends, Tim has bought an e-bike and enjoyed riding off-road trails with people he has not been able to cycle with in 10 years.
He has even switched careers as a result and now sells e-bikes to help others like him.
"I thought, 'I've got my cycling back, I've got a new life' - if [an e-bike] has done this for me it can do it for other people."
'It's given me confidence'
Kara Beal, 21, was used to filming her boyfriend Tom Cardy doing stunts on his mountain bike for his social media channels - but she never thought it was something she could do herself.
When he was given an opportunity to ride an e-bike, he encouraged her to have a go too. Within a few months, the critical care nurse had gained the confidence to pedal up Snowdon and has now entered her first competitive e-bike race.
"I would never have done it without an e-bike," says Kara. "The weight of the bike helps me with big rocks and even though it's heavy for down-hilling, it makes me feel more stable on the bike.
"It's really cool, I just love it and I don't think about going to a non e-bike."
It has also opened up opportunities for her. Since she started to ride an e-bike, she has set up a YouTube channel, documenting her trials and tribulations on camera. Her videos get thousands of views, with people commenting on her improved skills.
"Before mountain biking, I didn't really have a hobby. I used to go to the gym and I did bit of Thai boxing, but nothing I wanted to do all the time," says Kara, from Crawley in West Sussex.
"Riding the e-bike has given me a lot more confidence. I would only ride with Tom at first but when I gained more confidence, I started to go to places on my own so I can practise and get better.
"I love it and it's become part of my life."
'Riding an e-bike isn't cheating'
- Electrically assisted pedal cycles, also known as pedelecs, are standard pedal cycles fitted with a battery and electric motor
- When you pedal, the motor kicks in to take some of the strain
- Under regulations in England, Scotland and Wales, they must have a maximum power output of 250 watts and top speed of 15.5mph (25kph)
- Prices range from just under £400 to £5,000
- According to Halfords, up to 60,000 e-bikes are sold in the UK a year, compared to three million bikes
- Olympian Chris Boardman said 30% of people who buy e-bikes from his range wouldn't have bought a bike otherwise. He says they are no longer seen as "cheating" at cycling
- The first Union Cycliste Internationale electric mountain bike world championships were held on 28 August and 50 people took part
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'Prescribe them on the NHS'
For Dom Thompson, an e-bike has helped transform her health.
She says she got back from a walking holiday in Scotland in September 2015 and remembers thinking how difficult it had been just to walk.
"I was fat, unfit and smoked, I was having a rough time with menopausal symptoms and decided I had to do something before I ended up as a statistic and possibly dead too early," says the 55-year-old nurse from Telford, Shropshire.
On their return, she and her husband each bought a bike. But, although she found cycling enjoyable, she says it was very hard work and she stopped, using excuses such as it's "too cold or too wet or too windy".
Her husband researched mountain e-bikes and since buying a pair, the couple have "never looked back".
Dom says she is riding more miles, setting harder goals and tackling tougher terrain, which has given her "confidence in more ways than one".
The mother of two says she's also been spending more time with her husband and they have both lost weight. She has even bought a second e-bike.
"I can't tell you how it helps my mental health; even in the depths of despair, I get out my bed and get out on the bike. It should be prescribed on the NHS," she says.
"This is what I call my mid-life crisis: two e-bikes, got my hair cut short and dyed purple and then got a tattoo - I finally plucked up the courage to do what I'd been wanting to do for years."