Media playback is unsupported on your device Media caption Battle to reach the start line

For the first time in the event's 17 year-history, more women than men lined up at the start line of the Cardiff Half Marathon.

A record 27,500 runners are taking on the third biggest running event in the UK on Sunday.

More than half are women, including Helen James, of Caerphilly, who is running 13.1 miles for the first time.

Inspired by watching a friend, the 34-year-old has lost 12 stone since taking up running.

When Helen lined up at the start with her number pinned to her running vest, it marked the final leg of a remarkable journey.

It began when she was stood watching - slightly enviously - a friend complete the challenge four years ago.

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It was all the motivation she needed to change her life and improve both her physical and mental health.

She joined a gym and still remembers the smile on her face the first time she managed to run around the block as a warm up. From there, she joined Caerphilly Runners running club.

"Only a couple of years ago I would never have imagined I would even get to the start line," she said.

"Sometimes the things worth having don't come easily. It's all about challenging and improving yourself.

"I still find running challenging but the buzz I received from running made me realise I could do anything. It gives me an enormous sense of wellbeing.

"I feel more energetic throughout the day, I sleep better at night and feel more relaxed and positive about myself and my life. Exercise has also made me a lot more resilient.

"I'm really excited, there's such a camaraderie in running.

"Crossing the line will bring many emotions but it will be a really great example to myself of what I can achieve when I set my mind to it and work with supportive and kind people."

Image copyright Huw Evans Agency Image caption Claire Sanderson has used running to cope with depression

For so many others taking part, it has been a battle just to make the start line.

Born in Abercynon, Claire Sanderson is editor of Women's Health magazine and has used running to cope with depression and anxiety.

Her experience inspired her to spearhead a Run Wales scheme to help 100 novice female runners take on the Cardiff Half Marathon for the first time.

"It was after I was hospitalised during my 20s that I decided to prioritise nutrition and moving my body more," she said.

"Many of these women have come through similar experiences, overcoming cancer, obesity, deprivation, post-natal depression.

"There are so many amazing stories how they are using exercise to better themselves and hopefully they are inspiring friends, family and their children."

The National Survey of Wales in 2017-18, which interviewed more than 11,000 adults, found 27% of women took part in sport three or more times a week last year.

It was a 1% rise on the previous year but Sport Wales chief executive Sarah Powell said the body "needs to invest at a younger age" to increase the involvement of girls and women in sport.

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There was a 9% rise in female runners in 2018 and this year they will make up 51% of the total entry.

A lack of free time remains the biggest barrier to women taking part in physical activity, according to research by Cardiff University.

Dr Sara Macbride-Stewart said women's leisure time is often squeezed by balancing the demands of work and family.

"We need to make society more supportive so women's exercise time doesn't get lost in the push between work and family life. How can we make it sustainable?" she said.

"In winter, often women don't feel comfortable in the places they like to run, in parks and trails away from traffic.

"However the emergence of social running clubs has also been a real positive for women, enabling them to run together in supportive ways."

South Wales Police launched a campaign to coincide with National Running Day in June targeting anti-social behaviour directed at people exercising.

Image copyright Getty Images Image caption Olympian Helen Jenkins is also taking part

Finding time to exercise even affects those who have been at the very top of their sport.

Two-time world triathlon champion and Olympian Helen Jenkins, 35, of Bridgend, hopes to run the event for the first time, five months after giving birth to her second child.

"When you're a parent, you have a lot less time to yourself to exercise. For me it's my escape and I'm a lot better when I come back home," she said.

"It has been great to have this as something to aim for and enjoy. It's a lot more relaxed when you're not worrying about finishing positions.

"It's a real positive for the women's health movement to see so many women running this event.

"There are more barriers for women and girls than boys. The drop-out rate in sport among girls, especially around the 14/15 age, is very high but perhaps we're now seeing women coming back to sport at a later age and running for fun and fitness rather than competition."

Live coverage of the Cardiff Half Marathon is on BBC One Wales from 09:30 and BBC Two network at 09:45. Highlights will be on BBC Two Wales at 22:00 and on the BBC iPlayer.