"If I quit, everybody's going to believe women can't do this."

That's the thought that latched itself into Kathrine Switzer's head when a male official tried to push her off the course of the Boston Marathon in 1967.

At just 20 years of age, Switzer had registered for the event after months of training, deciding she was ready to tackle the ultimate distance run.

She had registered for the event as "K.V. Switzer", a gender-neutral name she says wasn't intended to mislead officials — it was habit, the same way she signed off her college papers.

By the end of the race Switzer says she had "a life plan laid out in front of me". ( Supplied: Brearley )

In fact, Switzer showed up at the start line wearing lipstick and eyeliner — the first woman to do so as a registered athlete.

(Switzer wasn't the first woman to run the Boston Marathon — Bobbi Gibb ran, unregistered, the year before.)

But just two miles into the race, Switzer was accosted by Jock Semple, a race official who grabbed her and tried to pull her off the course.

Recalling the moment, Switzer says: "There's this split second where you say, 'Oh my God, I've done something really wrong, I'm so scared, I'm so ashamed'."

"Then all of a sudden I said, 'no, no, if I quit, everybody's going to believe women can't do this'."

And by the end of the race — she crossed the finish line at 4 hours and 20 minutes — Switzer had what she calls "a life plan laid out in front of me".

"You get to about 35km and you can't be angry or afraid anymore, it all goes away … I was no longer angry with the official and I was just totally determined to finish," she says.

"I had a long time to think about why this official had done that and I went through the whole thing of murdering him every way a person could be murdered and I realised he was an overworked, angry race director."

Kathrine Switzer at the 1967 Boston Marathon, shortly after being attacked by Jock Semple. ( Supplied: Brearley )

Switzer says she then "got angry with the women" for not racing, before realising she was being "really stupid" and forgetting they didn't have the positive reinforcement and coaching team that had made the difference for her.

"It became the focus of my life to create those opportunities," she says.

"I wanted to do it, I knew it could help women and I knew women deserved it."

So, that's what she did.

'If I can do that, how much talent is out there?'

Perhaps the most significant of Switzer's achievements was her role in having the women's marathon added to the Olympics in 1984 — almost 90 years after the men's event.

By 1970, she had returned to Boston — "1968 and 1969 I was still very afraid of Jock Semple" — and would do so for the next eight years, running her best time of 2:51 in 1975.

Although Switzer came second to Liane Winter in that race, who ran a world record time of 2:42, her time was the third-best in the US and the sixth-best in the world, at the time.

Switzer ran her best time of 2 hours and 51 minutes at Boston in 1975. ( Supplied: Jeff Johnson )

"I had a real chip on my shoulder because everybody said, 'you're just a jogger', and that really upset me," Switzer says.

"I knew I wasn't a really talented athlete but I also can work really hard and when I worked hard and got down to 2:51, that's when I really realised, if I can do it, anyone can do it.

"That's when my dream to get the women's marathon at the Olympics became a reality because I said, 'If I can do that, how much talent is out there? Real talent? What could women do if they only had this in the Olympics?'"

After her eighth Boston Marathon, an opportunity arose to help Switzer bring that dream to fruition.

As director of the Women's Sports Foundation, she was invited to create a global series of races with Avon Cosmetics on board as a sponsor.

"They believed in what I wanted to do — to organise this global series of races and use those of leverage with the International Olympic Committee," Switzer says.

"I thought, never in a million years is anybody going to sponsor this, because it was really out there, as it would have been — of course, this is 1976.

"I've got to tell you, it was 24-7 work. I was just flat out because I eventually had 400 races in 27 countries for over a million women."

Switzer ran the 1972 Boston Marathon, the first year women were officially allowed to compete. ( Supplied: Jeff Johnson )

It was the data and statistics from those hundreds of races that led to the women's marathon finally making it to the 1984 Summer Olympics in Los Angeles.

"We had all the international representation, the numbers, and the talent, and even the medical evidence to show them," Switzer says.

Returning to run Boston 50 years later

It's an achievement Switzer is still extremely proud of.

"I thought that would change the world, and in many ways it did," she says.

"People around the world saw it on television in 1984 and said, 'woah, women are suddenly running 42.2km, are you kidding me?'

"I thought seeing that on television would change a lot of minds, and it did — millions and millions."

Switzer has done the television broadcast of the Boston Marathon for the past 37 years. ( Supplied: Reebok )

But between all those races across the world, the Boston Marathon — and the city itself — has remained an integral part of Switzer's life.

She has done the television broadcast of the event for the past 37 years — starting the year after she ran it for the last time.

"When I do go back to Boston, I always take a walk across the finish line and I swear to you, I start sweating and my heart starts beating really hard," she says.

"I tell you, the heart goes pitter-pat, no question about it."

But this year — 50 years after she first ran and 45 years after women were officially allowed to enter — Switzer will run the Boston Marathon once again.

Switzer will run the Boston Marathon again, 50 years after she first ran. ( Supplied: Hagen Hopkins Photo )

She says revisiting Boston is a way of honouring what women, and Switzer herself, have achieved since 1967.

"I'm 70, I'm in good shape, I've run all my life, and I'm thrilled with my body," she says.

"It's a great way to celebrate the incredible achievements women have made in the last 50 years.

"To go from being a person where an official tried to throw me out of a marathon because I was a girl to now the fact there are more women runners in the US than men … is a phenomenal statement about equality, about empowerment and social justice."

'261 makes me feel fearless'

But this time Switzer won't be the only woman running — she'll be joined by a team of more than 100 women running for her charity, 261 Fearless.

Although Switzer has been working towards the advancement of women's rights for the best part of 50 years, setting up a charity is an idea she only started percolating on recently.

"About five years ago my bib number, 261, started to become this cult number around the world," she says.

"I was getting these letters from people in Paraguay, people in Japan, people in China, people in Canada, people in Chicago, Australia, and they were all saying the same thing: '261 makes me feel fearless.'

"'It was a very strange feeling because to me that number had simply been just three digits, but what was happening was people everywhere were relating to a story.

"That story of a girl being told she was unwelcome, or wasn't good enough, was too slow, wasn't really an athlete, didn't count.

"Everybody in their lives have been told there's a wrong colour or a wrong religion, or too fat, not pretty enough, not good enough, born on the wrong side of the tracks — and they go and do it anyway when they run and they become real fearless."

Switzer will be joined by a team of more than 100 women running at the Boston Marathon. ( Supplied: 261 Fearless )

Switzer believes the sense of fearlessness and empowerment that comes from running is universal.

"You realise if you can run a kilometre, you can run five and you can run 10 and you can run a marathon, and you can do anything," she says.

So two years ago, with the help of some friends, Switzer drew the surge of interest together into a charity.

"We're really off and running with a series of global clubs and communication tools empowering women," she says.

Switzer hopes her Boston Marathon team of more than 100 women and seven men — "as a tribute to the men who helped me at Boston" — will help put Fearless 261 on the radar so they can start working in harder-to-reach areas.

She describes the charity's work as "training women to train women" — their staff guide women through the process of setting up and managing a running club.

"It's about creating a community of women, of how to break down barriers of judgement and limitations and have everybody meet on an equal playing field," she says.

'You rush forward three steps and fall back two steps'

These clubs are expanding in places like Germany, Austria, the UK, and even China, with locations such as the Middle East, Africa and South America on the horizon for the next few years.

"It's going to be touchy in the Middle East — we don't want to put anybody in a dangerous situation, but there are women in the Middle East who are definitely interested in running and communicating already with us," Switzer says.

Switzer describes the work of 261 Fearless as "training women to train women". ( Supplied: Horst von Bohlen )

Switzer is well aware there's a long way to go when it comes to gender equality — not just in athletics but in the wider world as well.

"You know what's amazing about progress? You get a whole lot done — you rush forward three steps and then you have to fall back two steps and it seems that's the way culture and society moves," she says.

"What we're realising is most of the women in the world still live in a fearful situation.

"You have to look at huge populations where women are second-class and third-class citizens."

Switzer with her husband Roger Robinson in 1986. ( Supplied: Kathrine Switzer )

But Switzer is staunch in her belief — and hope — that running can help women.

"I take great hope in what I have seen running do in Kenya and Ethiopia, in particular, where those women were very downtrodden and really third-class citizens," she says.

"They run, they win some prize money, they go back to their village.

"They don't buy fancy clothes, they build a school or they inoculate the kids or they sanitize the water.

"What's great to see is those women are very, very esteemed — they're not like, 'oh, you're a freak because you run', they're saying, 'wow, I want to be like you'."

It's something Switzer says she has seen in the success of Kenyan runner Tegla Loroupe, who became the first black African woman to win a major marathon in 1994, when she took out the New York Marathon.

Loroupe won the race the following year, as well, by which time she was idolised by many Kenyans.

She has since become an advocate for peace and women's rights, becoming a United Nations Ambassador of Sport in 2006, organising a series of Peace Marathons in Kenya, Uganda and Sudan, and opening a school and orphanage.

Last year, Loroupe was the Chef de Mission of the first Refugee Team to compete at the Olympics.

"The expression 'to run' in Kenya is now 'run like Tegla'. These are heroes that become part of the cultural ethos of a country," Switzer says.

"They're changing the social fabric, and that's how empowerment works, when women change the social fabric."