The Tour de France might be cycling's biggest and hardest event, but since 1989 only men have been eligible to take part in the official multi-stage race. 

That's why this year women from around the world are racing each stage a day before the men to highlight the inequality in cycling's top prize.

The event is called Project Donnons des Elles au vélo J-1(or Project Give the girls a bike in English) and started with three French women riding the Tour ahead of the men in 2015. Now in its fifth year, 13 French cyclists are taking on the twists and turns of the Tour and for the first time, another team of ten are joining – called the InternationElles – hailing from further afield including the UK, America and Australia.  

The InternationElles have taken time off from their day jobs – the team includes a lawyer, a psychologist and a scientist – to complete the 21-stage race that covers over 3400 km from Belgium to Paris.

This year is the 106th edition of the Tour de France, but the history of the race for women has had as many ups and downs as the course itself. A women's edition – Le Tour de France féminine –was launched in 1984, with the cyclists completing 18 of the 21 stages starting a few hours ahead of the men each day. After the initial and short-lived success, the race has gone through many different iterations and changes until it disappeared from the calendar entirely in 2009.  

Both teams are racing to expose this disparity. On their website, the InternationElles described their aim to "raise awareness for gender equality in cycling and to campaign for women's tours to be held alongside the men's".

The cyclists started their challenge on July 5 and should complete the Tour on July 27. Both the InternationElles and the Donnons des Elles au vélo team are documenting their progress on Instagram as they continue to ride for equality.