Olympic cycling star Laura Trott has changed her mind on whether wearing cycle helmets should be a legal requirement. While she still thinks helmets prevent major injuries, the 21-year-old now thinks helmet use should be a matter of "personal discretion".

Speaking at the Olympic Velodrome at Lee Valley Velopark last week, Trott reiterated that her sister’s crash had convinced her of the benefits of helmets.

"I cycle a lot around roads and I would always wear a helmet," she told Rob Virtue of wharf.co.uk. "I've been out with my sister when she crashed and it just showed me how a helmet prevents major injuries.”

Emma Trott, who is two years older than her sister, was one of five British riders hit by a car in Belgium in 2010

But in a change from her previous comments Laura Trott added: "But it's also something that should be at your personal discretion. If you want to wear it, wear it, if you don't, then don't."

Last year, the Wiggle-Honda rider attracted vociferous criticism when she implied that cyclists sometimes have only themselves to blame should they get hit by a vehicle. “It’s not always the car’s fault,” she said.

At the time, Trott was speaking in her role as one of Mayor of London Boris Johnson’s cycling ambassadors.

“It should be a legal requirement to wear a helmet,” she said. “So many lives have been saved by them and it saved my sister’s life.”

However, Boris Johnson’s own cycling commissioner Andrew Gilligan believes helmets have no proven benefits and refuses to wear one.

The benefits of helmet use is one of the most hotly contested topics in cycling. British Cycling policy advisor Chris Boardman recently called for the debate to be put to bed as it had become a distraction from the bigger issues of making cycling safer by building segregated infrastructure and improving vehicle design.

In an interview with road.cc, Boardman said that helmet use was “not even in the top 10 of things you need to do to keep cycling safe or more widely, save the most lives.”

Studies based on A&E admissions often conclude that helmets are effective at preventing head injury. But this effect vanishes when data from larger groups of cyclists are examined.

In 2005, researcher PJ Hewson analysed police STATS19 data on traffic collisions and concluded: “There is no evidence that cycle helmets reduce the overall cyclist injury burden at the population level in the UK when data on road casualties is examined.”

In a 2006 paper for the British Medical Journal, researcher Dorre Robinson, also working with whole-population data for injury rates concluded that there was no clear evidence of the effectiveness of making helmets compulsory.