Following Simone Biles' decision to withdraw from two further events in Tokyo, BAC Chair, Vicki Aggar, explains the significance of the American gymnast's actions in the wider context of mental health within sport.For the many exceptional performances and COVID-related irregularities of the Tokyo Games, there is every chance that the most defining moment of this Olympics will be a young woman deciding that she wasn’t in the right headspace to compete.The phrase ‘defining moment’ – in a sporting context – usually refers to performances which will be remembered for years or even decades, and inspire generations to come. What Simone Biles choose to do at Tokyo’s Ariake Gymnastics Centre this week ticks those boxes and more.For a long time sport, like society, has not treated mental health with the respect and importance that it deserves. Whilst there has been ample focus and investment on getting athletes back to health after a physical injury, for decades, mental wellbeing has been at best misunderstood, and at worst, ignored.There’s no doubt now, that things are changing.While some of the more general reaction to Simone Biles’ withdrawal illustrates the progress still to be made in society’s understanding of mental health issues, it was incredibly heartening to see the universal support that her decision attracted from her fellow athletes.These athletes – for the most part, of Simone’s generation – have grown up surrounded by a more progressive attitude to mental health, and are involved in an elite sport system which, while still being some way short of perfect, has genuinely now begun to invest in its athletes as people, rather than sporting commodities.Like us at the British Athletes Commission, many of Biles’ peers see this as a potentially seminal moment in sport. For one of the highest-profile names at an Olympic Games to, whilst in the running for a fifth career gold medal, put her mental health first is a huge statement.Her courage can now ensure that the conversation can move on even further; that athletes can feel more comfortable speaking out about such issues; that decision-makers within sport will find it impossible not to factor in mental health considerations when building an environment for training or competition.For all Simone Biles’ countless extraordinary achievements, pushing forward the conversation on mental health and providing a courageous and unprecedented example to current and future athletes around the world, may just turn out to be her most important.The BAC represents over 1,200 of Great Britain’s elite athletes, and can provide confidential and independent mental health support. This support can be accessed via support@britisheliteathletes.org.