The parents of a six-year-old boy who ran a marathon in nearly nine hours revealed on Monday they have been visited by Child Protective Services - as they slammed athletes for sparking their children's 'emotional breakdowns.'

Ben and Kami Crawford, of Bellevue, Kentucky, have been heavily criticized online since they first posted photos of their son, Rainier, running in the 26.2-mile Flying Pig Marathon in Cincinnati, Ohio on May 1.

And in an Instagram post on Monday, they shared a photo of Rainier, shirtless, as he was interviewed by a Child Protective Services social workers, writing: 'On Friday, social workers came to our house and interviewed our children because leaders in the running community call running with children wrong.'

'This needs to stop,' they captioned the post.

'Our children are having emotional breakdowns, NOT from running, but from a mob that has been weaponized by running's most accomplished and celebrated individuals,' the Kentucky parents wrote, in an apparent jab at US Olympian Kara Goucher who previously tweeted that six-years-old is too young for a marathon.

'They are stating that children running is abusive and not providing any data or facts,' the parents of six continued in their Facebook post. 'The reports and stance are false.