When Olympic gold medallist Dani Rowe retired from elite cycling, the self-confessed exercise addict set her sights on the 2019 London marathon.
The 28-year-old had competed for Wales in last year's Commonwealth Games and was in peak condition - she thought.
But within months of starting running she developed two stress fractures in her right leg, and a scan showed the start of another in her left.
"I wanted to get straight into running… I never thought my bones wouldn't be up to it," the three-time world champion said.
Experts said all the hours of bike training meant her bones were not used to any impact, even though her bone density, which had been monitored during her cycling career, was normal.
Why does this not surprise me? Cycling is certainly not impact sport.