When the country went into Covid lockdown, gyms and workout studios were forced shut.

Many Australians turned to running to keep fit, and became addicted to the high.

The popularity is clear, with the Sydney Marathon drawing 33,000 entrants this year, up from just 3000 people in 2022.

For many, it started with the park run, then a 10-kilometre event. Soon, it’s a half marathon, a full marathon, and suddenly – ultramarathons seem possible.

Now health professionals are warning runners that there is another side to the sport that they should be aware of.

Bone-stress injuries, which is a reaction in the bone from repeated overloading, are on the rise. At first, it may be hard to detect, and masquerades as tightness. But if left untreated, the pain can turn severe and result in stress fractures.