Viktor Thorn, Hanna Falk, Charlotte Kalla, Jens Burman.

These are some of the national team skiers who have suffered from long-term back problems in recent years.

- I could list about ten people who have serious back problems.

Now it feels like half the national team has back problems, says Viktor Thorn.

The 24-year-old has had recurring back problems.

Disc herniation has made up for it, just like for Burman and Falk.

- I felt that I was approaching the top three years ago.

Then there were problems with the back and surgery after surgery.

Genetics

SVT Sport has previously reported that Hanna Falk is considering ending her career after the season.

Thorn and Falk both agree that they may have a genetic predisposition to get herniated discs.

- I think it's about it being genetic and that you have been unlucky.

And maybe I trained for many hours when I was weak in the body, says Thorn.

Falcon:

- We run very many hours, we stake very many hours.

Monotonous movements and shocks and a little compression all the time.

If you have some genetics to get back problems, you may go for it at the age of 25-30 instead of at the age of 60.

Elite sports are not always healthy, she says.

Cross-country skiing more explosive

Other reasons may be the fact that cross-country skiing has become more explosive.

The ability to change pace is absolutely crucial not only in sprint but also in mass start.

The more power the rider creates, the more strain there will be on the back.

Hanna Falk can not put her finger on any adjustment she made in her approach that caused the back problems.

- The back is an exposed part for us cross-country skiers, much like the knees are exposed for alpine skiers.

For my own part, I have not changed the training radically and then I got back problems.

For me, I think it has been long abrasive and a lot of strain over a long time as it is in cross-country skiing.

Maybe that's why an investigation by the union is needed.

Neither Thorn nor Falk can speak for what other skiers have done or not done.

- I can only speak for myself, says Thorn.

- We have all filled in an exercise book over the years and they know roughly how we have trained.

Then maybe they can see a common thread how it is with everyone who has problems now.

Thorn hopes an investigation by the ski association can provide answers to the riddle.