They have lots of injuries due to the strain on the body due to hard training.

Not only in US. About 50 % of Swedish and Norwegian cross-country skiers suffer from asthma symptoms.

Of course, as others have pointed out, there may be misuse/abuse as well.

"suffer from asthma symptoms"

This was a way to get clenbuterol for a long time. And still is. The "illness" is over-indexed by a large margin.

Right, another example is ADHD diagnosis for American Football players. It's used to hide steroid use.

http://profootballtalk.nbcsports.com/2012/07/31/is-adderall-...

Kind of. The NFL does not release the drugs that players are testing positive for. Test positive for Adderall and it's the same as testing positive for Winstrol. Players are incentivized to take Winstrol (or other AAS), and if they test positive, they just come out and say it was Adderall without a use exception (TUE).

Since the NFL won't publicly rebut their arguments, NFL players are free to lie and make up ADHD diagnoses.

Apologies if you were saying this, but some people (including commenters to that article) are confused.

Yep that what I was trying to say

How comes that it's fine for some athletes to be genetically favoured- maybe because they put up muscle mass more easily, or because their blood has a higher concentration of red cells, and it's not allowed for others to use drugs to get to that same level; however athletes that have lower resistance to muscular or bone strain are allowed to get on par with the others through the continuated use of drugs?

On the other hand, people who are genetically too favoured may be banned from the sport - though they used no illegal performance-enhancing substances at all.

At least FIS has determined a hemoglobin limit for skiers, and UCI a hematocrit cap for cyclists. If your natural hemoglobin or red blood cell percentage is higher than the limit: tough, you can't participate.

Norwegian cross-country skier Sundby was using abnormal dosages of asthma medicine. The same method is used in cycling. You be the judge what's the reason for that sort of behavior.