What disease occurs when the person does a lot of physical strength?

My question is: I would like to know what illness or problem it gives in a person who does a lot of physical strength. To be clearer, I know a person who says he has a problem, said he was not going to tell me what it was because it was kind of ugly, and he could only tell me that it was a result of having done a lot of work. Said also can not walk longer distances, ride a motorcycle. Thank you in advance for your attention!
Expert answer:

I have an idea of ​​what your friend might be talking about, but I'm not going to tell you, and it's not that bad, it's funnier than serious, and you can stay calm, it's not contagious. As he did not want to tell you, it is better to respect his desire, with time and with confidence in you he will tell you, but at first it leaves there.