Hmm. Sounds like a you are writing a novel. This is not my area.
But McArdle's disease is characterized by an extreme intolerance of running. The body cannot break down glycogen in muscles because of an inherited recessive gene. McArdles Syndome sufferers are usually very sedentary.
Kearns-Sayre syndrome is also a genetic disease. It manifests with all kinds of symptoms, usually with extremely poor depth perception and hand-eye coordination, such that catching a ball is impossible. Running results in bad falls. This is due to abnormal eye muscle control. These folks would never pass a drivers license exam in most places.
This would be a decent guess - I assume you want a malady that when managed is not fatal, but is persistent.