A-Train (Jessie T. Usher) may be the fastest man on Earth (for now), but he has an unhealthy obsession with his own image. Constantly worried about losing his title, and thus his place in The Seven, he develops an addiction to Compound V, which he uses to enhance his performance. This leads to heart problems, necessitating an eventual transplant, and brings up some frustrating points about his powers.
For one, why is A-Train the only hero whose powers seem to decline with age? We see Maeve and Starlight training to keep their strength up, but Homelander and Soldier Boy seem as powerful as ever, and they don’t ever set foot in a gym. Additionally, why is A-Train’s ability the only one that seems to negatively affect his health? We know he can heal quickly, given how quickly he recovers from a broken femur. Even if he had some help from Compound V, if he can rapidly mend his bones, why not his heart? Plus, given that his body must be extremely durable to survive moving faster than the speed of sound, why is his heart this weak? Finally, if anything, wouldn’t more Compound V strengthen his heart as well as his legs?
Source From: www.slashfilm.com