Why do healthy people get stronger with exercise but people with DMD don't?

DMD, Duchenne Muscular dystrophy.

it's an inherited disorder of progressive muscular weakness.

when you do exercise it it strengthens your mascular strength. but a person with DMD which cannot cannot progress its muscular growth because of muscular weakness. they does not get benefit with exercise.

DMD is nothing but it's the stop of the muscular growth. DMD create an obstacle when you do exercise and tries to improve the strength of your muscles as because the growth has already stopped. there will be no change with exercise.