Probably should add, since exercise is good for preventing atrophy... I do not wear any braces when I exercise. Do you currently wear your foot drop brace all the time? I wear them when out and about, working, shopping, etc.
Are your motor nerves to certain muscles damaged from the pn? Mine are, that is why the braces are so beneficial for me. While it is good to stimulate the nerves to help with atrophy, which I do through exercise, it is hard to push through an entire day with damaged motor nerves. That was where the braces came in, they make it able for me to work, and carry on a normal life, where as without them my body was too fatigued.
Hopefully all this info will help you with your decision-----I hope you find some relief either way. You always have the option of both, exercise and braces. You do not need to wear them all the time.