But in general, the average exerciser can expect to gain anywhere from a half pound to 2 pounds of muscle in a month of training, according to the American Council on Exercise.

Experts say 30-45 minutes, 3-5 days a week, plus daily movement, helps rebuild muscle after 50. See how to structure your plan.

Looking to put on muscle at the gym, but don't know where to start? Check out our tips for creating a six-month plan, including diet, workouts, and how to stay motivated.