Workouts like barre, Pilates, as well as long runs all have their place and benefits, but if it's muscle you're after, weightlifting is your best bet. Instead of randomly selecting exercises with sets and reps schemes that don't make sense, you've got to design a proper workout plan.
Before you pick up a weight make sure your program focuses on muscle hypertrophy (maximal muscle growth), doing three to five sets of 12 to 15 reps per exercise, Rondel said. You'll also want to lift heavy (here's a guide to determining your weights) and incorporate compound exercises — multijoint movements that work large groups of muscle — into your workouts. On the days that you lift heavier, you should do eight or fewer reps, lifting a minimum of 80 percent of your one-rep max to help your muscles grow.
Don't forget to do your recovery work after training, and make sure you getting enough rest each night to help improve recovery and muscle growth.