Once you get beyond the beginner stage of weight training—when you can do just about anything and see progress—you need to learn to “periodize” your workouts. Periodization is a general term for any plan that allows you to make long-term gains while avoiding plateaus and injury, but the concept itself doesn’t have to be as complicated as its name.
“You can add weight to your exercises,” says Jason Ferruggia, a strength coach and author in Los Angeles. “Basically, change the exercises, do more reps, sets, or rest less between sets.” Change everything, in turn, over time, and then change again as needed.
Of course, there are more sophisticated and organized systems of periodization out there aimed at strength, muscle size, and sports performance, but one approach isn’t necessarily better than another, provided it’s well thought out and goal-oriented.
Try gathering a bunch of trainers together, though, and most of them will argue till their protein shakes turn sour that one system trumps all others. Fortunately, research is showing otherwise.