To persuade a stubborn pair of pecs to grow, you’ll need to put some more pressure on them. This means increasing their time under tension (TUT)—the duration your muscles are contracting during a given set or workout.
Yes, you could just accomplish this by increasing the total number of sets. But you can also achieve greater TUT by performing isometric contractions—that is, tensing the muscle without moving it—on every set of bench presses and cable flyes.
Try these four techniques to ratchet up the tension and see major gains.