Standing Cable Flies
Standing cable flies is a good exercise to target the middle of the chest, stretching the chest fibers connecting to the sternum. It therefore helps to pull the sternum out and as a result is an excellent exercise for those with Pectus Excavatum.
Grasp two opposing high pulley dumbbell attachments. Stand with pulleys to each side. Bend over slightly by flexing hips and knees. Bend elbows slightly and internally rotate shoulders so elbows are back initially.
Bring cable attachments together in hugging motion with elbows in fixed position. Keep shoulders internally rotated so elbows are pointed upward at top and out to sides at bottom. Return to starting position until chest muscles are stretched. Repeat.
Under greater resistance, positioning torso at lower angle downward (by bending over at hips), will allow upper body weight to counterbalance upward pull of cables, as opposed to stepping forward and struggling with the backward pull of cables.
Pectoralis Major, Sternal
Pectoralis Major, Clavicular