You'll do both of the exercises unilaterally with a cable handle attached at shoulder level.
One-Arm Cable Pec Flye Drop Set
- Do a set with your torso perpendicular to the cable so the cable is just outside the shoulder of your working arm. Do 8-15 reps.
- Once you've done both arms, go back to the arm you started with and do a set while facing away from the column so the cable is directly behind your hand when your arm is out to the side.
The point of max mechanical tension is when your arm is at a 90-degree angle to the cable. So when doing the exercise with your torso perpendicular to the cable, the movement of horizontal shoulder adduction is challenged far more when your arm is in front of and across your torso (in the mid to shortened range).
On the flipside, facing away from the cable column challenges this same movement far more when your arm is out to the side (in the lengthened to mid-range).