The One Arm Standing Cable Chest Press.
We see a lot of people doing a version of this exercise, before they are ready. Not to say they are doing it incorrectly, but there are a couple ways execute it. Until you strengthen the periscapular muscles and properly stabilize your shoulder blade while going through the motion, you shouldn’t over rotate your torso or abduct (separate) your shoulder blade. Let’s take a look:
Notice the tight, packed shoulder throughout the entire range of the pressing motion. Regardless of the position of the arm, the shoulder blade stays tight to your back and shoulder is ‘sucked’ into the socket. This is a position where your pectoralis, anterior deltoid, and triceps are still the movers, but your posterior muscles (Rhomboid, Rotator Cuff muscles) are engaged and active in stabilizing your shoulder blade and shoulder joint. The rotation of the upper arm gets those rotator cuff muscles to work in the movement as well. Getting away from the shoulder and to the core, all of your ‘abs’ (rectus, transverse, and obliques) are involved in keeping your torso still against the force of the weight in the cable. Remember, abdominals aren’t just for moving you through your torso, they stop movement as well.
Once control over your shoulder blade is maintained and mastered, then the ‘press plus’ is perfectly acceptable. So for those of you with strong, healthy shoulders that are capable of stabilizing, lets take a look:
There is still loading of your posterior muscles at the beginning of the movement, and tension in them throughout. This will allow you to keep an injury safe shoulder joint while getting a greater range of motion and some new muscles involved. The same muscles give you the pressing motion, but the Pectoralis Minor is now involved moving your shoulder joint forward. The Obliques are now rotating your torso on the forward motion, as well as resisting coming back, and then stabilizing at the pause before you start forward again.
This motion will imitate any single arm pushing movement in real life, regardless which of the two versions you choose. As always, start with a lighter weight and master the movement. After you are confident in every aspect of your form, increase the weight to something that is challenging, but still allows you to use perfect form.