The subscapularis muscle can be isolated and tested by having the patient push their elbow outward against resistance while their hands are on their abdomen.

“put your hands on your abdomen this way push your elbow out against me that is all subscap that is all subscap”

“if you have a complete subscap off this elbow will when you do that maneuver will fall back it'll just fall away you literally can't maintain that position”

“now we isolate the superspinatus that that that elevator of the shoulder that's so important and so here we push straight up hard and your rock solid and that isolates the supinatus”

“put your hands on your abdomen this way push your elbow out against me and that is all subscap that is all subscaps”

“if you have a complete subscap off this elbow will when you do that maneuver will fall by it'll just fall away you literally can't maintain that position”