The Supine Manual Resistance ER(External Rotation) at 90-degrees and in the scapular plane is a beginner exercise we use here at BPT for shoulder strength and stability. This exercise focuses on the posterior area of the shoulder and upper back where our rotator cuff muscles reside. These muscles are largely used in the deceleration of the arm during throwing and other overhead movements, so they must be extremely strong and resilient to be able to counteract such a dynamic movement.
This exercise will be performed with a partner, one arm at a time. To begin, lie in a supine position (on your back) on a table and have your partner support the elbow of one arm directly off the shoulder. This arm may be propped up slightly for comfort using a half roller or towel. The partner will also place support and slight resistance on the wrist of that arm while the arm is laid back creating a 90-degree angle at the elbow. The person lying on their back will externally rotate the shoulder while their partner supports the elbow and provides resistance on the wrist. The amount of resistance will depend on the strength of the person performing the external rotation. Repeat the same process in the scapular plane, with the elbow slightly above shoulder height.
Because we classify this exercise as "beginner" does not mean we do not use it with intermediate and advanced athletes. It is a fantastic arm car exercise for everyone! The exercise can be performed for reps(8-12), time(20-30 second hold), or a little bit of both(8 reps with a 3-second hold every rep).