While the scapulae require some degree of mobility to perform the various movements of the arm, they fundamentally need to remain stable to promote normal mobility within the shoulder joint. During these movements, insufficient, premature,
or excessive activation of specific scapular muscles (e.g., dominant rhomboids resisting upward scapular rotation, overactive upper trapezius forcing excessive scapular elevation) will compromise scapular stability, which
in turn affects the ability of the muscles around the glenohumeral joint to execute their function effectively. For example, if the scapulae cannot sink slightly while the arms extend overhead, this may interfere with scapular rotation and scapular stability. This forces the shoulder joint to assume greater loads, reducing its force-generating capacity and increasing the potential for injury. This illustrates the importance of setting or packing
the scapulae prior to shoulder flexion or abduction movements.
To kinesthetically improve awareness of good scapular position, improving flexibility and strength of key parascapular muscles, try the following sequence of movements:
• Lie on your back on a mat with knees bent to 90 degrees and the feet placed flat on the floor, aligning the hips with the knee and second toe.
• Position the arms at the sides of the trunk with the palms facing upward.
• Engage the core muscles to stabilize the lumbar spine in the neutral position. Maintain this position throughout the exercise.
• Perform two to four repetitions of each of the following, holding each contraction for five to 10 seconds:
- Scapular depression (sliding the shoulder blades downward)
- Scapular retraction (squeezing the shoulder blades toward each other)
Once you have mastered packing the scapulae while lying on your back, perform the same movement sequence while seated. Use the tactile experience gained from doing this in the lying position to guide your action in the seated position. Once you have mastered both the lying and seated versions of shoulder packing, start to perform light-weight pushing and pulling exercises (e.g., chest presses and rows with an elastic resistance tube, respectively) from the packed position, getting a feel for how the muscles that support the scapulae stabilize the shoulder and hold it in place during movement. Finally, begin to perform movements with the scapulae unpacked, but still stabilized with the same muscles used for packing, and progressively increase the loads.
It is important to learn the action of scapular packing so that you can become aware of the muscles involved in supporting and stabilizing the shoulder joint. However, when it comes to lifting most loads and performing activities of daily living, you want to allow your scapulae and shoulders to move in a natural rhythm while those muscles are actively supporting the shoulders. One exception is performing a very heavy bench press, like the one used to compete in a weightlifting event or find your 1 repetition maximum, when maintaining a packed scapula is a good idea.