Strengthening the scapular muscles is essential for improving and maintaining scapulohumeral rhythm -- the coordinated movements between the humerus bone of your upper arm and the scapula bone, which includes the shoulder socket in which the head of the humerus fits. A physical therapist may recommend performing isometric-strengthening exercises if your scapulohumeral rhythm breaks down due to an injury. Isometric exercises are stretches during which the muscle contracts without changing length and your joint doesn't move. These exercises are also beneficial if you have poor posture.
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Isometric Scapular Protraction
The pectoralis minor and serratus anterior muscles contract to pull the outer edges of the scapula bones in your upper back forward -- called scapular protraction. To strengthen these muscles isometrically, stand upright with your arms hanging at your sides, turn your palms to face outward and move your shoulders forward and inward, like you're trying to pinch them together in front of your chest. Hold this position for at least five seconds, then relax and return your arms to your sides. Repeat the exercise multiple times.
Isometric Scapular Retraction
Scapular retraction involves moving the scapula bones backward and inward, like you are trying to squeeze an object between them. The rhomboids and trapezius muscles in your upper back help facilitate this movement. Perform the isometric scapular retraction exercise to strengthen these muscles. Tie the middle of a resistance band to a doorknob and hold the ends. Back away from the door until the band is taut, then extend your arms in front of your chest with your palms facing downward. Flex your elbows and pull them behind your back as far as possible, squeezing your shoulder blades together. Hold this position for five seconds or more.
Shoulder packing is another isometric exercise that works the rhomboids and trapezius muscles. Sit or stand with your arms at your sides, chest forward and chin up. Contract your abdominal muscles to stabilize your spine, then squeeze your shoulder blades together for five to 10 seconds, moving your arms behind your body. Complete two to four repetitions. You can also perform the exercise one side at a time, pinching your left shoulder blade inward for five to 10 seconds, followed by your right.
Shoulder shrugs work the levator scapulae muscles on either side of your neck and the upper fibers of the trapezius muscles, which coordinate to elevate the scapula bones. Start in the same position as you did for the shoulder packing exercise, but lift your shoulders upward rather than pulling them backward. Move them as close to your ears as possible and hold for at least five seconds. Hold a barbell across the front of your thighs or dumbbells at your sides to increase the resistance and make the exercise more challenging.
Consult with a professional to learn the most appropriate exercises for your situation. Work with a personal trainer to learn how to do isometric exercises correctly.