Deltoid (Made up of 3 heads: anterior, lateral, and posterior)
Muscle: Anterior Deltoid Origin: At the lateral third of the clavicle (collar bone), on the anterior border.
Insertion: At the deltoid tubercle of the lateral surface of the humerus
Function: Humeral flexion; works with the pectoralis major in drawing the arm forward. It is a strong abductor of the arm. The anterior deltoid’s lower fibers weakly adduct and rotate the arm inward.
Muscle: Lateral Deltoid Origin: At the acromion process on the scapula.
Insertion: At the deltoid tubercle on the lateral surface of the humerus
Function: Abduction of the humerus. It is aided by the supraspinatus, and the upper fibers of the anterior and posterior deltoid in abduction. It is limited by the tightening of the lower shoulder capsule. The lateral deltoid contracts to abduct the humerus, while the anterior and posterior deltoid stretch to steady the humerus.
Muscle: Posterior Deltoid Origin: At the lateral aspect at the inferior edge (below the top, outside edge of the shoulder blade) of the spine of the scapula
Insertion: At the deltoid tubercle of the humerus
Function: Humeral extension. It assists the latissimus dorsi and teres major in drawing the arm backward into extension. The lower fibers weakly adduct and outwardly rotate the arm.
Indication of Weakness: Anterior Deltoid: Overhead presses become difficult and painful. Acromioclavicular (AC) joint sprain will cause weakness, since the anterior and lateral deltoid cannot contract properly in an unstable joint.
Shortening of the infraspinatus and pectoralis major will decrease ROM in arm abduction. Fixation of the scapula to the thoracic wall can also decrease ROM in arm abduction. The posterior deltoid is weakened when the anterior deltoid and pectorals become shortened and hypertonic, causing agonist-antagonist muscle inhibition.
If the glenohumeral joint has shifted forward due to shortened muscles, it needs to be treated or stretched to allow the posterior deltoid to contract properly again.
Optimal Training Principles: The shoulder joint has the largest range-of-motion (ROM) of all the bodies joints. This ROM is brought about because the shoulder joint relies on muscles and ligaments for stability, instead of the skeletal structure. Unfortunately, this great ROM makes the shoulder more susceptible to injury than other joints.
In order to keep the shoulder capsule healthy and maintain optimum performance, will require you to train all the muscles of the shoulder and rotator cuff for both strength and flexibility. The anterior deltoid is often over-trained. All chest and shoulder exercises will recruit the anterior deltoid.
Bodybuilder’s target the anterior deltoid with dumbbell front raises. These exercises are not necessary since side lateral raises, chest presses (particularly the incline chest press), chest flyes and all shoulder exercises, target the anterior deltoid. The lateral deltoid is stressed in barbell, dumbbell and machine shoulder presses and dumbbell side lateral raises.
To maximize stress on the lateral deltoid during shoulder presses, keep the elbows flared at 9 o’clock and 3 o’clock (elbows directly out to the side). While this position is ideal for stressing the lateral deltoid, some athletes may find it painful and difficult, if not impossible to get their elbows in this position.
If this is the case, elbows positioned at 4 o’clock and 8 o’clock (elbows slightly in front of the body) or 5 o’clock and 7 o’clock will make the exercise more comfortable by taking the stress off of the shoulder capsule. The more the elbows move anterior to the shoulder, the less stress on the lateral head. The same is true regardless of whether the athlete uses barbells, dumbbells or machines.
The difference is in the stability of the shoulder press. Machines afford the greatest stability, which is preferable for beginners. Advanced athletes are going to need dumbbells in order to make the exercises less stable and therefore place more stress on the shoulder’s stabilizer muscles.
Important Safety Notes: Keep the wrists straight, thumbs wrapped around the bar and elbows directly under the wrist while performing shoulder presses. Behind-the-neck presses are considered a “contra-indicated” exercise (high risk of injury-with limited or no additional benefit, not recommended for most populations).
The behind-the neck variation places maximal stress on the cervical disks and muscles attached to the cervical disks and increases the risk of cervical disk herniation and rupture. It also places maximal stress on the shoulder capsule.
The side lateral raise is an excellent isolation exercise for the lateral deltoid. This can be performed on machines or with dumbbells (dumbbells will work the important stabilizer muscles surrounding the shoulder capsule).
Dumbbell side raise with the hands at 3 o’clock and 9 o’clock places maximal stress on the lateral deltoid, but just like the shoulder press, some athletes may find this position uncomfortable or painful. The 4 o’clock – 8 o’clock or 5 o’clock – 7 o’clock positions will reduce both the stress on the shoulder capsule (increasing safety and comfort) and the lateral deltoid (decreasing effectiveness).
Important Safety Notes: It is recommended for both safety and comfort that the elbows remain slightly bent (10-15 degrees) through-out the exercise, you do not raise the elbow above shoulder level and you avoid the “pouring tea variation” (bodybuilders like to rotate the hand at the top of the movement by rotating the little finger up and thumb down -simulating pouring tea).
These 3 violations of safety guidelines cause shoulder impingement and elbow stress. One thing you may want to consider for your athletes is to have them perform their side raises with their knees bent (5-15 degrees) and angled slightly forward from the waist (5-15 degrees) while maintaining weight-lifters arch and good posture (scapula retraction).
The lateral deltoid in many athletes is more posterior than directly lateral and this position will enable them to more directly stress the lateral head. Bent-Over-Lateral-Raises target the posterior deltoid.
It is recommended that you use a “high-bench” or sit at the end of a bench with the dumbbells moving under the thighs. Many athletes will find bent-over-lateral-raises stressful on the lower back. If no bench is available, have the athletes bend their knees (10-30 degrees) depending on comfort and flexibility), maintain good weight-lifters arch and scapula retraction.
Maximize stress on the posterior deltoid by keeping the back parallel to the floor (bend knees for comfort), maintaining the hands in line with the shoulders and contracting the posterior deltoid until the arms are parallel to the floor.
Good chest and shoulder flexibility will be needed to keep hands in line with shoulders and contract through full ROM. The exercise becomes less effective if the hands move behind the shoulders, you lock your elbows or you raise your torso above parallel to the floor.
Important Safety Notes: Losing the weight-lifters arch and/or knee bend stresses the low back and hip joints. Locking the elbows stress the elbow joints. Performing the “pouring tea variation” stresses the shoulder joint.
Dr. Jim Bell