Well-shaped shoulders are not always that easy to develop, and shoulder training is complicated because shoulders can be vulnerable to injury. However, most shoulder injuries arise from poor exercise form in shoulder, chest or back exercises. Nevertheless, the risk for obtaining shoulder injuries can be minimized by paying careful attention to exercise form. Seated dumbbell raises will activate the deltoid muscle1 of the shoulder while minimizing injury risks, and a few months of effort will reshape and firm the entire muscle.
Overview of the Deltoid Muscle
Although they are not truly separate heads, the deltoid muscle does originate from three regions on the bony portions of the shoulder, and each region differs in function. The anterior fibers of the deltoid begin on the lateral part of the clavicle (collar bone).2 These fibers flex the humerus bone at the shoulder (bringing the humerus bone forward), and also medially (internal) rotates the humerus bone at the shoulder.2 The posterior fibers of the deltoid are activated to some degree in seated dumbbell raises, if they are done with the body slightly bent forward. The fibers in the posterior part of the deltoid begin on the upper and posterior side (spine) of the scapula.2 The posterior fibers of the deltoid extend the arm by pulling the humerus bone of the upper arm posteriorly. The medial fibers of the deltoid are most strongly activated by seated dumbbell lateral raises.3 The medial fibers of the deltoid are attached between the starting positions of the anterior and posterior deltoid fibers with attachments along the acromion of the scapula.2 The fibers from this muscle converge to anchor to the anterior (front) and upper portion of the humerus bone of the upper arm.2 The medial fibers primarily produce abduction of the humerus (raising the humerus away from the side of the body). This is the primary activator of dumbbell lateral raises.3
Although the seated dumbbell raise is a deltoid exercise, it also activates part of the delicate rotator cuff musculature. The supraspinatus muscle of the rotator cuff begins near the medial side of the scapula bone and runs over to the superior part of the head of the humerus bone of the arm.2 The deltoid muscle covers the tendon of the supraspinatus muscle. Along with the lateral fibers of the deltoid, the supraspinatus acts to abduct the humerus. The supraspinatus muscle is most active between positions where the arm is nearing a position that is parallel to the floor4 in the dumbbell lateral raise. The other important function of the supraspinatus is to hold the head of the humerus into the glenoid cavity (shoulder socket) of the scapula. It is really the only muscle of the rotator cuff that does not have a rotational function.2
Seated Dumbbell Lateral Raise
This exercise activates the medial deltoid and supraspinatus strongly and the posterior deltoid is moderately activated as a result of leaning slightly forward.5 If one bends over excessively, it will convert to a posterior deltoid exercise, so selecting the correct starting position is important.
1. Select a set of light dumbbells and sit at the end of a flat bench with your feet firmly on the floor. Hold the dumbbells so that your palms face each other and your arms hang straight down towards the floor. Bend over just slightly (about 5 degrees). This will be your starting position.
2. Keep your torso stationary. Bend your elbows just slightly and begin to lift the dumbbells upwards (shoulder abduction).
3. Continue to lift the dumbbells upwards, but as you raise the weights, turn the hands slightly so that the little finger side of the hand is tilted upwards towards the ceiling as if you were pouring water in a glass.
4. Raise the dumbbells until your upper arms are parallel to the floor. There is no need to lift higher than this, otherwise the upper fibers of the trapezius, upper back muscle, and rotator cuff muscles will be doing the work, rather than your deltoid muscles.
5. Slowly control the descent of the dumbbells towards the floor. Do not pause at the bottom, but immediately begin the lift upward. This will keep the deltoid fibers firing throughout the set. After you have completed 12-15 full repetitions, you can rest 60 to 90 seconds before starting your next set. Start with two sets and then you can add a third set after a couple of weeks of training.
The shoulder joint is vulnerable to injury if the exercise is done quickly, or if the weight is jerked upward in a quick fashion. It is more important to isolate the muscle regions of the shoulder and work in slow, smooth movements and with relatively strict movements. If you are careful in your exercise form and diligent in your training over the next few months, you will be surprised at how effective this exercise can be.
Your shoulders and particularly the medial part of the deltoid will be activated by the seated lateral raise6 and take on a whole new firmness that you will want to show off!
- Parry JS, Straub R, Cipriani DJ: Shoulder- and back-muscle activation during shoulder abduction and flexion using a Bodyblade Pro versus dumbbells. J Sport Rehabil 2012;21:266-272.
- Moore, KL and AF Dalley. Clinically oriented Anatomy. Fourth edition. Baltimore, Lippincott Williams & Williams. 1999; pp. 690-698.
- Jakobsen MD, Sundstrup E, Andersen CH et al: Evaluation of muscle activity during a standardized shoulder resistance training bout in novice individuals. J Strength Cond Res 2012;26:2515-2522.
- Reed D, Halaki M, Ginn K: The rotator cuff muscles are activated at low levels during shoulder adduction: an experimental study. J Physiother 2010;56:259-264.
- Reinold MM, Macrina LC, Wilk KE et al: Electromyographic analysis of the supraspinatus and deltoid muscles during 3 common rehabilitation exercises. J Athl Train 2007;42:464-469.
- Youdas JW, Arend DB, Exstrom JM et al: Comparison of muscle activation levels during arm abduction in the plane of the scapula vs. proprioceptive neuromuscular facilitation upper extremity patterns. J Strength Cond Res 2012;26:1058-1065.