The deltoids, which make up the musculature of the shoulders, are among the most important muscle groups in terms of the performance of both sport-related movements and activities of daily living. Whether your goal is to spike a volleyball or place items on an overhead shelf, or anything in between, strong shoulders are vital.

The shoulder is a complex ball-and-socket joint capable of flexion, extension, rotation and more, which is what makes training the deltoids so complex. Anatomically, the deltoid is one large triangular muscle divided into three parts (or heads) based on the attachment of the muscle's fibers—the anterior, medial (or middle) and posterior deltoid (Figure). Many exercisers focus on the part of the shoulder they can see in the mirror while training (i.e., the anterior deltoid) and neglect the medial and posterior portions. Unfortunately, the resulting imbalance can sometimes lead to injury and dysfunction.

What the Research Reveals

To determine which exercises best activate the shoulder muscles, ACE-sponsored research evaluated 10 exercises popular among both athletes and the typical gym-goer. The researchers began by evaluating each of the study’s 16 participants’ one-repetition maximum (1-RM) on seven of the 10 following exercises:

*1-RM was not collected for these exercises, which use body weight or the rope as resistance.

On two subsequent workout sessions, researchers placed electromyograph (EMG) electrodes on the three different heads of the deltoid muscle—the anterior, medial and posterior—and had the participants perform five of the exercises during each session. For those exercises for which a 1-RM was determined, the participants performed five repetitions using 70% of their 1-RM.

Here's what they found:

• For the anterior deltoid, the dumbbell shoulder press elicited the highest amount of muscle activation.
• For the medial deltoid, the 45-degree incline row and bent-arm lateral raise came out on top.
• For the posterior deltoid, the seated rear lateral raise and the 45-degree incline row provided the greatest muscle activation.

The bottom line is that, because of the complexity of the shoulder joint and the variety of movements possible at the shoulder, there is no one best exercise for training this muscle group. It’s impossible for a single exercise to maximally activate all three heads of the deltoid muscle at one time.

In addition, it’s vital to understand which area of the deltoid each exercise targets so that you can properly balance the workout. For example, if a routine consists of dumbbell shoulder presses, bent-arm lateral raises and the 45-degree incline row, it inadvertently neglects the posterior deltoid and doubles up on the medial deltoid.

The researchers recommend people perform the dumbbell shoulder press for the front of the shoulders and either the 45-degree incline row or the seated rear lateral raise for the back of the shoulders, pointing out that all three exercises are relatively effective at activating the medial deltoid, as well.

Finally, one last piece of advice from the researchers: It’s best to begin your workout with exercises that target the posterior deltoid, as that’s typically the weakest of the shoulder muscles, then follow up by working the anterior deltoid.

Expert Advice

In the interest of providing options for clients, we asked two experienced ACE Certified Pros to tell us about their favorite exercises for the shoulders.

Mann San Gil, who has been an ACE Certified Personal Trainer for 24 years, chose rotator cuff exercises and dumbbell shoulder presses as his go-to options. “Our rotator cuffs are often overlooked and undertrained,” he explains. “Just some simple internal/external shoulder rotation exercises go a long way in preserving our shoulder's structural integrity and help prevent shoulder impingement and other injuries.”

Dumbbell shoulder presses are a great way to work the delts while having other parts of our body engaged, including the triceps, levator scapulae, trapezius and rhomboids, he explains. One word of caution: People with current shoulder issues may want to avoid doing overhead presses and instead perform lateral raises or front raises as needed.

Cindy Sullivan, ACE Certified Personal Trainer and Group Fitness Instructor, says that two of her favorite shoulder exercises for my midlife and senior clients are the dumbbell shoulder press (seated or standing) and shoulder rainbows (light weight or no weight).

To make the dumbbell shoulder press easier, use lighter weights (or none) and perform the exercise seated for added stability. To make it more difficult, add tempo (slow on the way down), hold at the top, or do it standing with a staggered stance to engage the core.  

Shoulder rainbows are ideal for clients who are working on mobility, posture and coordination, Sullivan explains. “I use it often with those who have limited range of motion or past shoulder issues—especially when we’re easing into shoulder work without pushing too hard.”

To make this exercise easier, reduce the range of motion or perform without weights. To increase the challenge, add resistance (e.g., light weights or small Pilates balls) and slow the movement down for more control and time under tension.

Final Thoughts

Variety of movement is essential when targeting a muscle group as complex as the deltoids. According to the ACE-sponsored research, a training program that includes the dumbbell shoulder press for the front of the shoulders and either the 45-degree incline row or the seated rear lateral raise for the back of the shoulders is effective for both sports performance and function. Also, consider adding our expert recommendations to the mix. Watch this YouTube video to learn how to perform each movement used in the ACE-sponsored research, including the first four listed below:

Also, check out the links below for our expert suggestions—and be sure to share all of this information with your clients:

• Dumbbell shoulder press
• 45-degree incline row
• Bent-arm lateral raise
• Seated rear lateral raise
• Rotator cuff exercises (internal rotation and external rotation)
• Shoulder rainbows

To see all 10 exercises evaluated in the research, check out this downloadable PDF: Shoulder Exercises.

	Corrective Exercise (worth 2.5 ACE CECs): As an ACE Corrective Exercise Specialist, you will design programs for clients affected by chronic conditions or injuries, empowering them to regain daily function and move with confidence.
	Pain-Free Movement (worth 1.2 ACE CECs): As a Pain-Free Movement Specialist, you will better understand how pain affects movement and how to create new strategies to help people move without pain.