2 Tests to Help Determine if One Shoulder Is Stronger Than the Other (and 3 Exercises to Fix It)

Having one shoulder stronger than the other is a common muscle imbalance.
Image Credit: Joel Sorrell/E+/GettyImages

In an ideal world, we would all have perfectly balanced strength and crush workouts left and right. But here in the real world, however, many people struggle with muscular imbalances that make certain movements extra challenging.

Shoulder imbalances are particularly prevalent, says Kasia Gondek, physical therapist and certified strength and conditioning specialist at Fusion Wellness and Physical Therapy. It's common — but not normal — for one shoulder to have less strength, activation or coordination than the other, Dr. Gondek says.

"If you are right-handed and someone asks you to sign your name with your left hand, you would certainly notice that signing your name is more difficult, and it looks quite different than if you were signing with your dominant hand," she says. "The same concept applies to our shoulders and arms."

Maybe you've noticed one shoulder tires out more quickly than the other, or perhaps one shoulder reaches its lactic acid threshold (i.e., feels the burn) faster than the other. If you've come to accept this as your version of normal, hold on just a minute: Dr. Gondek warns that unfixed muscle imbalances can stall your fitness progress and, in a worst-case scenario, lead to injuries.

The good news is you can bring your weaker shoulder up to speed with your stronger one. Just try the test below to find out which shoulder is weaker, then practice the following three exercises to help fix the imbalance.

5 Signs One Shoulder Is Stronger Than the Other

You might already have an inkling that one of your shoulders is stronger than the other.

"Throughout our daily activities, we tend to use our dominant arm or shoulder more often simply because it is better at doing things we need to do," Dr. Gondek says. "This isn't a problem in general, except when we do more demanding activities such as weightlifting or playing sports."

Watch for one (or all) of these five potential indicators that one shoulder is stronger than the other:

  1. During a shoulder press, one shoulder raises faster and with less effort
  2. During a push-up, one shoulder lowers sooner than the other
  3. One shoulder feels less stable during workouts or when carrying something heavy
  4. One shoulder has pain or stiffness and the other doesn't
  5. One shoulder feels more mobile or flexible than the other

How to Test for Shoulder Muscle Imbalances

First, a bit about your shoulder anatomy. Nine main muscles attach to your shoulder joint, and four of those make up your rotator cuff. Also, the shoulder moves in three planes of movement: forward and backward (flexion/extension), out and in (abduction/adduction) and turning inward and outward (internal/external rotation), Dr. Gondek explains.

Because so many muscles impact overall shoulder strength and coordination, there isn't just one simple test to figure out if you have a shoulder imbalance, Dr. Gondek says. A physical therapist would normally conduct several different tests to pinpoint specific imbalances.

However, these two quick tests can help you determine whether one shoulder is, in general, weaker than the other:

Test 1: Prone Internal and External Rotation

  1. Lie on your stomach at the side of a massage table, sofa or bed so that the front of your shoulder and your arm aren't touching the supporting surface.
  2. Bring your arm out to the side so it's in line with your shoulder, elbow bent at 90 degrees.
  3. Rotate your arm so that your palm and forearm move up (like a goal post). Your palm will end up facing the floor (external rotation).
  4. Next, move your palm and forearm downward so that your palm faces the ceiling (internal rotation).
  5. Note how far you can move and if there's any pain.
  6. Complete steps one through six on your other arm and compare your results.
  7. Challenge yourself by adding a hand weight and see if you can keep the same range of movement without shrugging your shoulders or straining your neck or back.

If you notice that your range of movement is more limited on one side or you can't perform the test with the same weight on both arms, you may have an imbalance of your rotator cuff muscles, Dr. Gondek says.

Test 2: Front Plank With One-Arm Lift-Off

Recruit a friend to observe your shoulder blades while you perform this two-part test that challenges the muscles used for overhead reaching and shoulder stability.

  1. Begin in a high plank, hands under your shoulders. Keep your arms straight but not overextend.
  2. Part 1: If the person observing your shoulder blades sees them "winging" or poking out from your rib cage in the back, you likely have weakness or poor activation of the scapular muscles, Dr. Gondek says. The test stops here if you can't keep your shoulder blades flat along your rib cage.
  3. Part 2: Begin in the same position. (Make sure you keep your shoulder blades against your rib cage.) Next, shift your weight onto your dominant hand and hold for 3 to 5 seconds. Repeat this on the non-dominant side. If your observer notices your shoulder blades "winging" or protruding on one side but not the other, you likely have weakness or stability issues in that shoulder, Dr. Gondek says.

3 Exercises to Help Fix Shoulder Imbalances

If it turns out that one of your shoulders is stronger than the other, it's important to strengthen your weaker side to avoid injuries. As a bonus, you'll see overall strength improvements when your shoulders are balanced.

The best way to fix a shoulder imbalance is to focus on strengthening unilateral movements, a.k.a. one-armed exercises, says Chad Walding, physical therapist and co-founder of NativePath. "Always complete the exercise with the weak arm first and see how many reps you get," Dr. Walding says. "Once you complete the weak side, do the exact same amount of reps on the strong side. This will allow the weaker side to catch up."

Try these three unilateral shoulder exercises:

1. Single-Arm Dumbbell Press

  1. Choose a dumbbell that's challenging but not so heavy that you can't press it overhead without arching your back. Your spine should stay stable and neutral.
  2. Hold the dumbbell in one hand by your side. Hoist it up to assume the front-rack position (one bell of the dumbbell should touch your shoulder).
  3. Press the dumbbell overhead in a smooth, controlled motion, fully extending your shoulder and elbow at the top. Keep your arms close to your head: Your biceps should graze your ear in the top position.
  4. Lower the dumbbell back to your shoulder.
  5. Complete 8 to 10 reps on your weaker shoulder, then follow with the same number of reps at the same weight on your stronger shoulder.

2. Supine Dumbbell External and Internal Rotation

  1. Choose a lighter dumbbell. Lie on your back on a bench with your shoulder not touching the surface.
  2. Position your arm so that your elbow makes a right angle: Put your elbow in line with your shoulder and your wrist in line with your elbow.
  3. Hold the dumbbell straight up. From there, slowly lower the back of your hand to bring your wrist level with the bench. You should feel tension in the back of your shoulder.
  4. Raise the dumbbell back to the starting position.
  5. Complete 8 to 10 reps on your weaker shoulder, then follow with the same number of reps at the same weight on your stronger shoulder.

3. Single-Arm Front Raise

  1. Choose a light dumbbell. Hold it in one hand with your palm facing your thigh.
  2. Brace your core and, keeping your elbow fully extended, raise the dumbbell up until your arm is parallel with the floor. Keep your palm facing downward.
  3. With control, lower the dumbbell back to the starting position.
  4. Complete 8 to 10 reps on your weaker shoulder, then follow with the same number of reps at the same weight on your stronger shoulder.

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