Joints are amazing biomechanical structures. Comprised of a union of two or more bones, stabilizing and connecting ligaments, as well as muscles and their tendinous attachments, joints allow you to move your body freely. Without joints, your skeleton would be rigid. Imagine trying to do burpees without bending your knees – or your hips or elbows, for that matter!
There are three types of joints in the human body. Each type of joint has different functions and structures. The three joint classifications are:
- Fibrous joints – this type of joint is immovable. Examples include the plates that make up the skull.
- Cartilaginous joints – made up of bones connected by cartilage, this type of joint can be described as slightly moveable. Examples include the spine.
- Synovial joints – described as freely moveable, synovial joints are characterized by a fibrous capsule and a synovial fluid-filled joint cavity. There are several types of synovial joints, including hinge joints (elbows and knees), and ball and socket joints (hips and shoulders).
You may be thinking that your spine is more than just slightly moveable but, compared to a synovial joint, this is an accurate description. Your spine can bend and rotate between 30 and 80 degrees, depending on the section of the spine and direction of movement. In contrast, your knee can bend through around 180 degrees while your shoulder has 360-degree movement.
Unfortunately, the more mobile a joint is, the less stable it tends to be. That’s why shoulder joint problems, pain, and injuries are so common and are the focus of this article.
Shoulder joint anatomy
As stated, the shoulder is a ball and socket joint. It is controlled by a large number of muscles and is the most mobile joint in the human body. The muscles that control the shoulder joint include:
- Biceps
- Triceps
- Pectoralis major
- Latissimus dorsi
- Anterior, medial, and posterior deltoid
- The supraspinatus, infraspinatus, teres minor, and subscapularis (AKA the rotator cuff)
Because so many muscles affect the shoulder joint, treating shoulder injuries is rarely straightforward. It’s also very hard to rest a painful shoulder joint as it’s involved in almost every exercise you do, as well as many everyday movements. That’s why shoulder injuries are so disruptive and, in some cases, can even be career-ending.
The movements available at the shoulder joint are:
- Flexion – raising your arm forward
- Extension – pushing your arm backward
- Abduction – lifting your arm out to your side
- Adduction – drawing your arm down and into the side of your body
- Circumduction – a cone-shaped circular movement
- Medial rotation – turning your arm inward
- External rotation – turning your arm outward
All of these muscles and movements mean that the shoulder is inherently unstable. That’s why you wobble when you lift and hold a weight above your head, but the same load has much less impact on your knees, hips, or even your spine.
Of all the movements that the shoulder can do, medial and external (also known as lateral) rotation are the most problematic.
How shoulder rotation affects athletic performance
Shoulder strength and mobility can have a huge impact on athletic performance. Tight shoulder rotators will limit your range of motion. In the case of reduced external shoulder rotation, this could mean you can’t “wind up” as much as usual before a throw or serve or can’t get the bar low enough on your back during squats. Overhead squats and shoulder presses are also much harder when you are medially rotated.
Lack of rotational strength increases your risk of acute and chronic injury. Your shoulders won’t be as stable as they should be and, considering the shoulder joint is already inherently unstable, that’s a recipe for problems. Lack of rotational strength can cause injuries during training or competition, or long-term as a result of improper shoulder alignment.
Bottom line: it would be a mistake to underestimate the importance of shoulder rotation, both in terms of performance and joint health. Keeping your shoulders in good working order won’t take up too much of your time, but that small investment will come back to you ten-fold. Not only will you perform better, you should also suffer fewer injuries – both chronic and acute.
Balance is everything
Muscles are mostly arranged in pairs on opposite sides of joints. Examples include:
- Biceps and triceps – upper arms
- Quadriceps and hamstrings – upper leg
- Gastrocnemius and tibialis anterior – lower leg
- Rectus abdominus and erector spinae – midsection
When one muscle contacts and shortens, the muscle(s) that oppose it relax and lengthen. In general, opposing pairs of muscles should be fairly equal both in terms of strength and flexibility. If there is an imbalance, the function of the joint may be compromised.
In the case of the shoulder, a lot of people have very strong and/or tight medial rotators, but weak/lengthened external rotators. This can lead to changes in range of motion and posture. For example, if you have tight medial rotators, your shoulder may naturally come to rest in a medially rotated position and gravitate toward that position during activity. This puts your shoulder in a mechanically disadvantageous position, which can affect both the bony structure of the joint and the soft tissues within.
When medially rotated, things like overhead movements are often painful, and soft structures are pinched between the bones that make up the shoulder joint. This can lead to inflammation and pain. Impingement syndrome is one such example.
Medial rotation dominance is a common problem. There are several reasons for this.
- Most upper body exercises involve medial rotation, including push-ups, pull-ups, and overhead presses.
- External rotation movements are much rarer and less likely to be programmed progressively. No one knows what their one-repetition maximum is for external cable rotations but invariably know how much they can bench press!
- Driving and working at a keyboard put you into a medially rotated position for extended periods. This stretches and weakens the muscles responsible for external rotation.
- Very few people address shoulder strength/mobility imbalances until they have a problem. Rehab is common, but prehab is not.
Assessing shoulder mobility and strength
If you have shoulder problems, you should contact a qualified medical practitioner, such as a physiotherapist, for help. This information is not meant to replace professional advice.
Testing basic shoulder mobility is a relatively straightforward process. Every athlete should do these tests to see if they are at risk of developing shoulder problems or to identify possible reasons for current shoulder pain. Remember to test both shoulders, even if you only have pain on one side. Left-to-right imbalances can cause problems too.
Testing external rotation mobility
Lie on your back with your legs bent and your feet flat on the floor. Place your upper arm on the floor at 90-degrees to your body. Bend your elbow and straighten your fingers. Without allowing your shoulder or upper back to lift, lower the back of your hand down toward the floor. You should be able to achieve 80-90 degrees of external rotation. The back of your hand should come close to touching the floor.
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Testing internal rotation mobility
Lie on your back with your legs bent and your feet flat on the floor. Place your upper arm on the floor at 90-degrees to your body. Bend your elbow and straighten your fingers. Without allowing your shoulder or upper back to lift, lower your palm down toward the floor. You should be able to achieve 60-70 degrees of internal rotation. Your hand should be roughly the same height as your body.
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Testing external rotation strength
Take a resistance band and shut one end in a door or attach it to an anchor set to about mid-abdomen height. Stand sideways on to your anchor and grab the band on your furthest hand. Bend your elbows to a right-angle. Tuck your upper arm into your side. From this position, and while keeping your elbow bent to 90 degrees, rotate your shoulder outward against the resistance offered by the band. Do several reps to determine your strength. Move further away from your anchor point to increase the tension.
Testing internal rotation strength
Take a resistance band and shut one end in a door or attach it to an anchor set to about mid-abdomen height. Stand sideways on to your anchor and grab the band on your nearest hand. Bend your elbows to a right-angle. Tuck your upper arm into your side. From this position, and while keeping your elbow bent to 90 degrees, rotate your shoulder inward against the resistance offered by the band. Do several reps to determine your strength. Move further away from your anchor point to increase the tension.
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Without a dynamometer, which is a device for testing strength, you’ll have to rely on how these two exercises feel to determine your strength. Ideally, the amount of force you can generate should be similar for both internal and external rotation. Large imbalances in strength or range of motion increase your risk of injury and could also affect your performance of many exercises.
Addressing shoulder mobility and strength imbalances and deficits
Once you have completed these rudimentary tests, you should have an idea of whether you need to stretch or strengthen your shoulder rotators. You may even need to do both. Deficits in shoulder mobility and strength should be addressed even if you don’t have any should injuries or pain. An ounce of prevention is worth a pound of cure, and taking action now could save you months of frustrating rehab in the future.
Tight shoulder rotators should be gently stretched several times per day. You should also stretch them before and after training, as well as after periods of inactivity, such as working at your desk or driving for several hours.
The tests you used to assess shoulder mobility are also good stretches. Use your non-working arm to gently increase your range of motion. Ease slowly into each stretch and never force it. As lying down may not always be practical, you can also do these stretches sitting or standing. Just make sure you keep your shoulder joint pulled down and back so that any movement is the result of medial or lateral rotation only.
Additional stretches include:
1. Doorway stretch for internal rotators
- Stand in an open doorway. Bend your nearside arm to 90 degrees and place your hand on the doorjamb. Tuck your elbow into your side and hold it there with your free hand.
- Gently turn your upper body away from the doorway to stretch the internal rotations. This means you’ll be taking your shoulder into external rotation.
- Hold this position for 30-60 seconds and then swap side.
2. Broomstick stretch for internal rotators
- Hold a broomstick in front of you using an overhand grip. Bend the arm you want to stretch to 90 degrees and tuck your elbow into your side.
- Use the broomstick to gently push your arm out and away to stretch the internal rotators.
- Hold this position for 30-60 seconds and then swap sides.
3. Cross-over stretch for external rotators
- Place your left hand on your right shoulder so your arm is parallel to the ground.
- Hold the back of your left arm with your right hand.
- Gently pull your arm across your body to stretch the external rotators located in the back of your shoulder.
- Hold this position for 30-60 seconds and then swap sides.
4. Behind the back stretch for external rotators
- Bend one arm and place your hand behind your back. Your palm should be facing outward.
- Reach across the front of your body and grip your upper arm.
- Gently pull your upper arm forward and into internal rotation.
- Hold this position for 30-60 seconds and then swap sides.
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If your shoulder rotators are weak, perform strengthening exercises every other day. Do 2-4 sets of 8-15 reps of your chosen exercise. As before, the exercises you used to assess shoulder strength are also ideal exercises for increasing it. Remember to make your workouts progressive, i.e., gradually increase the number of reps, sets, and the resistance to make your shoulder rotators stronger.
Additional strengthening exercises include:
1. Dumbbell L flyes for internal rotators
- Lie on your side on an exercise bench. Make sure your shoulders are square and stacked.
- Bend your bottom arm to 90 degrees. Hold a dumbbell in that hand.
- Rotate your arm inward and lift the dumbbell up to your opposite shoulder.
- Lower the weight and repeat.
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2. Cable machine internal rotation
- Set the handle on a cable machine to about waist height. Attach a D-shaped handle to the cable. Stand sideways on to the machine.
- Hold the handle in your nearside hand. Tuck your elbow into your side.
- Without bending or straightening your arm, rotate your arm inward and across your body.
- Lower the weight and repeat.
3. Seated dumbbell external rotation
- Sit on the floor or an exercise bench. Bend one leg and rest your elbow on your knee. Hold a dumbbell in that hand.
- Bend your elbow to 90 degrees.
- Lower the dumbbell forward and down toward the floor and then lift it back up until your forearm is vertical.
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4. Two-handed band external rotation
- Hold a resistance band in front of you. Bend both arms to 90 degrees and tuck your upper arms into your sides.
- Without moving your arms away from your body, rotate both arms out and stretch the band across your abdomen.
- Return to the starting position and repeat.
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Conclusion
The shoulder is an amazing joint, and it’s involved in every upper body movement you perform. However, it is also prone to instability. That’s the price you have to pay for so much mobility. Like any complex machine, there are a lot of things that can go wrong with your shoulder, and those problems can sometimes be severe. However, assessing and then addressing medial and external shoulder strength and mobility can boost performance and may even prevent injuries too.
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