Updated: May 5, 2022
Have you ever been to physical therapy for a shoulder injury? If so, you have probably done the exercise pictured below:
Now, you may have done it lying on your side (which research shows actually creates greater rotator cuff activation), but the point of the exercise is similar.(1) You are trying to activate your rotator cuff muscles. Before we get too into the weeds, let’s quickly review your rotator cuff and what it does.
If you remember a previous post about shoulder impingement that I wrote a couple of weeks ago, the shoulder is a very loose joint. It has more mobility than any other joint in the body because it is essentially a golf ball on a tee. The lack of support leads to mobility, but it puts a greater demand on the surrounding muscles.
The rotator cuff is a collection of four muscles that provide significant stability to the shoulder joint.
You have three rotator cuff muscles on the back of your scapula (supraspinatus, infraspinatus, and teres minor) and one on the front (subscapularis). The tendons of these muscles converge and attach to the outside part of your humerus. They create a suction force, to hold the head of the humerus in place. The lack of bony stability for the shoulder makes the rotator cuff muscles pretty important for stability and hence mobility of the shoulder. If you are unable to stabilize the humeral head, then it can be difficult or painful to move.
An interesting point that we shouldn’t forget (once again mentioned in the impingement post) is that the rotator cuff does not have the perfect relationship to pain and function that we all assume. A study showed that 17% of shoulders with no issues had rotator cuff tears based on MRIs. Also, 17 out of 18 people re-tore their rotator cuffs after surgery, but 16 still reported decreased pain!
All this is to say that our bodies are not as simple as we think. Too often we think of the human body as an automobile. Nowadays, they can use a scanner on your car and figure out the exact part that is malfunctioning. Replace the part and your car is running smoothly. The human body is not like that at all. MRIs can be misleading, as I have seen people with great MRIs in excruciating pain and vice versa. It can be easy to become fixated on an MRI which says that your supraspinatus was torn. We then think, “If I fix that, then I will be better”. This is rarely the case.
It is important to review what a muscle tear actually is. Most people hear that they have torn a muscle and think it is literally hanging off the bone. Rotator cuff tears are termed small, medium, large, and massive (talk about fearful language!). A small tear is less than 1 cm, medium is 1-3 cm, large is 3-5 cm, and massive is over 5 cm. Did you know that the average supraspinatus ranges from 12.4-16.8 cm?(2) So a massive tear may be only 1/3 of your supraspinatus! That still seems like a lot, but let’s think of a different point.
There are two ways to tear your rotator cuff: traumatically or atraumatically. Traumatic tears are usually from falls. (3) Atraumatic tears are typically what we would call wear and tear injuries. Imagine the wearing away of your rotator cuff muscle. Every day you wake up and can lift however much weight you want or reach as far as you want, until one day you cannot. The tear progressed to the point of limiting your activities of daily living. You have two options at this point: try and repair the tear (I mentioned before how these surgeries often result in re-tears) or strengthen what is left. If a massive tear means that 2/3 of your muscle is left, I would want to try strengthening that. After all, you don’t need to press 300 pounds over your head, you just need it to be a little stronger or let you reach a little further.
So, let’s look at the first picture again. External rotation exercises like this one provide excellent electromyography (EMG) results for the rotator cuff muscles, particularly your infraspinatus. An EMG is when they either put sensors on your skin or use a needle to put them right in the muscle, they have you do different activities, and they see how much the muscle activates for each movement. An important note is that EMG studies show what percent of maximal activation your muscle achieves, not how strong it is.
Now I think that starting with external rotation exercises can be helpful in rehabilitation. They provide activation of the muscle which promotes blood flow and nerve recruitment. A good concept is the use it or lose it principle. If you never use a muscle, it gets weak and you lose nerve connections. However, basic exercises can maintain neural involvement and provide some pain relief. It is amazing how often a muscle feels better if we gently use it.
A question to ask yourself with all exercises is: is this difficult because I am improving myself, or is this difficult for the sake of being difficult? It is very easy to come up with a million exercises that will have you feeling weak. For example, imagine holding 5 pounds over your head for as long as you can. Your shoulder will be exhausted by the end of it. However, unless you work in a job where you have to hold light weights over your head for a long time, is that really a good exercise for you? Similarly, unless you are learning a strange Tik Tok dance that involves moving your shoulders in weird ways, are you ever performing the motion in the first picture?
What do we actually need our shoulders to do? We need them to reach overhead to grab stuff, lift stuff, push stuff, and pull stuff. That is a simple way to look at how our shoulders move. Now imagine I said that you need to lift a box over your head to put it away in your garage. Do you think that any amount of external rotation exercises will achieve that?
A research study showed that rotator cuff muscle activation increased with greater loads when it came to push-ups and similar exercises. (4) Isolation exercises can be good for the beginning of rehabilitation and if you are an expert weightlifter, but other exercises can be more beneficial for people in-between. Think of giant weightlifters: how do you think they get strong shoulders? They do bench press, rows, overhead press, and other exercises. At the end of their workout they may do individual exercises like external rotation, but that is not what makes them strong.
There comes a point where you cannot lift more weight with external rotation exercises. If you are lying on your side, anything more than 10-15 pounds can be very difficult. However, you need to lift more than 15 pounds in life. Now it is time to transition to more functional exercises. While these exercises might not isolate the rotator cuff muscles, they sure are using them. Imagine the man in the picture above not being able to stabilize his humerus. He would not stand a chance of lifting that weight. He is getting a great rotator cuff workout.
Another benefit to incorporating more “functional” exercises is that they work on the timing of your muscles. If your rotator cuff only learns to activate with a small weight when lying on your side, how is it going to stabilize when you go overhead? You need to gradually expose your body to loads in different positions to allow adaptation and strengthening to occur. This will also help develop the surrounding muscles in your shoulder, which should not be neglected in rehab!
So, what should rehab look like when you are coming back from a shoulder injury? It may start with light weights concentrating on the rotator cuff to improve neural connections. However, this is just the beginning and a point that many consider physical therapy to be done. The first time you lift something heavy over your head should not be at home, it should be at PT. We can target certain muscles in the shoulder, but at the end of the day rehab should be about getting you back to doing whatever you want safely and easily.
1 Reinold MM, Wilk KE, Fleisig GS, et al. Electromyographic analysis of the rotator cuff and deltoid musculature during common shoulder external rotation exercises. J Orthop Sports Phys Ther. 2004;34(7):385-394. doi:10.2519/jospt.2004.34.7.385
2 Volk, Albert G. MD; Vangsness, C. Thomas Jr. MD An Anatomic Study of the Supraspinatus Muscle and Tendon, Clinical Orthopaedics and Related Research: March 2001 - Volume 384 - Issue - p 280-285
3 Mall NA, Lee AS, Chahal J, et al. An evidenced-based examination of the epidemiology and outcomes of traumatic rotator cuff tears. Arthroscopy. 2013;29(2):366-376. doi:10.1016/j.arthro.2012.06.024
4 Uhl TL, Carver TJ, Mattacola CG, Mair SD, Nitz AJ. Shoulder musculature activation during upper extremity weight-bearing exercise. J Orthop Sports Phys Ther. 2003;33(3):109-117. doi:10.2519/jospt.2003.33.3.109