Gettin' all Sciency, Edition 2

Not many people know it, but Einstein used to be a crusher. Photoshop Credit: Jordan Haag. IG: @passionhorse

…so  you don’t have to.

The scientific process requires thorough (often tedious) recording of pretty much everything involved in the research process. This allows the next group of researchers to replicate the study, if need be, or continue to progress the line of thinking that spurred the original study. This results in the publishing of informative, but tedious, articles in scholarly journals. They’re tough to read, but if you put the time in, you can come away with helpful information that you can use to get stronger, stay injury free, and crush your goals.

Let’s get to it.

The Study

Shoulder Joint and Muscle Characteristics Among Weight Training Participants With and Without Impingement Syndrome

Kolber et al.  2017

The Background

The study we’re going to look at today took place recently, and examined some characteristics of Shoulder Impingement Syndrome (SIS). SIS is an umbrella-ish term that is used to describe certain instances of shoulder pain. Sometimes, if certain movement or structural characteristics are out of whack, the Rotator cuff tendons or the sac of fluid that separates these tendons from bony structures in the shoulder might get stuck or pinched by these bony structures when reaching overhead. Over time, this can lead to degradation of the Rotator cuff soft tissues and that fluid sac (Subacromial bursa, if you want the scientific term). Persistent shoulder pain is usually the inevitable destination of that road.

The researchers involved in this study wanted to see if there was a trend with certain muscle strength and range of motion characteristics among people with Impingement Syndrome, and were curious if any differences existed for people without Impingement Syndrome.

How They Did It

The researchers selected 55 male adults with ages from 21 to 56. The average age was 27 years old. All subjects had been strength training 2-5 times a week for an average of 9 years, so all subjects were relatively seasoned lifters. They were separated into two groups, those with Shoulder Impingement, and those without.

To determine whether a subject had Impingement or not, two tests were administered. –

-Hawkins-Kennedy Test.

***DON’T just have your friend do this. This is a hands-on test meant for use by a clinician that provokes pain to get a diagnosis. If you don’t have the word “Doctor” in front of your name, you shouldn’t be doing this to someone. End Rant.***

The second test looked for a pain during a shoulder arcArc

If these tests were positive for pain, the subject was placed in the Impingement group. If the tests were negative, and the subject had experienced no pain for the previous 72 hours during training or daily living, they were placed in the Non-impingement group.

There were three areas of testing: Muscle Strength, Muscle Strength Ratios, and Active Range of Motion

Muscle Strength

The first attribute tested was muscle strength. The researchers looked at five muscle group’s strength levels, using a hand digital dynamometer. These muscle groups were the shoulder abductor group, external rotators, internal rotators, and the upper and lower trapezius muscles.

Muscle Strength Ratios

After these values were obtained the ratios of these groups’ strength levels were compared with one another. The relationships examined were:

-Internal Rotator Strength to External Rotator Strength

-Shoulder Abductor strength to External Rotator Strength

-Upper Trapezius Strength to Lower Trapezius Strength

Active Range of Motion

The researches examined each subjects active flexion, abduction, external rotation and internal rotation using a goniometer, a device used to measure joint angles.

External and Internal Rotation


After all the data had been collected, certain trends existed.

-Shoulder External Rotators and the Lower Trapezius muscles were significantly weaker in individuals with Impingement Syndrome compared to individuals without.

-The strength ratio of Internal Rotators vs. External Rotators was significantly skewed towards Internal Rotators (Internal Rotators were way stronger than the external rotators) in individuals with Impingement.

-The strength ratio of Abductors vs. External Rotators was significantly skewed towards the Abductors in individuals with Impingement.

-The strength ratio of Lower Trapezius vs. Upper Trapezius was significantly skewed towards the Upper Traps in individuals with impingement.

-Individuals with Impingement had significantly less Internal AND External Rotation than individuals without impingement.


-One takeaway from this study is the importance of shoulder external rotator and lower trapezius strength. Keeping these muscles and groups of muscles strong help keep the “ball” of the humerus centered in the shoulder socket. The shoulder relies on a relatively large amount of soft tissue to keep the joint centered, so a weakness in certain groups may allow the ball to creep out of the center position. Poor position means a higher chance of running out of room during a movement, and therefore a higher chance of trapping soft tissue and getting impingement. It seems external rotators and lower traps tend to be weaker in individuals with impingement, so it miiight be a good idea to keep them strong. Here are some simple and effective exercises to address that.


-Another takeaway I got from this study was discrepancy in strength that was related to shoulder impingement.

It’s seems as if people can be pulled into internal rotation if they neglect proper form during training, or have certain lifestyle factors, such as sitting at a computer for extended periods of time, drive for extended periods of time, or have poor posture (the standard climber hunchback). All these can lead to an imbalance in which our joint position and muscle strength is skewed towards shoulder internal rotation and lead to a weakness in our external rotators.

Another factor seems to be the imbalance between lower trap and upper trap strength. We’ve gone over a way to work on lower trap weakness, but the upper traps can end up being to “switched on”  by something we do every day:Breathing. When we breathe incorrectly, it’s often by using our accessory muscles which are in our shoulders, upper traps, and neck. Ideally, we want to be using our diaphragm to pull air into our lungs, and crocodile breathing is a great way to reinforce this pattern. Lay on your belly and take relaxed, complete inhales through your nose. Your midsection should rise and expand laterally, and your shoulders should stay relaxed.


Wrapping it Up

Give some thought to how you breathe and what positions you spend the majority of your day in. If there’s some things you can work on, start doing them! The examples I talked about in the videos are just a few of the myriad of ways you can begin to address these issues.

I think these exercise form corrections are crucial to the health of the shoulder joint, as strength training with proper form helps reinforce movement characteristics. You’re either building bad habits and making them harder to break, or you are reinforcing healthy and balanced joint mechanics. You make the choice.

Have questions, comments, rants and raves related to this article? Feel free to reach out to me!

Learn More

Here’s the citation and link to the abstract if you want to read the full study.

Kolber et al. Shoulder Joint and Muscle Characteristics Among Weight Training Participants With and Without Shoulder Impingement Syndrome, Journal of Strength and Conditioning Research

doi: 10.1519/JSC.0000000000001554