Understanding the Complex Shoulder Girdle
Properly understanding the shoulder and how it functions, coupled with the ability of technology to record and evaluate, can provide opportunity to lessen the impact on these hard-working joints in the workplace.
- By Toni-Louise Gianatti
- Sep 14, 2020
The first word that most people have on their mind when asked how their shoulders feel is tense. To have the head easily balancing on top of the spine free of gravity is something that, for most manual handling workers, is unheard of. Good shoulder organization takes a high level of awareness and proprioception (the perception of joint motion and position). Properly understanding the shoulder and how it functions, coupled with the ability of technology to record and evaluate, can provide opportunity to lessen the impact on these hard-working joints in the workplace.
The Wheel Hub
In order to manage workplace injuries or issues pertaining to the shoulder, the correct environmental and personal adjustments must be made. The shoulder girdle, also often simply described as the shoulder, consist of three main bones: the collar and upper arm bones and shoulder blades.
The shoulder has greater mobility than any other joint in the body. It enables arm movement in all three planes. To perform any lifting, pushing or pulling movement, it takes a lot of items to all work together in harmony. The shoulder contains muscles that stabilize and move the arm. To understand the workings of this well-organized apparatus, it helps to use the example, expressed by Eric Franklin, of a “wheel hub” when visualizing how it functions simultaneously.
There are three main joints in the shoulder girdle, but for the purpose of this explanation, we will focus on one—the glenohumeral joint—and note it as the wheel hub. The glenohumeral joint is a ball and socket joint where the upper arm bone attaches into the shoulder blade. So, the muscles of the shoulder girdle are arranged radically around the wheel hub of this joint. Each spoke represents a muscle. It takes a lot of effort and coordination in order for the arm to move in all directions. The spokes need to work simultaneously to pull evenly, and with the same amount of strength to maintain balance and provide a smooth ride of the arm.
A well-organized shoulder girdle has this. However, it is common to have one area pulling harder or less than the other which, if not managed, can easily be the beginning of problems.
To move with ease, or for the wheel to circle freely, consistently and with longevity, the shoulder girdle does not require a lot of strength. It requires coordination. All the muscles, tendons and ligaments that hold it all in place need to work evenly. This takes an ability to be able to sense when it is overdue for a rest and perform periodic movement changes in all directions to keep it lubricated and prevent stiffness. Most of all, strong positional and movement awareness from the host is crucial so that the latter can be adhered to.
Shoulders and Posture
One thing we tend to think about when referring to the shoulders is posture, which has a large influence on shoulder function. Habitual slouched posture might form as the result of a work pattern, emotional state, certain sports or even initiate from childhood, imitating the posture of a caregiver. A slouched posture weakens some muscles while tightening and spasming others. Weakening of the muscles supporting the shoulder, due to slouched posture, predisposes the area to problems like torn rotator cuffs and frozen shoulder. Referring back to the wheel hub, this is an example of the spokes not pulling simultaneously.
Understanding the mechanics of the shoulder, how it is best used in order to stay healthy and the technology to assist with measuring and evaluating this is game changing for manual handling workers and safety managers. Given the complexity of the shoulder, the aim is not to just redesign the workplace but to combine this with technology to help realign the girdle muscles, tendons and ligaments to create a well-oiled, spinning wheel hub for a lifetime.
This is an excerpt from an article that will appear in its full form in the November/December issue of Occupational Health & Safety. Please keep any eye out for the complete piece!