The shoulder is a complex joint. It is a shallow ball and socket joint. The only attachment of the upper arm bone and shoulder blade to the torso is where the clavicle or collar bone joins to the sternum; the sternum is the dagger shaped bone in the centre of the ribcage. This gives our arms a great amount of freedom of movement, but it also means that the muscles surrounding the shoulder joint also stabilise it. In comparison, the hip joint is also a ball and socket joint, but it is deep; the upper leg bone cannot easily pop out of that joint. So the muscles that surround the hip joint have an easier time stabilising the joint.
The muscles deepest to the shoulder joint are called the rotator cuff muscles and their principal job is one of stabilisation. They help turn the upper arm bone inwards, outwards or start the movement that lifts the arm away from the side. Each movement presents its own set of problems. The muscles that rotate the arm inwards tend to be dominated by the large movement muscles that also do this job, namely the pecs and the lats – the big muscle of the chest and the big pulling muscle that runs down the back from the armpit to the bottom. As a result, the smaller and deeper inward rotating muscles can end up short, tight and weak. A good remedial masseuse will sort this out. How do we know this is a problem? Well if we hold a pen or pencil in each hand and stand with our arms beside our body, palms facing inwards, the pens should be pointing straight forwards. If they are turned inwards, this indicates a problem in shoulder alignment that needs addressing before injury occurs.
The muscle that lifts the arm away from the side gets squeezed if our shoulders are lifted, as the blog on impingement went into. How do we know we have a problem here? Starting from palms touching the outside of the thighs, slowly lift the arms straight out to the sides. Any pain or need to give them a bit of a swing to get them going indicates that muscle is not working properly and needs attention before an injury occurs.
Finally we have the external rotator cuff muscles, a pair of small muscles that externally rotate the upper arm bone. These muscles end up weak in the huge majority of people because of life style leading to rounded upper back posture. Sitting at a desk, head poked at the computer screen or pouring over some writing; driving; pushing buggys; telly slumping all contribute to the upper back becoming rounded. The head pokes forwards, and, bearing in mind the head weighs about 3.5 – 5.5 kgs or 8 – 12 lbs, places strain on the muscles that hold the head in place, some of which also lift the shoulders upwards. And so we end up with a rounded upper back and lifted shoulder blades which makes it difficult for the external rotator cuff muscles to work properly. And added to this is the fact that we don’t often take our arms into external rotation either as a simple movement or when moving things about. We push much more than we pull. This is partly why gardening is a) very good for us and b) can cause shoulder injury. How do we know we have a problem here? Unless we have perfect posture, we can assume weakness here. From my years of experience traning people, I personally would say that until we are pretty close to perfect posture, it is very hard to properly strengthen this muscle group. They will strengthen a bit, especially if they are very weak due to injury.
So in order to stabilise the shoulders to avoid pain either at the shoulder, elbow or wrist, continuous work must be done to straighten the upper back and regain its ability to bend backwards. At the same time, continuous work must be done on tight chest muscles such as the pec minor that rolls the shoulders forwards and down. And when pushing care must be taken to engage both the lower trapezius and the serratus anterior. So here is a brief chat about them.
The muscle in bright red is the trapezius muscle. We can see it runs up to the bottom of the skull and down to the bottom of the thoracic spine (this is the part of the spine that runs through the ribcage area). The fibres of the muscle run upwards, inwards and downwards. What happens in this muscle is that the upper part of the trapezius gets short and tight, lifting the shoulders upwards and inwards (along with other muscles, all acting like a bunch of cronies), which pulls the shoulder blade up and out of position. Now as the arms lift upwards, ideally the lower part of the trapezius, the fibres that run downwards, engage and help stop the shoulder blade from lifting upwards unnecessarily. When this happens all the muscles surrounding the joint can engage properly in their job – whether stabilising or moving the arm. When it doesn’t happen, none of the muscles surrounding the shoulder joint can engage properly and we end up with shoulder instability, being weaker than we should be and leading to eventual pain and injury. So it is important to strengthen this muscle. The easiest exercise to do is the first part of the lat pull down.
The only upper body exercise type that does not engage the lower trapezius is the shrug type.
The other major stabiliser of the shoulder is the serratus anterior – also known as the boxer’s muscle. It is a funny looking muscle. It attaches on the inside of the shoulder blade and runs in 8 fingers onto the top 8 ribs. It pulls the shoulder blades onto the ribs at the back,it rotates the shoulder blades upwards when the arms are lifting forwards of the body line and it also it pulls the shoulder blades forwards around the rib cage. It is this latter movement that is so important for boxers when punching.
The activities that it is important to engage it in apart from punching, are doing press ups, any pushing activity either in front of the body or overhead – or any kind of ab work when the body weight is on the arms and toes or knees (or handstands, come to that). This stops the shoulder blades from winging off the back of the ribcage . Just as with the lower trapezius, an overactive upper trapezius muscle plus cronies will make it very difficult to engage. The classic exercise that is supposed to fire this muscle up is press ups on the wall. If you can’t make this exercise work for you, it will cheer you to know that I have had to devise my own exercise to wake it up since I regard push ups on the wall as fairly pants at this job.
So the exercise of the week: Swiss Ball mountain climbers should work both the serratus anterior and the lower trapezius, as should the bench press, press ups and the plank. To avoid injury and increase strength we must make sure these 2 muscles are active. As they get stronger and the shoulders migrate to a better position, then we can also make very good progress strengthening the external rotator cuff muscles. Not only will we be stronger and more injury resistant as a result, our posture will have improved greatly. We will be taller and look just so much slimmer and, perhaps suprisingly, more relaxed.