With Coach Alexa, Online Running Coach and in-person coaching in South Oxfordshire
Introduction to the Shoulder
I’m going to extend my videos on anatomy up into the shoulder today. This is the anterior, or front, view of the shoulder, looking mostly at ligaments and some of the bursa, which are shown in green.
You can see why it’s called a joint capsule for the shoulder, because it really does have this set of ligaments that basically encapsulates the whole of the little shallow ball and socket joint that we have as part of our shoulder. It is a very shallow ball and socket joint.
Mobility and Stability
Our shoulders are incredibly mobile and have huge ranges of motion compared with four-legged creatures, for example. When my dog is lying on her back asleep, her front legs are sort of sticking up in the air. We have a massive range of motion in our shoulders, but it comes somewhat at the expense of joint stability.
The ball and socket joint is much shallower than in the hip. The way the whole shoulder works – including the clavicle here, the scapula here, and the whole arm – is that the only place they’re attached to the rest of the body with a bone-to-bone joint is where the clavicle meets the breastbone. Everything else is floating and held together with ligaments, muscles and tendons, which we’ll come onto in a minute.
It’s an incredibly complicated joint, but it’s the only joint in the body where, if the muscles get tight, the whole joint moves. You see with postural tendencies that people’s shoulders are often forwards and upwards, which can have a knock-on effect on their running.
We want good, loose shoulders sitting in the right position, able to drive our arms backwards effectively for good running. Classic desk posture doesn’t really do us many favours.
Understanding the Bursa
Just to touch on these bursa here – these little things shown in green. They’re not green in reality, you’ll be pleased to know. These are cushioning, shock-absorbing pads. Their role is to make sure that everything glides smoothly over each other, with no irritation or wear caused by tendons and ligaments coming into contact with bone as our joints move.
Muscles and Ligaments of the Shoulder
Talking about the muscles and ligaments, these are two views of what’s called the deep and superficial layers – the bigger muscles on top, and the deeper, stabilising muscles underneath.
This is the front view of the torso, the front of the shoulder. Here’s the collarbone, and you can see a lot of these deep muscles and the ones that go down into the arm. The deep pectoral muscles are the big pec muscles that you see on very muscular men, but there are also lots of smaller, deeper stabilising muscles doing the day-to-day movement of the shoulder joint.
Often, in sports massage or treatment contexts, I find that these deeper pectoralis minor muscles are really quite tight in people who have desk or driving jobs, where their arms are forward a lot of the time.
Back View of the Shoulder
This next diagram shows the bigger muscles on the left and the deeper, smaller stabilising muscles on the right, from the back view. These include the lats and some of the muscles we looked at in my last couple of videos, as well as the deltoids. The deeper ones, including the triceps, are shoulder stabilisers.
There are lots of different muscles that fan out from the very top of the head of the humerus – your upper arm bone – and come down underneath and over the top of the scapula to move and stabilise this whole structure.
Again, for people with desk jobs, driving jobs, or arms-forward jobs, this whole complex – and the scapula that it attaches to – tends to slide up and outwards as the shoulders move forwards and upwards.
Comparing Humans and Animals
It’s another fascinating and complicated area of the body, and very interesting to compare ourselves with our four-legged counterparts. Their muscular and bony anatomy of the shoulder joint is in quite a different position and serves a completely different purpose.
Anyway, I hope that’s useful. Happy running.
