I mentioned in a previous post that a piriformis muscle that is in spasm can influence the shoulders. I've been asked to try and explain the link.
Now there are a few things you need to understand.
The first thing you need to know is that all muscles work in pairs. So when one muscle contracts the opposite muscle has to relax (If it didn't then the joints would not move). This contracting of one muscle (the agonist) and relaxing of the opposite (antagonist) is referred to as reciprocal inhibition.
There is also something called altered reciprocal inhibition. This is where when one muscle is overactive 'strong' the opposite muscle becomes inhibited 'weak'. Now when I say weak and strong I don't mean in the strength sense. I mean weak and strong in the sense that the nerves are firing enough to contract the muscles.
Ok so the next thing you need to know is that there are also muscles around the joint which contract to support the movement. These are called synergists.
So imagine that you are doing a leg curl so that your foot comes to kick your bottom. The agonist which is contracting would be the hamstrings. The antagonist which is relaxing would be the quads. Then the synergists which assist the movement would include the calf muscles (amongst others).
Now there are occasions (posture, injury, etc) when the main mover (agonist) is overworked and decides to take a holiday. As a consequence the synergists have to pick up the slack to cover for them. This is referred to as synergistic dominance.
Now for a few days this would be fine. But think of if it was you. If the boss was overworked and took a holiday and then you had to take over for a while I'm sure you could cope for maybe a couple of weeks or so. But after a while, all the stress and strain that your boss went through is passed to you and in the end you need to take a holiday too. Alternatively your boss decides to come back but you don't want to stop what you're doing. So you can see just how these problems occur and have an impact.
Right so think of this.
If I sit down all day my glutes become 'weak' and as a consequence the synergists (piriformis) takes over. Now the glutes are connected to the opposite shoulder via the thoracolumbar fascia. So if my glutes are not firing correctly then the opposite shoulder can be impacted. So the piriformis can potentially be preventing the glutes from activating (think synergistic dominance) and as consequence affects the shoulder.
Therefore if we release piriformis, activate the glutes then potentially the shoulder issues can be resolved.
(Note if you just try and activate the glutes without inhibiting the piriformis first then the piriformis will continue to dominate).
Now this is one theory. And each case is different. But what I can say for certain is that I know the connection is there between the pelvis and the shoulder. Just today I witnessed the pelvis go from not moving correctly to doing what it should by releasing the pec minor (a muscle at the front of the shoulder which moves the scapula).
If you study the anatomy enough, if you understand the concepts of kinetic chains, of reciprocal inhibition and of synergistic dominance you can see just how connected the body is and how sometimes we need to take a step back in order to see the bigger picture. Sometimes we need to be a detective and work out just where the connections lie.