Sep 2015 26

Pec minor

By: Dave Wheeler

Most of us know about the "pecs" - officially pectoralis major, the chest muscle that gym-goers want to build up when they do chest-presses. But there's a little known muscle that's part of the same group, called pectoralis minor which can be a real bugger.



When pec minor gets (over-) used

The job of pec minor is to pull the shoulder forward, and in doing so pulls the shoulder blade forward and down.

Think about how often you have your arms in front of you:

  • Working at the computer
  • Driving
  • Texting
  • Cycling
  • Cooking
  • Massaging clients!

the list is pretty endless. We spend a lot of our days with our arms out in front of us - especially the arm on our dominant side (so the right arm if you're right-handed).

As you can see from the diagram, the muscle fibres are bundled into 3 big trunks of muscle fibres, and each of those trunks attaches to the front of the shoulder at a bony prominence called the coracoid process. The 3 bundles of fibres then run separately down to the 3rd, 4th and 5th rib.

When the muscles contract they pull on the coracoid process and pull the whole shoulder joint forward and down.

The thing is, each of those bundles of fibres is actually quite short. When they become "set" because of the habit of having your arms in front of you, they're really hard to stretch out.


The trouble with pec minor

There's an obvious visible problem with pec minor becoming shortened (i.e. "set" through overuse) - and that's that a person can become round-shouldered.

But there's a more painful aspect to a shortened pec minor, too:

Given that the function of pec minor is to pull the shoulder blade down and forward, if pec minor is always tight then the shoulder blades are always pulled apart further than they should be.

So the shoulder blades (called the scapulae) are stretched out away from the spine, lengthening and weakening the rhomboid muscles that run between the spine and the edge of each scapula.

This can lead to constant ache in the shoulder between the shoulder blade and the spine. It's an example of the villain and victim principle - here the pec minor at the front of the body is the villain, but the pain is at the back of the body in the rhomboids.

Treatment of an ache at the top of the back is often focussed incorrectly on "relaxing" the rhomboid muscles at the back, when they're already lengthened out too much - instead, it's the villainous pec minor that needs to be sorted.

And here's the real trouble with pec minor: because the fibres are fairly short and become set easily treatment is "vigorous" - er, that's a euphemism for painful.

Of course, you can help yourself with good stretches: move your arm backwards, outwards and slightly up - holding on to a door frame behind you, and do a very gentle pull for one minute. Again, because we've usually had a lifetime of having our arms out in front of us, it's going to take a good few months of stretching like this a few times a week to have any effect.

Remember, too, that the shortened pec minor will have lengthened rhomboids at the back, so those will need to be strengthened with exercises over the same period. But that's a subject for another day.

As ever, if you think I can help, give me a call.