How often, in real life, do we externally rotate our shoulders? To know what I mean by that, place your hands lightly on front of you, on a desk or shoulder.
Rotate your shoulders away from your ears, so that the elbow moves to outwards and the crease on the inner arm points upwards. You should feel your chest broadening.
This subtle but important action is known as an external rotation of the shoulders - a move that exercises muscles of the four small but important rotator cuff muscles and helps prevent common shoulder injuries.
Lack of use
The shoulder joint has the greatest mobility of all the body's joints. The downside is that it also has the least stability and is most likely to be dislocated.
The rotator cuff muscles guard and stabilize the joint, so keeping them strong is vital.
In our desk-bound Western lives, there is normally little need to exercise the rotator cuff muscles - especially the pair responsible for outward rotation.
These are called Teres Minor and Infraspinatus; the other two rotator cuff muscles are the Subscapularis and the Supraspinatus.
Enter yoga. A good yoga instructor frequently tells his or her students to take the shoulders away from the ears while in Downward Dog, rotating them outwards. There is good reason for this.
Many aspects of yoga can help us overcome deep-seated physical and psychological habits. This is just one more - our customary stance, whether it's at the computer, swimming or lifting weights, is to keep the shoulder muscles internally bound.
In the long term, this weakens the rotator cuff muscles - the four small muscles surrounding the key 'ball and socket' joint of the shoulder.
In the worst case scenario, lack of usage means the cuff muscles become weak or injured and can no longer perform the crucial centering function of supporting the ball and socket joint.
So what can you do to keep your rotator muscles - and therefore shoulders - strong and flexible? Several key postures can help.
* Downward Dog (Ardho Mukha Svanasa). Listen to your teacher when he or she instructs you to roll your shoulders away from your ears!
* The same action can be performed in asanas such as Warrior Two (Virabhadrasana II), Upward Facing Dog (Urdhva Mukja Svanasana) and in Four-Limbed Staff Pose (Chaturanga Dandasana).
* Plank pose can also be practised in this way - again, notice the chest expanding and lifting. Come down from Downward Dog.
Practising external rotation of the rotator cuff muscles helps to:
* Broaden and lift the chest.
* Open the space between the shoulder blades.
* Reverse our habitual tendency to keep the muscles turned inwards.
* Counter internal rotation-focused gym and sports exercises. Swimming, tennis and gym moves involved the pecs (such as press and pull-ups) can over-use the internal rotators.