This muscle is a triangle shape muscle that sits on top of your shoulder blade and inserts on the top of the arm. Infraspinatus externally rotates the shoulder joint. Helps with shoulder extension and stabilisation. It is apart of the rotator cuff muscle and is prone to tendinitis.
What is the weakness of infraspinatus?
Working at a desk or in a bent over position or arms over your head can develop infraspinatus tendinosis. It can start with impaired movement such as not being able to reach back to pull on your seatbelt. Or even putting your arm behind you to put on your coat.
Sports can also irritate this muscle, rock climbing, handball, rowing, softball, some yoga poses (down and upward dog) and throwing balls.
Ever wonder why frozen shoulder takes longer to heal? It is because so many muscles are involved, the infraspinatus experiences this. Frozen shoulder is a condition that results in stiffness and weakness of the shoulder, adhesions and scar tissue that are located in the shoulder joint is a main cause.