An overworked teres major muscle or one that contains trigger points can mimic shoulder bursitis or a thoracic outlet syndrome.
People that often suffer are athletes like gymnasts, rock climbers, baseball players or rowers.
Trigger points in muscles can make them painful right at their location and at other, seemingly unrelated parts of your body.
The main pain zone of the teres major is the back of the shoulder.
Besides that, pain can radiate to the front and side of the shoulder and down the backside of the arm.
The pictures below show how common it is to feel pain in the highlighted area.
The darker the red, the likelier it is to feel pain in the respective spot when the teres major muscle contains active trigger points.
If this muscle is overworked, all movements that require lifting the arm to the side and to the front may be impaired and/or painful.
Why? Because an overworked muscle usually is very tight and in a shortened position.
The movements mentioned above all include an elongation of the muscle as they display the opposite direction of the muscle functions.
On the other side pulling on things – pulling on a blind to open it – may be also painful because the muscle needs to contract.
Always remember: An overworked and tender muscle can give you trouble, no matter if you contract and thus “use” it, or if you stretch it.