The sternalis muscle is not existent in every human.
Approximately 5% of us have one.
The muscle can send pain from your chest bone area over to your shoulder and into your arm.
Beside the pains described above, which often “feel deep” or have the quality of a sore muscle, the muscle does not impair any movements.
There is no particular function that can be attributed to this muscle.
As there is no particular function of the muscle, there are no activities that are known to overwork the sternalis muscle.
But it is known that it may develop trigger points with acute angina pectoris or myocardial infarction.
A good way to massage this muscle is using a massage ball against a wall.