The brachialis muscle is the main flexor of your elbow joint. If it harbours active trigger points, it can trigger pain at the base of your thumb, in your elbow or at the front of your shoulder.
As it is covered by the biceps brachii, this muscle is not known to many people. People who frequently overload it include fitness enthusiasts, guitar players or rock climbers. Still, anyone can experience trouble in this muscle.
When this muscle is too tense, or harbours trigger or tender points, it can impair the extension of your elbow. Furthermore, lifting or holding heavy objects with your arm in a flexed position may be painful. Of course, any pulling motion can be impaired or painful too.
Such activities may be
The brachialis muscle gets overloaded and develops trigger points mainly through repetitive stress and overuse. That means if you use the muscle too often or too hard, it may give you pain.
When performing biceps curls, wielding a heavy chainsaw, or lifting furniture, take frequent rests, especially if you are not used to that kind of work.
It is really sustained stress which is problematic: The furniture-moving example being exemplary: You may over-stress the muscle because mostly you carry things with your elbows bent, which activates the muscle permanently.
Although this muscle lies deep to the biceps brachii, it is pretty accessible as the biceps can be pushed to the side quite easily.
Put your thumb in your elbow crease and move it a couple of times sideways. You should feel a muscle “jumping” under your thumb.
Travel a little upwards your arm to feel where the muscle runs. That muscle is your brachialis.
For massage, I recommend using the thumb technique.