It's located on your upper ribs, just on the side of your chest
Serratus anterior
The strongest protractor of the scapula is the serratus anterior muscle. It originates from the upper ribs and inserts along the medial border of the scapula. Contraction of the serratus anterior muscle pulls the scapula forward around the rib cage.
lower trapezius, serratus anterior
The serratus anterior muscle in humans and the serratus ventralis muscle in cats are functionally equivalent but have different names due to anatomical differences and the naming conventions in comparative anatomy. The term "serratus" refers to the serrated or saw-like appearance of the muscle, while "anterior" and "ventralis" indicate their positions in the respective species.
The serratus anterior muscle is located on the side of the chest and helps to stabilize the shoulder blade and move the arm away from the body. The obliques muscles are located on the sides of the abdomen and help with twisting and bending movements of the trunk.
Serratus Anterior
Serratus anterior and trapezius
anterior deltoid pectoralis major serratus anterior
The Serratus Anterior - this muscle is abducts the scapula and is commonly emploed in pushing movements - like punching. As boxers punch alot these muscles are very well developed
Rotators
yes
The main antagonists of the rhomboid muscles are the serratus anterior and pectoralis minor. These muscles work in opposition to the rhomboids to perform movements like protraction and downward rotation of the scapula. Strengthening these antagonist muscles can help maintain shoulder stability and balance in the upper body.