Bench press is the main action to exercise and strengthen chest muscles. Bench press is a compound action, involving multiple joints, including shoulder joint and elbow joint.
The most commonly used equipment in the gym is flat bench press, and many people can push a lot of weight. The pectoral muscle only controls the movement of the shoulder joint and pulls the upper arm to the chest from both sides. The movement of elbow joint is completed by triceps brachii, which makes the arm change from bending to straightening.
Action process
Hold the barbell with both hands, wider than the shoulders, and buckle your thumb on your index finger. The appropriate grip distance should make the forearm basically perpendicular to the ground at the lowest point of action. Too narrow grip distance will lead to too much participation of triceps brachii, which will weaken the stimulation to chest muscles, while too wide grip distance can only exercise the outside of chest muscles.