1. lie on a decline bench and take a shoulder-width overhand grip on the bar.
2. Lower the weight slowly down to touch your lower chest.
3. Push the bar straight up until your elbows lock out.
Primary: Lower pectoralis major (sternal head). Secondary: Triceps, anterior deltoid.
Trajectory: The decline angle determines trajectory. As the bench is tilted head-down and the decline gets steeper, the focus shifts progressively lower down the pectoral muscle. The lower pectoral is best targeted at a decline of 20 to 40 degrees to the floor. Steeper declines shift the focus from the chest to the triceps. Flare your elbows out as the bar is lowered to maximize pectoral isolation.
Increased decline shifts focus to lower down the pectoral muscle.
Hand spacing: The ideal hand spacing is shoulder width. Wider grips target the outer section of the muscle, afford a greater stretch, and minimize triceps contribution. A narrow (close) grip targets the inner pectorals and requires more work from the triceps.
Range of motion: A shorter rep terminating the press just before lockout keeps tension on the pectorals and reduces the amount of triceps assistance.