Pec deck flys work the pectoralis major muscles (i.e. the main, large chest muscles), to include both the sternal head (i.e. inner aspect) and the clavicular head (i.e. primarily the upper aspect of the chest, but also the upper-outer aspect).
- Adjust the seat so that when the handles are grasped your upper arms are parallel with the ground, i.e. the angle of your elbow joints is 90 degrees. Note that once you are seated and in position, your arms should be open with your elbows out to the sides; if not contraindicated (by previous injury or pain), it is preferable that the handles are set in such a position that your chest receives a stretch when in the extended starting position (with your elbows out and back).
- Sit with your feet planted and grasp the handles (if handles are present). Your forearms should be pressed against the pads.
- Squeeze your arms together, exhaling throughout the movement. Once your arms meet in front of your face, you may isometrically contract your chest muscles to ensure that full inner chest muscular recruitment is achieved.
- Allow your arms to move apart and back, inhaling throughout the movement. Best outer chest muscular recruitment occurs when the weight pulls your arms all the way back, thus stretching your chest fully. Only allow such a stretch if it is comfortable to do so.
- Repeat steps 3-4 for as many repetitions as are desired