1. While seated on the edge of a flat bench, grasp two dumbbells in an overhand grip.
2. Rest the dumbbells in an upright position on the edge of your knees.
3. Carefully lie on the flat bench, bringing the dumbbells to the sides of your torso at chest level. Make sure to bring the dumbbells up simultaneously. Feet should be planted firmly on the floor.
4. Slowly adjust the dumbbells with your arms fully extended at right angles to the floor. Press the weight up to the locked position. The dumbbells should be held directly over your chest area, slightly touching each other with palms facing inward.
5. Elbows must remain flexed throughout the entire movement.
6. Slowly lower your arms out to the side of your body with your arms at right angles. The dumbbells should be slowly lowered in an arc like motion toward the floor until your chest is comfortably stretched.
7. At the bottom position of the exercise your hands should be parallel the trunk of your body. Raise and repeat. The elbows should be slightly bent throughout the whole movement and should not be altered from start to finish (imagine your arms wrapping around a large tree).
The flat bench dumbbell fly is a great isolation exercise for the chest. This exercise is meant to stimulate the entire region of the chest and to pump blood into the area.
Personally, I enjoy doing flat bench flyes at the end of my chest workout. This way, I ensure that my chest is entirely exhausted before I head to the showers.
Although this exercise is considered an isolation exercise, it also hits the shoulders and triceps muscles. Although not to the extent that the bench press does, this exercise does work those secondary muscles.