To do a chest fly, lie down on a bench with your feet flat on the floor. During the exercise, your head, shoulders and butt should always be in contact with the bench or the floor. Begin by picking up a pair of dumbbells, one in each hand, and holding them above your chest with straight arms, palms facing inward. Slightly bend both elbows and inhale while you lower the dumbbells to shoulder height in an arc motion. Exhale and slowly bring the dumbbells back up to start.

Keeping a slight bend in both elbows throughout the entire chest fly exercise is important for safety. Never lock your arms, and never let your wrists twist or drop. During the lowering portion of the exercise, don’t drop the weights any lower than shoulder height; doing so could put too much pressure on your joints. Using dumbbells that are too heavy is also risky for your wrist and shoulder joints. Start light, and take it up as you feel ready.

“Los Angeles Times” health columnist Karen Voight recommends slowing the chest fly down to avoid “cheating” by using momentum to complete the movements. As you lower the weights, count to four. Do the same as you raise them back overhead. Tracy Anderson, author of “Movement Science for Personal Trainers,” urges anyone practicing the chest fly to think of three things during the upward motion: keeping shoulders down, elevating the ribcage and squeezing the chest muscles.

You can target either your upper or lower chest by changing the angle of the bench you use for the exercise. When the bench is at an incline of 20 to 30 degrees, you’ll emphasize your upper chest muscles; a decline of the same angle emphasizes the lower chest. If you aren’t at a gym or have no bench to work on, you can do the chest fly on the floor. Lie down and bend your knees so that your feet are flat against the floor. Bring the weights down to your shoulders at the floor and slowly lift them back up.