Parallel bar dips can be performed in a couple of different ways to target the chest, shoulder and tricep muscles. To emphasize working more of the chest muscles, the outer portion more specifically, this exercise can be performed with bars set wider (up to about 1 ½ times shoulder width apart) to a position that is comfortable to work in. The lower portions of the chest, as well as the front of the shoulders and ticeps can be more heavily worked when setting bars to spacing of your shoulder width or less.
A parallel dip bar frame can be found in most gyms and is simply a set of two round bars parallel with the ground and usually about four feet off the ground. Once you have decided the spacing of the bars and have set your hands in place, you will basically step or jump up to where you are supporting yourself above the bars. Here your elbows will remain slightly bent (not locked out) in the upward position. You will then lower your body to the point that is comfortable (yet forcing the muscles to work) for your arms and chest and push yourself upward. When you are at the peak of the movement, as previously mentioned, you will keep your arms slightly bent to avoid placing additional stress on your elbow joints. Performing the downward and upward position of the movement will consist of a single repetition. You will repeat these as desired to get the full amount of repetitions to challenge yourself.
Performing the movement more slowly and you will intensify the work on your chest muscles. To further challenge yourself you can also perform sets of this exercise with higher repetitions or add weight. Weight can most easily be added by wearing around your waist a special belt with a hook to place on it a dumbbell that is worn during the movement; belts like these can be purchased or if available borrowed at a gym. This movement is challenging and if you are looking to work up to it, many fitness gyms have available machines that allow you to perform parallel bar dips and take off some of your bodyweight to make the movement easier as you build up strength.
It is wise check with a physician to see that you have an acceptable level of health before beginning an exercise program. Further, it is wise to work with a personal trainer to learn the proper techniques for performing exercise movements. Always use caution when performing any exercise movement and slowly ease into performing exercise movements you are unfamiliar with.
REFERENCE / RESOURCE:
Kennedy, Robert. (1998). Basic Routines for Massive Muscles. New York, NY: Sterling Publishing Company.