Technique

The technique for both exercises is the same. Lie face up on a bench with your feet flat on the floor. If your back arches when you put your feet on the floor, place a step at the end of the bench and set your feet on this. Hold the weights with a grip just outside your shoulders. Press the weights above your chest, until your arms are fully extended, but do not lock your elbows. Pause for a count before slowly lowering the weights back down to your chest.

Muscles Worked

For either bench press exercise, pulling your elbows in close to your sides transfers the load to the triceps and away from the chest. With dumbbells, you can perform the exercise unilaterally -- holding only one dumbbell at a time. This version of the bench press activates the lower back and abdominal muscles more than the barbell bench press.

Range of Motion

Dumbbells provide an increased range of motion over a barbell. At the top of the movement you can bring the dumbbells together until they almost touch. Twist your hands so your palms face each other at the top to increase the range of motion even more. With a barbell, you cannot lower the barbell past the point where it makes contact with your chest, but with dumbbells you can continue to lower past this point, bringing the dumbbells to the sides of your body. However, this increased range of motion at the bottom of the movement may increase your risk of injury, as it places your shoulders in an excessively stretched position under a heavy load.

Weights

You can press more weight using a barbell than a dumbbell. A 2011 study published in the "Journal of Sports Sciences" found that the one-repetition maximum for the dumbbell chest press was 17 percent less than the one-repetition maximum for the barbell chest press. With a barbell, you can load the bar on a rack. Large dumbbells are unwieldy and require a spotter to put them in place to begin the exercise.