- Set a bench to a flat position.
- Sit and grasp a dumbbell in each hand, resting each atop its respective knee.
- Slowly lie backward onto the bench, while concurrently moving the dumbbells from your knees to a supported position at your sides, and then press them up--while concurrently turning them so that your thumbs are facing one another--until your arms are nearly extended. This is the starting position.
- Slowly lower the dumbbells downward by bending at your elbows until your arms are parallel with the ground (horizontal), inhaling throughout the movement.
- Press the dumbbells upward until they nearly meet at the top (above your chest), exhaling throughout the movement. When in the fully extended, "pressed" position, you may briefly isometrically contract your pectorals to hit the sternocostal head (i.e. inner aspect).
- Repeat steps 4-5 for as many repetitions as are desired.
Dumbbell bench presses primarily work the pectoralis major and pectoralis minor muscles. In addition, the triceps brachii, anterior deltoids, clavicular head of the the pectoralis major, serratus, coracobrachialis of the biceps, and anconeus of the forearms are worked.
As noted above, when your arms are in the fully extended, "pressed" position (above your chest), you may isometrically contract your pectorals to better recruit your inner chest (i.e. sternalcostal head).
Isometric contraction of muscles is performed in a static (non-moving) position, as opposed to moving through a range of motion. In other words, when contracting your muscle(s) isometrically, both the muscle length and the joint angle will remain unchanged (i.e. are actively held in a fixed position) throughout the contraction of the muscle.
As with any pressing motion, your elbows are susceptible to injury. The best way to avoid injury, as always, is proper form. Remember to not "lock out" your elbows in the extended position, especially if you believe you are susceptible to such injuries. This means that before you press to the point where you cannot press any further, stop - that is, keep an ever-so-slight bend in your elbow at the top point (full extension) of the movement. This won't be a concern for everybody because as was discussed earlier, everybody's anatomy is unique in make up. So, if you aren't experienced enough to determine if this motion is a possible point of injury, just don't do it. Refraining from complete flexion by just a fraction will not detract from you training or overall strength and may very well prevent an unnecessary and possibly long-lasting injury.
A false grip - that is, a grip where the thumbs are not wrapped around the bar - can provide additional power and enable more weight to be lifted. However, a potential consequence of using this grip could be injury. If the hands are sweaty or form falters the weight may fall at the peril of you or others. Many claim that it is more comfortable to hold the bar in this manner, but for most a false grip begs for wrist hyperextension and falling weight injuries. Unless you are a professional, a false grip should prove unnecessary.