Trainees choose dumbbell bench presses for two main reasons: 1) The dumbbells allow variation in hand position, and that can make the shoulder feel more comfortable; 2) using dumbbells lets them reach parts of the pec that the barbell doesn't'and there may be some degree of truth in that.
The bench press targets the pectoralis major, the delts and the triceps, as well as the serratus anterior, a key shoulder muscle that runs from the inner border of the scapula to the ribs. The shoulder capsule, which is made of ligaments (ligaments attach bone to bone), can be overstretched. Two movements that naturally cause a forward motion of the shoulder are a throwing motion and a bench press or pushup motion. The forward movement of the ball (head of humerus) in the shoulder socket (glenoid fossa) can stretch the capsule or tear the cartilage ring around the socket (glenoid labrum). That can lead to shoulder instability because the ball is moving too much in the forward and downward position.
Some trainees turn to the dumbbell bench press because of the pain that the barbell bench press causes. They claim that turning the dumbbells in slightly can reduce or relieve shoulder pain. They also claim that they feel the dumbbell bench press differently. If you rotate the dumbbells so your palms face each other, you can lower them farther than you could if the dumbbells were in line, as in a barbell bench press. That causes more pec and delt stretch, and you can feel the exercise even more.
If you have an unstable shoulder, though, the dumbbell bench press may increase shoulder pain and worsen the feeling of excessive movement in the shoulder. So don't think dumbbell bench presses automatically let you work around the problem. They may contribute to it.
If you've had surgery to either reconstruct your shoulder ligaments or repair a significant tear of the glenoid labrum (usually a SLAP tear or a Bankart lesion), then the dumbbell bench press will likely allow too much stretch and may ruin the surgical repair. That's more common than you may think. I've seen personal trainers as well as strength coaches cause it to happen. The intention is make each arm work independently and have a full range of motion; however, the extra stretch that the dumbbell bench presses allow may be too much for postsurgical-repair patients. Something else to consider is that trainees are often injured when trying to get heavy dumbbells in position. Dan Howard, manager of Gold's Gym, Venice, in the 1970s, said he saw many bodybuilders tear a biceps tendon trying to put down heavy dumbbells after a set. I came across a product that helps avoid that risk: Power Hooks. They hang on a barbell bar, and the S curve lets you strap the dumbbells to them. You can hang your dumbbells on a bench press bar and then position yourself on the bench and lift them off their perch for safer presses. You'll find Power Hooks at powerhooks.com or at Home Gym Warehouse (www.home-gym.com or 1-800-447-0008).
Editor's note: Visit www.softtissuecenter.com for reprints of Horrigan's past Sportsmedicine columns that have appeared in IRON MAN. You can order the book, Strength, Conditioning and Injury Prevention for Hockey by Joseph Horrigan, D.C., and E.J. 'Doc' Kreis, D.A., from Home Gym Warehouse, 1-800-447-0008 or at www.home-gym.com.