The Bench Press and the Shoulder: What does my AC joint have to do with it?
Building up your pectoral muscles through the classic bench press is one of the most basic exercises in any strengthening program. This exercise is very effective in building up the pectoralis major muscle, as well as accessory muscles such as your deltoid and triceps.
This exercise does require your shoulder joint to be placed in a rather provocative position. This can place excessive stress on surrounding joints about the shoulder girdle if not performed correctly.
Lets start off with a little basic anatomy and then bring to light a potential problem and how to try to avoid it.
The boney anatomy of the shoulder girdle is made up of 3 joints: the acromioclavicular (AC) joint, the sternoclavicular (SC) joint, and the glenohumeral joint (the main shoulder joint).
The AC joint deserves particular mention when talking about the bench press. This joint connects the acromion of the scapula (shoulder blade) to the clavicle (collar bone). This joint experiences stress when the arm is brought across the body in front of you, like in the bench press.
This joint can experience an abnormal increase in these stresses when someone does a bench press with a bar, as opposed to free dumbbells, particularly with a narrow grip.
When someone uses the bar during a bench press, the arms stay in the same plane throughout the range of motion. If the grip is narrow then the AC joint will get compressed and stressed at the top of the press. This jams the clavicle into the acromion. Using free dumbbells will allow the arm to change position throughout the motion and limit AC joint stress.
This may not be an issue for most athletes, however some people will develop pain at the top of their shoulder over the years, or after an abnormal increase in activity.
One potential problem is distal clavicle osteolysis. This is a common problem that we see in weight lifters, which causes degeneration of the end of the clavicle. This can usually be treated with rest and activity modification, but sometimes it requires surgery.
Worst-case scenario, someone can develop arthritis in the AC joint over many years of poor technique and excessive lifting. We have surgeries to help this as well, however it is best to try to prevent the development all together.
The bottom line is if you experience any pain in the AC joint during a bench press with a bar, try using dumbbells instead. If this is still a problem then a period of rest from these particular exercises is usually best.
The goal of working out is to keep you healthy and strong over the course of your life. Modifying workouts if you are having pain can help you in the long run.