For many bodybuilders and other strength athletes the weak spot in the shoulder joint is the external rotator cuff: small muscles to the rear of the shoulder joint which stabilise the joint during intensive exercises. If you want to strengthen these muscle groups and keep your shoulder joint free of injury, it's worth taking a look at the interesting results of a study that sports scientists at the American Sports Medicine Institute published in 2004.
StudyThe researchers attached electrodes to the shoulder muscles of 10 subjects so they could measure how hard the muscles had to work. They then got the subjects to perform 7 exercises that strength athletes do to make their shoulder joint more stable.
External rotatorsThe muscle groups that are most interesting are shown below: the teres minor, the infraspinatus and the supraspinatus. All three together make up the external rotator cuff.
ResultsThe side-lying external rotation turned out to be the most effective exercise for the teres minor, as the figure below shows.
The side-lying external rotation exercise is shown in the photo below right.
On the left above you can see the prone horizontal abduction at 100 degrees with full external rotation. The name's a bit of a mouthful, but in this case it's justified. According to the figure below, it's the most effective exercise for the supraspinatus.
Regular readers of this free webazine will already know that this exercise – aka prone full can – is a really good one for strengthening the supraspinatus. A study we wrote about a month ago came to the same conclusion.
For the infraspinatus, the side-lying external rotation turned out to be the most effective, as the figure below shows.