The plank is used as a core exercise. It’s a nice way of training the abdominals to prevent lumbar extension. Ala don’t do this:
I actually also like to use the plank as a shoulder mobility exercise. Let me explain.
Without going into too much detail, two common issues for those with shoulder pain / movement issues are:
1) Lack of posterior / inferior glide of the humerus i.e. the humerus glides too far forward.
For more on this check out: Best exercises for the subscapularis.
2) In conjunction with 1), the internal rotators of the humerus are often excessively dominant / tight / active / whatever you want to call it.
For more on this see the above link and or 3 common tight muscles.
By adjusting the arm positioning during the plank we can actually work on correcting these 2 issues. First, the common arm positioning during a plank:
Notice a few things:
-The arms are internally rotated, giving into those tight internal rotators just discussed.
-The forearms are pronated (palms are down), which gives into the shoulder internal rotation. This can also cause issues at the elbow. See What causes Tennis Elbow? for more.
-The elbows are below the shoulders. In the below picture I’m referencing the horizontal plane, not vertical. (Yes, they are below in the vertical as well, but that’s not what we’re discussing here.) Thus, our “opposite reaction” is in favor of superior and anterior glide of the humerus. We do not want this.
Turning the plank into a corrective shoulder exercise
Adjusting the arm positioning we can do this:
Now the shoulders are in neutral, if not a bit of external rotation:
The forearms in supination (palms are up):
Looking at things from the side:
We also have the ground, which is opposing gravity, giving a nice posterior and inferior glide on the humerus. We’re now using the plank exercise as another method of loosening up the posterior capsule. Something nearly everyone could use more of:
This isn’t some magical way of loosening up the shoulders. However, every – single – movement / exercise is an opportunity to correct movement impairments. By adjusting our planks like so we continue to tip the amount of “better” reps in our favor. The more we can do to correct a movement impairment, especially when we’re going to be doing the exercise anyways, the better our chances of alleviating pain and impairments.
If you’re someone with really tight shoulders you’ll even notice your arms reactively internally rotating while you do your plank. You’ll actually have to actively resist this motion. Further indication of how tight you really are.
For most people doing the exercise in this fashion is more work too. The abdominals will work even harder.
It’s all about Technique, technique, technique.