The video demonstrated below, by an orthopedic surgeon, shows the mechanics of why shoulder impingement happens with the tendons.
See the small space between the ball acromium? That is where the impingement happens. Making sure the supraspinatus tendon, which pushes the ball down as the arm bone is lifted by the deltoid, is working well is a big part of the picture of shoulder healthy function. BUT….if you raise the shoulder blade UP by STRENGTHENING the muscles which lift it up, (such as serratus anterior) and STRETCH muscles which PULL it down (such as latissimus dorsi) you can gain more space, which puts less pressure and pinch on the supraspinatus tendon.
http://comstockpt.com/2011/11/22/neck-pain-stretches-out-olympia-wa/ This link will show you some latissimus stretches, and if you refer to Part 1 in this series of blog posts, with the man leaning against the wall you can see how to strengthen the serratus anterior
The serratus anterior muscle is THE core muscle of the shoulder and arm. It lifts and supports the shoulder blade and arm from below and underneath. This muscle is key to good posture.
During the day at work, school, and chores and sports, to remind the serratus anterior to contract and help you have good posture and reduce pain, here is a video:
If you are interested in research on the serratus anterior and shoulder pain, here is a link to an article: http://www.aott.org.tr/index.php/aott/article/view/4897/2610
Is your arm or pushup P90X workout difficult? Did you order your P90X to come to Olympia, Lacey or Tumwater, only to find out you are having problems? Are you struggling but not sure why? Do you have shoulder blade or middle back pain? You might have weak shoulder blade muscles that make your shoulder wobbly on your ribs. Here is what this looks like (the left side is the weak side) when you lift your arms up overhead :
Here is what it looks like when you try to do a push up:
Tune in the next few days to see a couple of exercises to fix this!