I created this exercise called the “Mermaid Slides*” because so many students in my yoga and Pilates Deconstructed® classes struggle to keep the head of their humerus centrated in the glenoid fossa in side plank. It’s often because the external rotator cuff muscles aren’t strong enough to prevent anterior translation at the glenohumeral joint (the shoulder rounding forward).
Most people (including yours truly) don’t strengthen the infraspinatus and teres minor muscles until it’s too late, meaning until after they get injured. This exercise will not only strengthen these muscles, but it also serves as a fun and playful regression for the side plank. Furthermore, it’s a great way to assess your dynamic “pulling power” in the coronal/frontal plane with less load than you would have in a full side plank.
The exercise is pretty easy to do with the palm facing down (forearm pronation) and the front of your shoulder rolling forward into internal rotation, but can you do it with the palm facing UP (forearm supination) with your shoulder in external rotation?
If you can, then try loading your shoulder in a kneeling forearm side plank (without any anterior translation at the shoulder joint) and practice the isometric pulling action of adduction and external rotation you employed dynamically in the Mermaid Slides.
Once this manageable, try a kneeling side plank on your hand as your next progression. Practice that version of the side plank for a while, and if you are able to keep the humerus centrated in the glenoid fossa, then experiment with the next progression: a full side plank on your hand with a split stance (bottom leg forward and top leg back). This variation is a great way to encourage the lateral hip stabilizers of the bottom hip and hip adductors of the top hip help out your shoulder by utilizing a wider base of support.
If your shoulder can stay stable and centrated with the split stance, then try the next progression of side plank with the ankles stacked.
Once you’ve given your Mermaid on the reformer some pulling and sliding power on the mat, send me your questions and comments. I would love to hear from you, or even better, watch YOUR “Mermaid Slide” video innovations!
*Sidenote: I have one client with whom we do a TON of external rotator cuff strengthening so she decided to name this area of the body the “back-pit.” If you are not fond of mermaids, no worries! You can call this exercise “Back-Pit Power Slides.”
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If you would like to study with Trina live or online, go to her website www.trinaaltman.com for her schedule of classes, workshops, immersions and trainings.