(aka Limb Length Discrepancy)
A functional shortage means one of your legs "functions" like a short leg. This is not ananatomical shortage where one leg is physically shorter than the other. This is acquired over a lifetime of walking. It begins with the fact that while both of your feet look identical, they do not work exactly alike. Almost from your first foot steps your body starts to identify this difference in pattern and begins to adjust your hips in order to compensate for this discrepancy in foot function.This adjustment takes the form of a rotation at the hip level (specifically the ileum bone) most commonly on the same side as your dominant hand. What this means to you is that the muscles which attach from the lower end of the spine to the hip are working "unevenly" in their strength, which additionally puts a "tweak" into the lower end of the spine. The result is low back/hip or buttock pain (seen as ITB and piriformis syndrome)
Statistically, approximately 85% of the world's population will exhibit this condition. As many as 2/3 are affected by pain.
If you have ever had your hips adjusted by a chiropractor (DC) or osteopath (DO), you may recall being told that "you have a short leg". Normally no differentiation between functional or anatomical difference is made. After the adjustment you would be told "you're straight or even again"
While most of those docs will discuss the difference with you, the problem here is that you walk away from the table right back into this instability and are back on the table within a week to a month,
and that's normal. If you do not have any pain or problem in this area, you are still vulnerable to it happening sooner or later. Conditioning and stretching will definitely
help. The real answer is to address the underlying condition of foot mechanics.
A precise fitting orthotic will improve foot and spinal alignment, body balance, restore truer "muscle and tendon tracking"
reversing inflammation, all by improving your bio- mechanics. Eventually
problems get better, you can get back to training with improved efficiency and
ultimately enhancing your performance. If you do see a chiropractor, your orthotics will "hold" the adjustments longer.
Functional Shortage Test (FS)
To determine if you have a "functional shortage" it is best to use a partner to be your eyes. If not,stand in front of a mirror, relax, close your eyes, jump up and down from foot to foot and shake yourself out. Open your eyes and look at your shoulder level. Can you determine that one shoulder is lower than the other? (If you know you have scoliosis, curvature of the spine, you cannot do this test) Next, step back from the mirror and place your thumbs extended, parallel to your belt on the bony points in front of your hips. You need to be back far enough to see this. Can you tell if one thumb is lower than the other? If you can tell that the shoulder and hip that are lower are on the same side, this is a good indication of a "FS". Are you dominant handed on that same side? If so this is most probably a case of "FS" (if you are ambidextrous you might feel the other side is your dominant hand).Be aware there are more scientific ways to determine a true functional shortage. This is a "down and dirty" way of doing it, but fairly accurate if you've done it right.