Your leg that is up on the table is now in the position for a side split. Now do it with the other leg. Like the wheels on your Land Rover, your legs boast independent suspension. That means you should be able to bring the other leg out at the same angle and do a split without stretching a thing. The muscles tighten up and resist lengthening.
Russian scientists call it antagonist passive insufficiency.
Whenever you reach too far compared to this standard, the stretch reflex kicks in and reins your muscles in. A muscle with pre-Depression connective tissues and more scars than a prize fighter is still long enough to display as much flexibility as allowed by its associated joints. Master the muscular tension-and you will be as flexible as you want to be, at any age. If you compare your muscle to a telescopic antenna, conventional stretching mangles the outer tube in a vain attempt to elongate it. The reflexes form a hierarchy where some of them may override others because they have more 'stripes'.