This is a wild theory. I was debating calling this post, "Why the long face?"
Please read this blog post from The Paleo Periodical or watch the video below. I know it sounds crazy but I think they are probably correct.
Here is my contribution. I'm 49 years old. Sometime in my forties I started losing muscle mass. As someone who did 5 to 10 hours a day of movement art from age 17-40 and now does about 3 hours a day, it is a shock. A shock which took effect slowly. I can still build muscle, it just takes more work and more time. But that is common and not very important.
What is important to understand is that if you are a professional mover, like a circus person, a dancer, a gymnast or a martial artist, you either figured out how to work with the muscle-tendon systems in your body by the age of 25 or you quit. What causes problems for professional movers are joint injuries. And joints are held together by ligaments, not muscles and tendons. The definition of a ligament is a piece soft tissue which transfers force from one bone to another. But people don't have much voluntary control over ligaments, they either do their job well or they don't. As ligaments get looser or stiffer (from use and age) the space inside the joints increases and that creates a kind of fragility--a potential for injuries.
Can muscles help reduce joint space? Maybe. But my own experiments tell me that the big muscle groups that people normally strengthen don't help much. They help some. I'm still solving this puzzle, but my preliminary results are interesting. What I've noticed is that I have lost muscle mass in some strange places, places that have a big systemic effect. For instance I've lost strength in the space between my pinky finger and the next finger. Squeezing those two fingers together really helps organize my shoulder. Or the space between my baby toe and the next one over, squeezing those together pulls my fibula in closer and brings tone around my sacrum.
So naturally when I watched the video below I started squeezing my jaw together. It really brings up tone in my lower back (as Chinese meridian theory would predict), it also brings up tone in my chest. Is anyone else doing experiments like these? I'd like to know what you have found.