There may well be subcellular problems that cause all kinds of bad-health, but not being well-mixed is not one of them.

Movement at the level of sports won't cause well-mixed cells - their fundamental frequencies are too different.

That would make people who ride older rail trains (like Chicago's trains) regularly super healthy. People who ride horses would be super healthy, too. Train conductors. Anyone who does a lot of off-roading. Etc. Oh actually, people who have shaky legs would have disproportionately healthier legs than the rest of their body.

But actually moving around a lot wouldn't make a difference if the bits in your cells are moving around at hundreds of miles per hour.

> but did we think of looking intra-cell?

Yes, a lot of science has "thought of" at looking intra-cell. In fact, the explanation of "don't shake their cells enough" must be very fringe because I haven't heard it any one time before from any serious scientist or a health book etc. The human body is much more complicated, and the way we understand many of the functions of it, including healthy functions, are based on biochemistry, both intra-cell and throughout the body.

Also "shaking the cells" can't even be that important physically, when you compare the speeds at which the limbs move during running to the base speeds of molecules inside the cell due to basic heat-based brownian motion.