“Henneman’s size principle” and it provides the basis for why Myo Reps work so well.Evolution is an effective optimizer. If you are wasting energy, you’re dead. That sounds harsh in the modern, comfortable world, but it’s true, and a large part of how our muscles contract. The brain — via the central nervous system — will only contract as few muscles as it takes to get the job done. If you are walking down the street at a moderate pace, only your weakest muscle fibers will activate, not your strongest ones.