Gestalt Education released a video interview with Thomas Michaud talking about the function of the muscles spindles during locomotion, and the energy storage characteristics of tendons during walking or running.
Tendons will stretch 10% during walking or running to help store energy to propel you forward. This makes you a very efficient walker. During leg swing, your biceps demotic will isometrically contract to lock in place, so when you heal strike, your tendons store the energy.
I counsel patients to do short foot exercises to strengthen their intrinsic foot muscles. But from this video I learned that muscle grow better if you strengthen them in a lengthened position. So to strengthen the intrinsic foot muscles, you have to start with the toes in extension.