1. The feet become thicker and softer.
2. The skin, muscles, bones, and tendons have become more resistant to injury.
3. The skin becomes tough and pliable so it can shape around objects.
4. Running attentively helps to avoid hazards.
5. Form flaws are corrected.
6. There is more work in barefoot running, especially when the surface is not super smooth.
7. Muscles and tendons feel discomfort, joints do not.
8. A little soreness is a training effect as tissues get stronger.
9. Running is mostly elastic recoil.
10. The small but essential springs are the intrinsic foot muscles; the large springs stabilize the foot and recoils one off the ground.