Ultra-endurance was once thought to be harmful to human health, but now we realize that we have all these traits that are perfect for ultra-endurance: no body fur and a glut of sweat glands that keep us cool while running; narrow waists and long legs compared to our frames; large surface area of joints for shock absorption.
Ultra izdržljivost se nekad  smatrala štetnom za ljudsko zdravlje, ali sada shvaćamo da imamo sve te osobine koje su savršene za ultra izdržljivost: nemamo krzna i mnoštvo znojnih žlijezda koje nas hlade dok trčimo: uzak struk i duge noge  u usporedbi s našim okvirima; velike površine zglobova za apsorpciju udara.