What event post world war ii resulted in significant changes in exercise science in regards to fitness?

When World War II was over it came to light that the military had rejected over half of the men who were drafted or had given them lighter duties, because they were not fit enough for combat. The United States began to realize it needed to focus more on fitness. A researcher by the name of Thomas K. Cureton began to study exercise and fitness. He conducted many experiments and was able to establish a set of guidelines for maintaining fitness.