"Physical fitness is not only;y one of the most important keys to a healthy body, it is the basis of dynamic and creative intellectual activity. The relationship between the sounders of the body and the activitvities of the mind is subtle and complex. Much is not yet understood. But we do know what the Greeks knew; that intelligence and skill can only function at the peak of their capacity when the body is healthy and strong." 

President John F. Kennedy

What i am understanding is that most people think, once he said about physical fitness we all thought about wiegth or disease on over weight people. What he is trying to say is that in order to understand thing we need to be in shape and healthy. Being healthy makes us understand  more critical thinking and what choices to choose. Being physical healthy can help you comprehend things not a lot of people can. Being physical healthy may not help you be in shape put also have a healthy mind. Be mentally healthy.