" PHYSICAL FITNESS IS NOT ONLY ONE OF THE MOST IMPORTANT KEYS TO A HEALTHY BODY,IT IS THE BASIS OF DYNAMIC AND CREATIVE INTELLECTUAL ACTIVITY. THE  RELATIONSHIP BETWEEN THE SOUNDNESS OF THE BODY AND THE ACTIVITIES OS 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.
                                               BY PRESIDENT JOHN F. KENNEDY

 

What this quote means is that that not only been fit helps the body but also the mind. This means that you have to be in fitness but your mind also needs to be fit. Meaning that one with out the other don't work. So you need both fitness and intelligence. Without one of those two it affects the body. Also not every body and not every mind are the same. Some have less capacity of skill. But others have more intelligence. So they both have to work at the capacity that they have  depending on the person.With a intelligent mind you can know what is wrong to do and what is good. The intelligence can lead you to the right pass as long as you are wise in what you choose to do