I see Athletic as being nimble and in real good shape. Floyd Mayweather is Athletic , Cotto is not. Hes a bit too bulky his movement are not as fluid. Fast i see as Footwork like a prime Manny Pacquiao, the step inside was so fast he was laying into his opponant before they could react, or a lightening jab. Joe Calzaghe punches fast, Carl Froch punches slow.
Speed is just one attribute to describe someone who is athletic. Someone who is athletic is more than just fast. They have good agility, dexterity, coordination and are often explosively quick as well.
They're not exactly interchangeable. Athleticism includes but isn't limited to speed. Agility, fast-twitch muscle acuity, natural "gracefulness", etc.
Yeah. I've always maintained that Usain Bolt is a poor athlete, he's just outrageously fast. Guys like Yohan Blake are far better athletes.
In NBA terms: Leandro Barbosa is FAST. LeBron James is a complete, well-rounded ATHLETE par excellence (and that doesn't even get into skill and "court vision", the equivalent of ring IQ)
I think Bolt would be an example of someone who's fast, and Ashton Eaton would be an example of someone who's athletic.
to me, being athletic just means that youre more in tune with those connections between what your mind wants to do, the specific instructions it sends to the body, and your bodies ability to receive those instructions and carry them out in the most efficient form possible. when youre athletic, your muscles, vision, balance, and the other senses, get highly coordinated with your minds instructions. that means you can learn almost any sport, much easier and much faster, than someone who is not as athletic. fast, is just one of the benefits of a finely tuned human body.