People use the term "fitness," but few people if anyone really understands the concept well enough to define it in a way that all can agree upon.
Fitness is composed of five separate components (also referred to as "abilities"): muscular strength, muscular endurance, cardio, neuro, and flexibility. Athletes develop and combine these components in order to best perform their specific skill set(s.) Some athletes may require fantastic flexibility while others require great muscular endurance, but there is no way to compare one ability against another.
Overall fitness is not just the sum of these parts, but is affected by the mindset, heart, intelligence, drive, determination, and spirit of the individual athlete.
Therefore, to call Michael Phelps, or anyone else for that matter, "the all-time fittest man" is unclear, and leaves a lot to be desired.
Almost any of the men on the top 50 list could have been arguably the all-time fittest man. Heck, there have even been a few Eastern-bloc female athletes that might have made the list.
How did Al Oerter get left off the list?
Where are the gymnasts, and the springboard divers?
We can all appreciate how truly inspirational our greatest athletes have been, but there is no way to compare athletes from different sports. We don't know whether pitchers are better athletes than hitters or fielders, but we know we can't compare one against the other. "The Greatest," "The Myth," "The Man," "Sweetness," "Magic," "Charlie Hustle," "The Great One," "Mr. October," "The Golden Bear," "The Real Deal," "The Mailman," "The Worm," "His Airness," and many others could vie for the title.
There are, however, two more factors worthy of considerations for this discussion: longevity, and drug scandals.
Many of our top performers have had relatively short careers, while others have had careers that spanned three, four, and even five decades. How do we compare "Mr Hockey," with his record-setting 40+ NHL career, to that of The Baltimore Bullet?
No can do.
Do we even want to try to compare the drug-enhanced performance phenoms to the clean and natural athletes who are out there paying the price for their fitness?
I don't think so.
Michael Phelps has shown us some amazing performances in the swimming pool, as did Mark Spitz and Greg Louganis before him. His skill level is top notch, his talent unquestionable, his drive and determination superior, and his training routines must be intense.
The question is, do I consider Michael Phelps the fittest man of all time?
I have to agree with Sebastian Coe, director of the 2012 Games and no slouch himself when it comes to fitness records, when he says that he doesn't think Phelps is the greatest.
I still remember when Michael got caught doing drugs shortly after the 2008 Games. I know that in 2012 he placed fourth in an Olympic final. Fourth!
Essentially, we're talking about a man with an eight-year career, who has competed spectacularly well in three Olympic Games and took only a fifth place in his first Games. Maybe, just maybe, after another 50 years, when he's 78, I'd consider him for the honor, if he can show me a lifetime of astonishing fitness achievements, across a broad variety of sports and skills. Until then, Walt Stack, Johnny Weissmuller, Al Oerter, Dean Karnazes, Carl Lewis and many others have all showed me more, for far longer than Michael Phelps, brilliant as he has been.