According to Merriam-Webster Dictionary, an athlete is "a person who is trained or skilled in exercises, sports, or games requiring physical strength, agility, or stamina." 

Wikipedia.com explains that "A superior athlete is one who has above average physical skills (strength, agility, and endurance) and is thus more suited for physical competition.

Olympians are athletes who compete at Olympic games, regardless if they win a medal or don’t. Being eligible to participate in that renowned event means that they have displayed outstanding athletic abilities and achieved excellent results in their respective sports. It is not an easy thing to accomplish, which is why every athlete that reaches the Olympic team deserves the utmost respect. However, being an Olympian also means respecting core values even outside of the sports fields.

Competitors in many sports like to think that their sport is the hardest to do, the most physically demanding. There are many lists of the fittest sports, with boxing and gymnastics commonly on top.

Motocross riders are rarely considered, but should be.

I love all motorsports and I love team sports as well, but motocross is a cut above. I'm convinced that it is the most challenging sport on the planet, and it comes with dire consequences when you fail. It's a motorsport, but it's much more about the rider than the motor. It requires incredible skill. It's almost always necessary to start the sport just after you begin walking, and you have to ride several times a week for about 15 years to get good enough to ride at a professional level.

Motocross is also a mental game. You need to be smart and have your emotions well in check to be successful in motocross. In motocross, yahoos tend to end up on the ground—or worse, in wheelchairs. Every time a motocross racer takes to the track there are butterflies in his or her stomach. Every motocrosser knows it can all go wrong in a heartbeat. This adds to the intensity of the racing battles—and there's not only competition between riders, but also battles between each rider and the track itself.

Physically demanding
Studies consistently rank motocross among the most physically demanding sports in the world. During a typical race day, a pro motocrosser wrestles with a 200-plus-pound bike for 30 or more minutes in each of two motos. Take my word for it, you cannot let up for even an instant. It requires both phenomenal aerobic and anaerobic fitness as well as incredible mental focus. You are holding on and bracing yourself under braking, when you accelerate (motocross bikes have the highest power-to-weight ratio of any production vehicle) and throughout every moment in between. Motocross bikes often seem to have a mind of their own and they are constantly trying to get away from you. Add to these demands the constant, unforgiving impacts of landing off large jumps. Even with modern suspension you definitely feel it when you fall out of the sky from heights equivalent to a four-story building.

Broken ankles and wrists caused by landing impact are common. The danger factor adds to the already astronomical physical demands. There are not a lot of fatalities, but the surgical pin industry could be completely supported by the compound fractures suffered in motocross. When you break a bone in motocross it's rarely a clean break and you tend to continue rolling, tumbling, and generally flopping about long after the point where the bone fractures—and the bike is always lurking about somewhere looking for an opportunity to crush you in the process.

Poetry in motion
Putting all of the manly, tough-guy stuff aside, motocross is a beautiful ballet of man and machine, when it's going right. There's no sport that even comes close to the beauty of a bike skipping across deep whoops, floating high in the sky or riding the back wheel down a rough straight—which brings me to another distinction between motocross and other motorsports.

Man over machine
Motocross is more about the rider than the machine. I love the spectacle of Formula 1 racing, drag racing or even NASCAR, but in all of these sports the guy with the best vehicle tends to win. This is not the case in motocross. Of course all of the top riders have very well-prepared bikes, but there's little about them that you can't buy yourself, and if all of the top riders swapped bikes the same guy would still win. If you're good enough, you can pop into your local bike dealer, buy a bike and then go out and win a national championship.

This makes motocross an everyman motor sport. It certainly helps if you have a little spare cash, because motocross is not cheap. But you don't need $100,000 to race at even the highest levels. Depending on what age group you are talking about (big bikes cost more than little ones), you can get your kid into motocross for between $2,000 and $5,000. I recommend that you do.

A family sport
I loved racing motocross as a carefree youth, but I'm a father and family man now, which brings me to what I have come to regard as the greatest thing about motocross—it's a fantastic family sport. It's my son's turn to race now and my turn to stand back and watch him learn the joys of motocross for himself. In fact, the motocross community is like a tight-knit family in itself.

Each weekend we all drag our trailers out to one of the tracks on Vancouver Island and camp for the weekend. The kids run amok in various packs while the parents sit around the campfire, drinking beer and eating Cheezies. It's just like regular camping but better, because there's something really fun to do during the day.

Racing provides a lot of quality time with both my immediate family and my motocross family. Unlike most other motorsports, motocross is kid-friendly and it caters to the geriatric crowd as well. There are racing classes for kids as young as four and as old as 40 and beyond. It's not a cheap sport, but you can’t really put a dollar value on quality family time and keeping your kid happy, focused and away from juvenile trouble.

Research has provided some insight on the physiology of an MX athlete.  Physiological measures have indicated that even recreational MX riders have greater aerobic capacity and vertical jump height than population norms (Burr, Jamnik, & Gledhill, 2010).  When compared to physically active men, MX athletes produce greater anaerobic power, aerobic peak power, and have greater muscular endurance (Bach, Kinsey, & Ormsebee, 2015).  Given that racers compete at near maximal heart rates (>90% HRmax) and high VO2, it is expected that MX athletes have significant cardiac adaptations.  Indeed, a study by Nagy, Vari, and Balogh (2015) found that A-level (semi-professional) Hungarian MX athletes had the same cardiac adaptations as professional or Olympic athletes.  Also, Anthropometric measures have indicated that MX athletes typically have less body fat than physically active men (Bach et al., 2015). 


There are two oft reported studies which have directly compared motocross riders to other athletes, one in 1979 by the National National Athletic Institute and another in 2002 by the University of Pittsburgh Medical Center's (UMPC) Sports Performance Complex.

Other studies:

"UPMC starts study of ways to cut down off-road motocross injuries", By Pohla Smith. Published Tuesday, July 23, 2002, Pittsburgh Post-Gazette,
"Are motocross riders athletes? Bikers and researchers say yes", Pocono Record, Aug 30, 2002.
"Motocrossers As Athletes", p106, Cycle World Magazine Jan-Feb 1981.
Transcript of interview of Brad Lackey by Bobby Myers about his participation in the 1979 NAHI study.
"The Exercise Intensity of MX and SX Racing", By Gay, D; Keen, J; Riel, R; Evans, M; Milek ,M; Furman, T; Casillas, E; Augustine, S (senior author) University of Florida HSC - Jacksonville and Jacksonville Orthopedic Institute. 
"Physiological characteristics of top level off-road motorcyclists". Gobbi AW, Francisco RA, Tuy B and Kvitne RS. BJSM. 2005; 39:927-931. - comparing off-road motocross, enduro, and desert rally motorcyclists. Motocross riders had more muscle mass, more strength, and greater aerobic power.
"Cardio-respiratory and neuromuscular responses to motocross race", Department of Biology of Physical Activity. University of Jyväskylä. by Tomi Konttinen. 2005.
"Cardiopulmonary loading in motocross riding Tomi Konttinen", Keijo Häkkinen, and Heikki Kyröläinen, Journal Of Sports Sciences Vol. 25 , Iss. 9,2007
Saltin, B. 1975. Motocross-ajajan maksimaalinen hapenottokyky ja syketaajuus ajosuorituksen aikana (Motocross rider's maximal oxygen uptake and heart rate during the riding performance). Teoksessa: Husqvarna 250-360 CR. Owner's manual. American edition. Värnamo. Sweden. 1976
"Anthropometric Characteristics and Performance Capabilities of Highly Trained Motocross Athletes Compared With Physically Active Men", Bach, Christopher W.; Brown, Ann F.; Kinsey, Amber W.; Ormsbee, Michael J. Journal of Strength and Conditioning Research December 2015 Vol. 29 - Issue 12: p 3392–3398. - results suggest highly trained MX athletes possess certain physiological adaptations that likely result from sport-specific demands compared with physically trained men.

Check out this article by Redbull on these athletes physical fitness and abilities.
https://www.redbull.com/gb-en/motocross-fitness