(CNN) -- You might not think to put a NASCAR driver in a marathon runner's shoes.But with the physical rigors that come with driving -- mostly unseen by spectators -- some industry insiders and drivers not only understand the similarity to long-distance running but also stress the importance of being physically fit for their careers.With 30 years of experience in motorports, Dr. Stephen Olvey, director of the neurosurgical care unit at Jackson Memorial Hospital in Miami, was determined to show that race car drivers measured up to traditional athletes.Olvey found that on an oval track like NASCAR's, drivers sustained heart rates 80 to 85 percent of their maximum, similar to the heart rate of a marathoner.Yet his findings were met with skepticism. Doctors and scientists attributed the spike to adrenaline and hormones; what an every day driver experiences in a "near miss."Olvey then joined forces with Dr. Patrick Jacobs, an exercise physiologist at Florida International University in Miami. The two set out to measure a driver's oxygen consumption. What they found was that drivers used the same amount of oxygen and energy as a long-distance swimmer or runner.Sports psychologist for Hendrick Motorsports Jack Stark stresses the non-stop nature of the sport."[In] football, you go hard for 15 seconds, rest 30-40. Basketball, you have time outs. You can't stop a race and get out of your car. You know, you're going hard for four hours."NASCAR driver Kyle Petty also likens what he does to participating in a marathon."You don't need to really peak at any given time and if you do peak, it needs to be at the end of your run when you can really kick," he says.Dr. Robert Cantu, a neurosurgeon at Emerson Hospital in Concord, Massachusetts, and an expert on motorsports, agrees that race car drivers are athletes, but says they don't need the speed or strength of other sports."They definitely need to have very keen eyesight. They need to be able to be focused, have very superior concentration, make split-second judgments, [and] have very, very good hand-eye coordination."The hot seatHeat is one factor present inside these cars which serves to break that vital concentration.During races, drivers are subjected to extreme temperatures -- over 100 degrees in the car and up to 170 degrees near the floorboards -- and despite the help of some air cooling systems, temperature is still a menace to the level of concentration drivers must maintain during a race. Olvey stresses the importance of being physically fit as a way to combat that threat, which can have serious consequences on the track."You'll see less fit drivers start to lose control and start to have accidents more often than they do early in the event or than the more fit drivers do," Olvey says.Further, Cantu offers this analogy: "You're essentially trying to function at a very high level of concentration in a sauna."While the heat is trying to break a driver's concentration, lateral G-forces are trying to throw them out of the car. For example, on turns drivers experience G-forces similar to those of a space shuttle on liftoff -- in their cars.Driving 'conditioning'Perhaps this is why some NASCAR drivers stress proper nutrition and workout routines, despite the busy schedule of a demanding season."I run 20-25 miles during the week ... but you really watch what you eat, I think that's the main thing," says Petty.Driver Jimmie Johnson is serious about staying in shape, too and equates good physical fitness to a better performance on the track."If you take a look at Mark Martin, he's been in the sport for a long time and at his age, the reason he's up front competing for wins and championships like he does is because he's in great shape," says Johnson.Now 46, Martin was one of the first drivers to begin seriously working out, in the late 80s. He's also written a book "NASCAR for Dummies" which highlights the importance of exercise.While driver Greg Biffle watches his diet, works out and stays active, he also sees racing alone as a form of exercise."We're in a race car three days a week which also keeps us in shape. You know, that's like working out... ," says Biffle.Racing a car is more than simply driving. With a race's intensity and length, NASCAR drivers may condition their bodies outside of work and on the job. Either way, they're making it possible to go the extra mile -- or last lap."You gotta have tremendous stamina and strength to be able to get in a car and go 200 miles an hour for four hours [in] very hot, difficult conditions where you're cramped in, and be able to move that car, and the G-force and upper body strength ... you gotta be a very good athlete," says Stark. "And you're reflexes have to be quick, you have to be able to see things, so it takes a tremendous amount of ability and skill, I think, to be a driver."