Every sport has its physical challenges, but 80 minutes of rugby, 48 of basketball, 10 seconds sprinting the 100 meters or two hours at the steering wheel of a Formula 1 car are all incomparable.
But what are the specific challenges involved in those two intense, energy-sapping hours driving an F1 beast and how do you prepare for them? Speed, G-forces to make your stomach churn, concentration ... It's all highly demanding, and will be even more so in 2017 with faster cars.
The drivers are going to have to be more physically fit than ever.
Carlos Sainz is heading into his third season in F1 with Toro Rosso, and it'll be a year that'll push him like never before.
"Our fitness levels of 2016 won't be any good for this year, so for that reason we need to step it up even more," explains Sainz, who's been locked into a new fitness regimen for weeks.
CrossFit sessions have been a staple.
"Instead of sessions of 50 minutes, which is normal, mine are between 1.5 and two hours — the length of a GP — and we're working at around 180-190 bpm heart rate. It also includes boxing and cardio work; it's relentless and we never stop working during the entire session. It's full-on physically."
Once the gym's done, 60-minute swimming sessions are next on the menu for Carlos's fitness feast.
A phrase that's often heard when referring to F1 and the subject of fitness in the sport is, "But if they're sitting down all the time, how can they get tired?"
Actually, the forces and resulting pressures the drivers' bodies are placed under require optimum levels of fitness, and it's for an extended period of time, too.
Legs, arms and the neck all have to be strong and able to handle some serious G-forces.
"We have two ways of training the neck. The first is with weights in the gym, which helps prepare for the G-forces we'll have to face in the car. The second is with a specific method when karting," Sainz explains.
Weights in the helmet when karting help drivers prepare for those G-forces in an F1 car.
"These weights make the helmet around three to four pounds heavier than normal, which corresponds to the kind of extra weight the G-forces will make me feel in F1. This, together with other specialized exercises, give the neck muscles a very good workout."
As if that wasn't enough, Carlos doesn't stop there. Between karting sessions, he uses a rubber band which loops around his helmet and is pulled by his trainer while he maintains form and position.
So there we have it. Even though an F1 driver sits in the same position for an entire race, the level of physical fitness and strength required cannot be underestimated.
Add to that the mental concentration that's necessary to race an entire GP, along with the pressures of performing, taking in radio communications, race strategy and more, and F1 drivers need to be in tip-top shape in every possible manner.