Formula One is a physically grueling and mentally taxing sport, even for the experienced. Drivers must withstand up to 3.5 g's of cornering force, turn after turn, for races that cover nearly 200 miles and last up to two hours.

They wear fireproof suits and are crammed into cockpits that get so hot, they can drop 6.5 pounds in body weight between flags. They're driving north of 200 mph—about 300 feet per second—sometimes just inches apart from one another, with visibility not unlike poking your head out of a well. And if their energy or concentration lapses for even a moment, it can cost them time, a dropped position, or even a crash.

They run 20 races in 20 countries, in eight months. They race in extreme humidity, heat, or rain, sometimes just days after your last race. They must have each track perfectly memorized, and then be able to adjust on the fly to account for changing conditions. Only then can whatever talent they have as a driver make a difference.

For rookies, it's even tougher.

Max Verstappen and Carlos Sainz, Jr. have shown plenty of that talent this season. At the start of the 2015 season, Sainz was 20, Verstappen just 17 (both had birthdays in September). That makes Verstappen the youngest F1 driver ever—and since the rules now bar anyone under 18 from competing, he'll hold the record indefinitely. Both rookies drive for Scuderia Toro Rosso, a mid-field team created in 2006. With two races left in this 2015 season, they've earned their place on the starting grid. Sainz has seven top ten finishes in 17 races. Verstappen has nine, plus a pair of fourth place finishes. They're ranked 15th and 10th out of 20, respectively.

Despite their youth, it's no surprise the two rookies ended up in Formula One. Sainz's father, Carlos Sainz, Sr., was an all-time great rally driver. Verstappen's father Jos was a successful F1 driver. His mother, Sophie Kumpen, was a professional kart racer. The Toro Rosso drivers followed the same career trajectory, starting off racing karts as children in Europe, then moving into lesser Formula series (think minor leagues) before being called up to the pinnacle of motorsports this year. They came in knowing how to handle four wheels and an engine, how to do starts, how to overtake. With just two races left in their debut season—the Brazilian GP today, and the Abu Dhabi GP November 29—they've learned far more.

The key difference in F1, Verstappen says, is "You have to be much more professional." Mostly, that means spending your time training. That happens in three distinct places: at the gym, in the simulator, and on the track.

In the Gym

Time in the gym isn't about getting ripped, it's about crafting your body so it's capable of standing up the brutal conditions of an F1 race. That means lots of time swimming, cycling, and running to stay fit, up to four hours a day during the three-month preseason. The drivers work with weights for their arms and legs, but not too much.

Muscle is only necessary to a point. The combined weight of the car and driver must be at least 1,523 pounds. Every pound of that you can take off the driver, you can replace with ballast, and strategically locate it to your advantage. Coming into this year, Sainz had never followed a diet before. Verstappen was used to going to McDonald's once or twice a week while racing in Formula 3. Now they obey their nutritionist, eating five to six small meals a day. Lots of greens and protein, minimal carbs.

Both of us showed already the whole season, we were very competitive. Max Verstappen

The muscle that gets the most work in the weight room is the neck, which has to keep the head and helmet upright through all those turns. Verstappen and Sainz spend time lying horizontally, with weights strapped to their head, working to match McLaren driver Fernando Alonso, who once used his neck to crack a walnut. Each seems to have borrowed his neck from a rhinoceros.

The Simulator

Fitness is key, but it's no good without knowing the quickest way around a track. Drivers memorize each circuit, and it's more than remembering "left, left, right," and so on. They know exactly what gear they should be in at any given point, where to brake, where to slam the accelerator. That process starts with your basic kind of homework: Studying data from previous years, watching onboard video feeds from past drivers, with a focus on those who are especially quick on given tracks or corners, and talking to team managers.

Then it's into the simulator. Sainz and Verstappen spend up to two days a week virtually racing circuits around the world, while actually sitting in Milton Keynes, England. The graphics aren't mind-blowing, but the tracks are faithfully recreated, which is what drivers, especially rookies, need to get familiar. The drivers sit in a mock cockpit, helmet and gloves on, with a fully realistic wheel in their hands and the real nose of the car between them and wraparound screens displaying their "surroundings." The half-car sits on a flat platform that moves side to side to simulate motion, but can't create realistic g forces.

Both rookies have raced some of the European circuits on the F1 calendar in other series, but places like Bahrain, Singapore, Brazil, and Austin are totally new. This is where they start to figure out where they'll shift gears, which turns they'll take early, where they'll hold off as long as possible before hitting the brake pedal. "It gives you a great hand," Sainz says.

Track Time

The simulator's key, because thanks to rules restricting how much time teams can spend running their engines during a season, drivers aren't allowed onto their test tracks whenever they want. The computer is maybe 95 percent accurate, Verstappen says, but it misses key elements of an F1 race.

You don't get the g-forces or the heat of a real cockpit. You don't feel how the balance of the car shifts as you burn through fuel reserves. You don't see how the grip of the track changes based on the day's conditions, how that evolves as the cars lay down rubber and your tires degrade. "All those things, you need to learn," Verstappen says. That's where the three practice sessions held on Friday and Saturday of each race weekend come in handy.

And yet, talent still matters. At the US Grand Prix in Austin last month, despite losing most the scheduled practice time to heavy rain, Sainz finished in seventh place, Verstappen in fourth. At the most recent race in Mexico, Sainz took 13th place, Verstappen ninth. Toro Rosso has been surprisingly competitive for a team with only rookie drivers on the track. "Both of us showed already the whole season, we were very competitive," Verstappen says. "So maybe we didn't even need a veteran next to us."