SINGAPORE -- For Formula One drivers, the Singapore Grand Prix represents the toughest physical challenge of the year. A combination of heat, humidity and a race that regularly runs to its two-hour time limit, makes for a serious workout for the body. Add into the mix the mental challenge of threading a car between concrete barriers at speeds of over 180 mph, and the race in Singapore is truly a challenge unlike any other in the world of sport.
Over the course of Sunday's race, each driver's body will be fighting a losing battle against dehydration and heat stress. Aside from the obvious physical discomfort they cause, the other concern is the impact they have on mental performance and concentration levels. Much like an F1 car, the body needs specific preparation to operate as close as possible to its peak during the Singapore Grand Prix, and drivers and their trainers go to great lengths to maximise performance. But even the fittest drivers are close to their limit, and if things go wrong, the cockpit of an F1 car at Singapore can quickly become an intolerable environment.
In 2014, Danish driver Kevin Magnussen -- then racing for McLaren -- suffered minor burns from his seat when hot air leaked from the radiator into the cockpit. Already dealing with ambient temperatures of 30C and humidity at 80%, the added heat from the leaking radiator pushed conditions in the cockpit to a potentially dangerous level.
"It was completely terrible," Magnussen recalls. "I can't remember the last half of the race -- I was just waiting to blackout. I was so hot and I was overheating, sweating and dehydrated. It was like racing in a very hot sauna."
Magnussen's reward after two hours of racing was a 10th-place finish, and with it, only one championship point. So was it worth it?
"I just accepted that I might blackout at some point," he added. "You just try your best. You don't know if you are going to blackout, so there is no point giving up."
Magnussen's 2014 race is an extreme example. For the most part, drivers are able to deal with the heat and use techniques that have been expertly honed over 12 years of racing in Singapore. Dr. Luke Bennett, medical and sports performance director for F1-health specialists Hintsa Performance, works with more than half of the drivers in Formula One, including reigning champion Lewis Hamilton. Now that the Malaysian Grand Prix -- which also took place in an equatorial climate, but during the day -- has dropped off the calendar, Bennett says there is a "pretty strong case" that Singapore is the hardest race of the year both physiologically and physically.
"I haven't seen evidence of physiological danger at this race, but I think it's fair to say that if you go into the FIA's driver area at the end of this race it looks like an absolute war zone in there," he told ESPN ahead of the 2019 race. "The colour in the drivers' faces -- they are red, they are panting, they are soaked in sweat, they've got this far-away look in their eyes. It's definitely different to other races."
The heat and humidity present two main challenges for the body and they emerge in two distinct forms.
"One is dehydration -- so the level of fluid volume that you have in your body -- and the other is heat stress," Bennett says. "They can be related and can coexist, but are actually distinct entities.
"The science would say that to maintain good cognitive function at a level of a fighter pilot or Formula One racer, you shouldn't drop below 1.5 to 2 percent dehydration or body-weight loss.
"Interestingly, you can go much higher than that for a marathon or ultra-distance triathlon when perhaps 3 or 4 percent is even optimal. But when you are trying to maintain cognitive faculties like a Formula One driver, about one-and-a-half to 2 percent is the ideal limit."
Typically, a driver will lose as much as three kilos of body weight through sweat during the two-hour race in Singapore, which is the equivalent of three litres of fluid. Depending on the driver's starting weight, which can be anywhere between low-60 kilos for shorter drivers and as much as 75 kilos for taller drivers, they are experiencing somewhere in the region of 4% to 5% body-weight loss by the end of the race.
Each car is fitted with a drink bottle to replenish those lost fluids, but the size is often determined by car design -- and in Formula One performance always takes precedence over driver comfort. Regulations allow the bottle to be up to 1.5 litres in size, but it's often just 500ml or a litre to save weight. What's more, the temperature of the drink is not immune to the conditions in Singapore and is often likened to "drinking tea" during the race.
Heat stress is different to dehydration and relates to how efficiently the body dissipates heat. At the extreme end of the "heat illness" spectrum is heatstroke, which is when body temperature exceeds 40C -- often resulting in symptoms such as a throbbing headache or nausea and vomiting.
"Every person and individual has a different capacity to dissipate heat and there are different ways that we can dissipate our body heat, and some people are better at it than others," Bennett explains. "You might be better at sweating, you might have less body fat that allows heat to radiate, you might just run a lower metabolic rate, which means you just run cooler.
"Every individual is different and some people seem genetically predisposed to these heatstroke illnesses. It may be that there is actually not much preparation you can do for people like that, where it is just something about their make-up."
As a bunch of fit athletes in their 20s and 30s, F1 drivers are already well equipped to deal with heat. But even so, preparations for the challenge of the Singapore Grand Prix usually start long before a driver has even checked in for their flight.
Research has shown that exposure to higher temperatures several weeks in advance of the race weekend helps the body perform when it matters. It's also why the French Grand Prix, which is usually the first hot race of the European season, presents a surprisingly physical challenge as it comes after cooler races in Monaco and Canada. Different drivers go to different lengths to prepare for hot races, but the chances are all trainers will tweak their driver's regime in the weeks leading up to the Singapore Grand Prix.
"Our coaches and drivers are thinking about these hot races well ahead of time," Bennett says. "It's surprising how short a period of time you can gain useful heat adaptation -- so even a week, but typically two or three weeks, can make a big impact on how your body will handle this particular event.
"It might be coming out to Asia and training in an equatorial area in these conditions; it might be using a formal heat chamber at one of the universities in London that we are associated with; or it might be something as simple as dragging an exercise bike into a sauna to do some training sessions. Training with lots of excess clothing and training in a driving suit -- they are actually relatively simple remedies, but they can have a really big impact in a pretty short period of time."
Williams driver George Russell is competing in his first Singapore Grand Prix this weekend and is among the drivers who have been layering up in the gym in recent weeks.
"I haven't cycled in saunas, but for the last 10 days, every gym session I've done I've been wearing tights, long socks, tracksuit bottoms, long-sleeve T-shirts, a jumper and a rain jacket with the hood up," he said on Thursday. "Last time I was at Williams' factory, we were at the gym and my trainer turned the heating up to 28C and I had all of these clothes on as well.
"I finished at lunch time and all of these staff members came into the gym for their training session, for which the temperature is usually set at 19C, and they were like, 'What the hell have we walked into?' So they weren't too pleased about that."
Preparations continue right up until the start of the race, with drivers wearing specially-designed cooling vests and ice towels around their neck to keep core body temperatures in check. Known as pre-cooling, it can help prevent the onset of heat stress for the first hour or so of the race. "Typically, you'll see the drivers with various commercially-available cooling vests," Dr Bennet says. "We also use fans, ice-packs on large blood-vessel beds around the neck, dry-ice around the car -- although you have to be careful not to have too much ambient carbon dioxide in that circumstance.
"Also simple things, like getting into the car as late as possible and cool drinks. The cockpit environment is very tight and there is very little airflow at 200-300 km/h, so if you can drop your body temperature leading up to a race, you do buy yourself some time before that stress impacts in the second half of the event."
But the heat is not the only challenge in Singapore. As F1's only true night race -- both Bahrain and Abu Dhabi finish in the dark, but start under a setting sun -- the Singapore Grand Prix schedule is also unique. Rather than adapt to Singapore time, the teams typically keep their body clocks ticking on the time back home, with Sunday's race starting at the equivalent of 2:10pm Central European Time. The result is dinner times around 3am and alarm clocks set for the early afternoon before the paddock starts to fill up around 2pm and the working "day" gets underway.
"I think it's fair to say, honestly, that our approach to this race is still evolving," Bennett says. "There is an approach that keeps people on European time and, in theory, has a pretty limited circadian impact, but there is something different about this race and it's probably the brightness of the ambient lights at night, which means it's just not that simple.
"Even the best prepared driver, engineer or team member will get to a pretty big circadian displacement travelling to this event. It depends a little bit on what events we have before and after -- we used to do Singapore back-to-back with the Japanese Grand Prix, which was brutally difficult switching from Sunday to Monday with a new timezone and heading an hour further east. Singapore as a standalone race is not too bad and with Russia next week it is not too bad either.
"We use all of our usual techniques, so trying to adapt to the new timezone a couple of days before departure, using exposure to light and darkness at the correct times -- or as far as you can control that once we are here in Singapore.
"Exercising and eating at the right times, maybe using a supplement like melatonin. Those techniques are itinerary dependent and we are lucky enough to work with Professor Steven Lockley at Harvard University, who will prepare hour-by-hour, bespoke, hand-prepared plans for each driver depending on their precise flights and schedule."
All of the above make the Singapore Grand Prix unlike any other race on the F1 calendar. Much like the skinny rear wings at Monza or close barriers of Monaco, the Marina Bay circuit has its own unique challenge, and for that very reason it is both loved and loathed in equal measure by drivers, including four-time Singapore race winner Sebastian Vettel.
"I think it's a kind of love-hate relationship because it's the toughest race of the season, it's the longest race that we have and physically one of the most challenging," the Ferrari driver said on Thursday. Obviously there are no high-speed corners, but it is hot in the car and very humid and you need an incredible level of focus driving here.
"You want to prepare as best as you can, but ultimately you want to get going once you get here, hence the love-hate relationship."