Le Mans Main Straight 2017

Imagine you’re a racing driver blasting along the Mulsanne Straight during the Le Mans 24 Hours, hitting speeds of 300kph as you overtake numerous cars in one go.

Now imagine it is 40°C in the cockpit, you are wearing three layers of overalls, a helmet and gloves, and you are tightly strapped-in to your seat. Sometimes racing is less enjoyable than it seems. It also requires high levels of fitness and preparation for all circumstances, particular sweltering temperatures in the cockpit.

During this year’s Le Mans, ambient temperature readings clocked above 30°C for the majority of the daylight driving hours, and were much higher than that inside the cockpit. “It is obvious that the drivers all suffer in these hot conditions,” says Dr Dominique Vivier, Chief Medical Officer at Le Mans.

“They are wearing fire-proof overalls, helmets and gloves, and they are driving within closed cockpits in which the temperature is high, even in normal conditions. Heatwave conditions are demanding – physiologically and psychologically – for the body, and drivers feel more tired as a result. This is why they must all be in excellent physical condition to race in endurance racing, and in the Le Mans 24 Hours in particular.”

The risk of driving in the heat is not merely one of increased tiredness, it can be truly dangerous in extreme cases.

“Effects related to high temperatures include fatigue, dehydration (which can lead to coma in certain cases), and body convulsions, which could pose risks by overtaking the body temperature regulation mechanisms,” says Vivier. “In medicine, malignant hyperthermia is characterised by body temperatures above 40°C and above. This situation can lead to hospitalisation in intensive care or resuscitation units.”


The human body is happiest at an optimal internal temperature of 37.5°C. The body is able to regulate its temperature in a number of ways – shivering when cold helps to raise the core temperature, and perspiring helps to send the temperature the other way, with the evaporating moisture cooling the body from the outside. But what if evaporation is hampered by numerous layers of clothing?

Professor Claude Meistelman, a lecturer at the University of Nancy, and expert in heat stress, says that developing a driver apparel solution that is both fireproof and sufficiently breathable is a fine balance.

“At a cockpit temperature of, say, 32°C, if the driver is wearing three layers of overalls with a lack of permeability, he will store heat very rapidly. More breathable overalls are more efficient in heat dissipation, and the rise in central core temperature is slower than with less well-vented overalls.”

One man who can attest to the sizzling weather in Le Mans this year is José María López, one of three drivers of the #9 Toyota LMP1 car.

“It was hot all weekend in Le Mans this year,” he said. “In the cockpit, it’s all closed. There’s no air coming in, so when you are in the car for two or three hours, it gets difficult”.

A full service stop in endurance racing takes roughly a minute and involves a change of all four tyres, as well as a brimmed fuel tank, and a swap of driver. Regular tyre/fuel stops take slightly less than this, but they are nonetheless one of the toughest parts of a race in hot climates.

“The worst time is when you stop, you don’t want to be in there a long time,” says Lopez. “There’s no air coming in, and all the heat is coming into the car because the engine is stopped and you’re not moving. The car is suffering, and you’re suffering too.”

Jose Maria Lopez le Mans 2017

López echoes Professor Meistelman’s point about heat storage and build-up being the key factors when it comes to driving in the heat.

“It gets uncomfortable in there,” he says. “When you first start, it’s okay, but the heat suddenly comes quite quickly. It’s most noticeable with the breathing, because you breathe hot air and you sometimes have this sensation kind of like you’re suffocating.

“That’s why racing drivers – especially endurance drivers – have to be fit, because we spend a lot of time in the car in conditions like this. We have to be used to the conditions, but there are races sometimes like at Le Mans and the Circuit of the Americas where it can be extremely hot in the car and difficult to manage.”

The Circuit of the Americas (COTA) – and more specifically the FIA World Endurance Championship (WEC) race there in 2016 – was one of the catalysts for a new heat-related rule in the championship which limits continuous driving time to 80 minutes if the ambient temperatures will reach 32°C. Race-winner Timo Bernhard described the conditions as “brutal”, with temperatures reaching 35°C during the race.

A heat stress study by Professor Meistelman documents that at the Acropolis Rally in Athens in 2001, the ambient temperature was 33°C, very similar to that seen in Le Mans this June. A by-product of this heat at the Greek rally was an internal cockpit temperature of 46.5°C in cars without air conditioning, and a core body temperature of 39.2°C for drivers of said cars, which can be a dangerous level at which to operate.

“Teams should understand that if the central core temperature of the driver is above 38°C, there is a risk that performance could be influenced” says the Professor. “I can’t say if this is equivalent to the driver losing a certain amount of time or driving a precise amount slower per lap, but he will be more prone to mistakes, such as going off, or spinning the car.”


Despite rigorous training regimes it is near impossible for drivers to truly acclimatise to hot conditions in a cockpit. “Some drivers expect an improvement in adapting to the conditions if they spend a few days in a hot environment before the race,” explains Professor Meistelman. “However, this is a hopeless endeavour, because adaptation to hot environments requires several weeks and is not guaranteed for anybody.”

Dr Vivier echoes this sentiment, saying it is “absolutely not possible” to acclimatise to driving in the heat. “One can’t train to overcome these high temperatures conditions. The human body is made to ensure an optimal, controlled temperature at 37.5°C.”

Since the body has no need to remain at a constantly high temperature, prolonged exposure to heat will do little for a racing driver other than to make them familiar with the sensation of warmth in the cockpit. “The body sweats to cool itself, and produces the sensation of thirst when it starts to dehydrate,” explains Dr Vivier. “However, the body temperature cannot significantly rise in normal conditions.”

Stuart Hall Aston Martin, CotA 2015

In a hot race, then, sweating really is a driver’s best friend. Air conditioning and other cooling techniques such as liquid-cooled underwear are ineffectual in the long run, making permeable overalls and sweating the first line of defence in body temperature regulation when driving in the heat. This, of course, means a lot of lost fluids.

“Hydration is important, but it’s not just a case of drinking a lot,” says López. “You need to be careful, because you might be told to drink three litres of water – but if it’s only water, you will wash all of the salts out of your body, and that will make things even worse.

“You need to take supplements, salts, and things that help you to retain the water in your body, which can be found in sports drinks. These will help you keep water in the body for a long time. If you only drink water, you will be going to the toilet every 10 minutes.”


Thankfully, the 2017 edition of the 24 Hours of Le Mans ran perfectly despite the extensive heat, according to Dr Vivier. This had much to do with preparation and messages of advice for teams, drivers, and spectators.

“Temperatures were at times above 35°C, and this was for several consecutive days with little to no cooling of the air overnight. I had fears in terms of the effects of these temperatures, not only for the competitors and their teams, but for staff around the circuit, and the general public who were present in large numbers.”

Close to 260,000 spectators were at the circuit over the week, more than doubling the town’s population of around 148,000. The volume of fans pouring into the venue means that there are two separate medical facilities; one for drivers, and one for the public. Packed grandstands all week coupled with the weather could have presented a higher amount of visits to the stands for medical staff, but Dr Vivier says it was business as usual.

“Heatwave weather conditions can cause difficulties for the Medical Centre, but activity was similar to previous years, both for the track Centre and the spectators Centre.”

There were 54 causes for medical extraction of spectators, and seven such cases for drivers on-track.

“Expertise and anticipation made the event run smoothly, and the public followed the prevention and awareness messages regarding the heat effects. In this situation, the right thing to do is to seek shade as much as possible and rehydrate steadily and significantly. When the sensation of thirst occurs, it means that the dehydration mechanism is already engaged, so it is important to have this rehydration reflex constantly.”

Auto Medical 11 Cover

This article has
been republished
with permission
from AUTO+ Medical,
the FIA’s Journal of
motor sport medicine