Beat the heat – how pro riders hydrate and acclimatise during the Tour de France

Nineteen years have passed since the defining image of the 2003 Tour de France. Joseba Beloki, descending the Cote de la Rochette like his contract depended on it, crashed in the final kilometres of stage nine into Gap. Lance Armstrong, close enough to enjoy a Beloki draft, miraculously avoided the Spaniard, remained upright over a parched field, dismounted, leapt over a drain and remounted the other side.

The Texan would win the fifth of his seven titles, which were later stripped after confessing all to Saintly Oprah. As for Beloki, he broke his elbow, femur and wrist, and would never again race to the same level, all because of a sticky strip of Hautes-Alpes tarmac that’d begun to melt in the heat that reportedly hit over 40°C at roadside. It prompted ASO to deploy water tankers ahead of the peloton in such brutal conditions. 

Beloki’s misfortune was an anomaly but does highlight, albeit with a hyperbolic edge, that heat is one of the greatest obstacles for riders to overcome at the Tour de France, especially as the race weaves its way south, this year firstly navigating the Alps and then heading further south-west to the Pyrenees. It’s why teams pay so much attention to adapting and hydrating their riders – as you’ll soon discover…

Related: Three nutrition mistakes and how to avoid them

ACCLIMATISING IS KEY

‘There are a number of physiological and biochemical as well as perceptual markers of heat acclimatisation,’ explains Mike Tipton, professor of human and applied physiology at the University of Portsmouth. Tipton’s area of expertise is preparing humans for extreme environments, and he’s worked for a number of sporting teams and federations including the England football team and Royal Yachting. ‘Over the course of around 10 days of heat exposure, you’ll find sweating increases, salt content in sweat decreases and heart rate decreases for a set workload. In short, an athlete feels better and is similar to how we might feel at the end of a two-week holiday in the sun. Seen through an elite-cycling lens, these changes are performance related. You can perform at a higher level because you can offload heat and maintain power output.’

Much of these heat-friendly physiological adaptations are down to the plasma volume of the blood. This constitutes around 55% of total blood volume, and is composed of salts, lipids and, importantly, 90% water. When you’re dehydrated – accelerated in the heat – water’s drawn from the blood plasma to the skin for cooling purposes. This reduces plasma volume, meaning less blood is pumped around the body with every beat. In an effort to maintain power output, the heart beats faster to deliver oxygen to working muscles, cranking up cardiovascular strain. The rider fatigues, power drops and its goodbye maillot jaune. Or it would be but the body cleverly expands blood plasma volume through heat exposure, leading to those heat-friendly adaptations.

These changes can either take place in a hot environment or in an artificial heat chamber. The latter can be found in advanced training tents like that used by Ineos Grenadiers’ Tom Pidcock in the build-up to his victorious mountain-bike outing at the 2020 Tokyo Olympics. Tipton’s academic institute at Portsmouth has a chamber, too, as do the likes of Loughborough and Bath universities. Or riders can go old school like Chris Boardman, who would often turbo train in his Wirral abode with the heating on and windowsills taped up to avoid cooling drafts.

Heat acclimation matters. As does a rider’s fitness. You see, the likes of Pidcock and his WorldTour contemporaries unknowingly become acclimated simply by racking up the miles. ‘There are a host of factors that identify people who are more susceptible to heat illness and one of them is low aerobic fitness,’ says Tipton. ‘That’s because there’s a strong correlation between an individual’s aerobic capacity and their ability to offload heat. The fitter you are, the more able you are to maintain a stable, deep-body temperature. 

‘From research, we know that if someone’s working at half their aerobic capacity, their core temperature reaches around 38°C [around 36.5°C is the norm at rest; shoot up to 39.5°C and warning signals could sound]. This is important because if you and I do the same amount of work and you’re twice as fit as me, your core temperature will be less. Managing heat and growing fitter have many physiological crossovers like sweating more and better peripheral bloodflow, which is essentially a coolant in this situation.’

21ST-CENTURY SOLUTION?

The importance of core body temperature on performance was noted by a Zurich-based technology business, who created the Core sensor. This is the first wearable that purports to measure your bodily temperature in non-invasive fashion. You don’t need to swallow an e-pill and there’s no rectal invasion. Instead, the sensor either sticks to your chest or is clipped into a chest strap. In both cases, it records the thermal energy transfer. As heat passes from the chest through the sensor, it generates a voltage signal proportional to the energy passing through, which ultimately gives a core reading. 

Core has validated the results, though a study out of the Swedish Sports Centre concluded that the sensor underestimated readings, which isn’t ideal when such a narrow core bandwidth is the difference between optimum power and heat stroke. Still, that hasn’t stopped seven Tour teams from using the product: Bora-Hansgrohe, Ineos Grenadiers, Quick-Step Alpha Vinyl, Trek-Segafredo, Movistar, Astana Qazaqstan and Lotto Soudal. In women’s cycling, Core’s publicly used by Canyon-Sram, Ceratizit WNT, Trek-Segafredo and Edelweiss Squad.

Why is down to its potential ability to help with pacing strategies, judge how acclimated a rider is and understand the general health of a rider, which is especially important over a three-week Grand Tour. As with TrainingPeaks and heart-rate variability data, the more a rider uses the tool, the more useful the sensor becomes, especially as how a rider responds to rising core body temperature is highly individual. This from Christopher Jones of Core, who reflects on last year’s Tour.

Related: How to train in heat

‘For stage 14 of the 2021 Tour de France, we focused on Simon Clarke of Team Qhubeka NextHash for a 100km segment, specifically the ascent of the Col de Montségur at 1,059m with 4.2km at an average gradient of 8.7%.

‘This section and the following ascent up the Col de la Croix de Morts saw the fastest increases in Clarke’s core body temperature reaching, 39.2°C. The gradient of the climb correlates to the increase in temperature. The steeper the ascent, the faster the increase in core body temperature. This is because of the increased physical intensity and also because there is less cooling from the wind at slower speeds.

‘During descents, the fast wind speeds rapidly accelerate the cooling of sweat through evaporation and Clarke’s fast descent from the Col de Montségur allowed him to lower his temperature to 38.1°C, which is below his starting temperature before the climb.’

Okay, there’s a sense of logic about this, but you can start to see how performance teams can unpick the data and assess pacing strategies and race tactics for the next stage based on the previous day’s intensity and core temperature readings.  

DEHYDRATION IS THE ENEMY

It’s early days and arguably unproven – unlike a team’s hydration strategy. Over to Robin Scheijen, nutritionist at Team DSM, to tell us more. ‘On a really hot long day, we’re looking at around 10 to 12 bottles per rider. Logistically, that’s clearly a lot for the soigneurs to manage and is over 2,000 bottles during the Tour.

‘We ensure they’re hydrated from the moment they arrive at breakfast and, beyond the fluid aspect, sodium and electrolytes are key for fluid balance but you also lose both through sweating. For a couple of years now, we’ve worked with a UK company called Precision Fuel & Hydration who’ll sweat test our riders at training camps. We can find out via a small machine the exact sodium composition of the sweat from each rider who are then classified into green (low), orange (medium) or red (high) groups. We then choose a suitable sodium-containing tablet from the range, which come in at 500mg, 1,000mg or 1,500mg sodium.’

Riders can be sweating out over 1.5 litres on a sweltering Alpine stage. Covering those losses is difficult on two fronts: the practical side of slurping from a water bottle so often, especially on an ascent; and the physical side of absorbing so much fluid. It might be manageable for an hour but the deeper a rider digs into a stage, the more uncomfortable the gut becomes. But if a rider can drink 750ml to a litre an hour, the team are generally happy and the rider shouldn’t be too dehydrated come the finish.

‘If they are, the team will know from their post-stage weigh-in,’ says Tipton. ‘Like many sports, especially in the heat, the team will have riders on the scales before and after. The best teams we’ve worked with do all that plus they do it for the support teams as well, the rationale being that if the support team aren’t performing at 100%, they can’t fully support the riders.’

The riders also use a urine chart to check pee colour. The lighter the better with dark brown screaming dehydration. ‘I know some teams might also use the specific gravity test, which is essentially a dipstick that tells you the concentration of urine. Again, it’s about finding out hydration status,’ adds Tipton. ‘It’s also worth noting that it’s better to sip than great volume in one go as it’s better absorbed. And preferable flavoured and chilled.’

That chilled aspect brings us back to Team DSM and their cooling confectionary of the past few seasons. ‘Our riders will drink slushies in the heat, especially before a time-trial,’ says Scheijen. ‘We have our own Slush Puppy machine and it helps to lower core body temperature. We also use ice vests before a hot time-trial and socks filled with ice.’ These socks or tights are filled with ice. The rider then places it on the nape of their neck to deliver a cooling effect close to the brain.

As temperatures increase in the Tour de France 2022 as the race rolls south, whoever can keep their cool when the mercury rises will be the one who’ll mount the Parisian podium. Weeks of sodium, sweating and suffering awaits…

Cover image: Pauline Ballet/ASO