Sun, sweat, and sodium: How the pros manage hydration

Some of this summer's racing, including at the Giro d'Italia Donne and the Tour de France have been stiflingly hot. Some days at the Tour the riders saw temperatures of 35 degrees Celsius, and more. So as the scorching July sun bore down relentlessly on the peloton, riders were forced to summon every ounce of strength, endurance and mental fortitude to conquer not only their rivals, but also the challenges of racing in extreme heat. 

Hydration is the cornerstone of performance in any athletic endeavour, and professional cyclists are certainly no exception. As they face intense exertion in the heat, the body sweats profusely to cool down, leading to a significant loss of fluids. And riders do not want to experience dehydration as it can pose a severe threat on their performance and wellbeing. But it is not only water that is required to stay hydrated. 

“Drinking too much water can actually cause you to over-hydrate,” Chris Harris sports scientist at Precision Fuel & Hydration said. “This can lead to electrolyte imbalances and even a condition called hyponatremia, low blood sodium levels.” 

So finding the right balance is important, especially for high-performing athletes who need to perform at their very best. Many teams work with hydration experts like Precision Fuel & Hydration to nail their hydration strategy in big races like the Tour de France. But how do they find out how much riders sweat and how to replace what they've lost?

Sweaty-mess, or cool, calm and collected? 

Everyone is different and that also comes down to how much an individual sweats and how much salt (or sodium) they lose during exercise. “With our testing, we’ve found that athletes can lose as little as 200mg of sodium per litre of sweat, all the way up to 2,000mg/l,” said Harris. 

Sometimes riders can be seen with a kit covered in salt after a hot stage where they’ve sweated a lot and this can demonstrate that they are on the higher salt levels, whereas other riders' kits may just look wet. The amount of sweat and sodium someone loses is mainly determined by genetics and is relatively stable after infancy, so it’s not a changeable factor. But this works in an athlete's favour, as once they know their levels, they’ll then be able to hydrate optimally for the foreseeable future. 

Riders who work with Precision Fuel & Hydration from teams such as Lotto Dstny will undergo a sweat test so experts can personalise a hydration plan for those heading to race a Grand Tour. But the test does not involve running on a treadmill or subjecting the riders to a gruelling test, rather a small patch is placed on their arm that allows experts to take a small sample of sweat to test the levels of sodium. 

“Every team has salty sweaters who need to be more proactive with fluid and electrolyte replacement. From the thousands of sweat tests we've done over the years, the average loss in the peloton will be around 950mg of sodium per litre of sweat. The wide variance either side of this average is why a one-size-fits-all approach to hydration just doesn't cut it," Harris said. 

Victor Campenaerts had his sweat tested to help him dial in his hydration strategy for his summer races (By Tim de Waele/Getty Images)

Replenishing the sodium stores

“Your body can’t produce or store salt beyond a certain point, so you need to consume sodium to keep your levels topped up,” Harris said. This is particularly important when riding in the sweltering heat. 

Some riders have stickers on the top tube of their bikes, which serve as visual reminders of the stage profiles or their personalised fuelling plans. These stickers are valuable tools that indicate when and how much water to drink or when to take gels or electrolyte supplements. For example, a sticker might remind a rider to consume a gel or a specific amount of water at the 50-kilometre mark to ensure proper fuelling throughout the stage and avoid the dreaded bonk.

Individual riders have different characteristics and needs, and some athletes are considered salty sweaters, so therefore lose more sodium through sweat than others, making it vital for them to consume more electrolytes during a race to maintain optimal performance and prevent potential issues like muscle cramps or dehydration.

However, hydration and sodium intake are not only critical during the race itself; they also play a crucial role before and after. Pre-race hydration is essential to prepare the body for the forthcoming fluid and sodium loss during the race. Starting the race with proper sodium levels helps mitigate the impact of subsequent sweating and fluid loss, giving the rider a better chance to maintain their performance levels during the stage.

This year's Tour de France has been extremely hot (Marco Bertorello/AFP via Getty Images)

Similarly, post-race recovery is crucial for riders participating in multi-stage races where they face consecutive days of intense racing. After completing a stage, replenishing lost sodium and fluids is essential to recover from dehydration and fatigue, helping the rider to prepare for the challenges of the following day. 

Managing hydration and sodium levels is therefore a crucial aspect of a cyclist's performance. The careful balance of electrolyte intake, especially for "salty sweaters" can significantly impact their ability to perform at their best and maintain their strength and endurance throughout the demanding stages. By putting in place effective fuelling strategies and paying close attention to their hydration needs, riders can optimise their performance and increase their chances of success in races like the Tour de France.

To learn more about Precision Fuel & Hydration or to learn your sweat score, visit: https://www.precisionhydration.com 

*Cover image by David Ramos/Getty Images