From the Tour de France: the art of hydration on the bike

Second and final installment dedicated to nutrition and hydration on the bike, as the Tour de France enters its decisive phase. In the first episode we talked about food and carbohydrates; today we focus on fluids — with the practical advice of Laura Martinelli, Lead Performance Nutritionist for the WorldTour Team Jayco Alula and Liv AlUla Jayco, who has worked in professional cycling since 2013 and also supports the number one in French tennis, Arthur Fils.

If there is one topic on which even the most attentive amateur tends to improvise, it is hydration. And yet, as Laura Martinelli explained to us, this is precisely where a few simple actions make an enormous difference — not only for performance, but also for safety on the bike.

Let’s see how professionals approach the subject and what we can borrow for our own rides.

The good news is that only a few daily habits are needed to obtain a reliable picture. “The scale is the fundamental tool,” Martinelli says.

The first action is weighing yourself on an empty stomach every morning, after going to the bathroom: if body weight remains stable, with the physiological fluctuation of half a kilo, it is a good sign. It should be read together with the color and frequency of urine, which should be abundant and clear, with an indicative reference of six to eight urinations per day.

The most revealing action, however, is weighing yourself naked before and after training — naked, because sweat‑soaked clothes would distort the measurement.

From that double weighing comes a valuable practical rule: “For every kilo lost, I know I need to drink a liter and a half before going to sleep.” A liter and a half, not one, because the body remains overheated and continues to consume water even after the effort. And there is an alarm threshold: losing more than 2–2.5% of body weight during the ride means drinking too little, and that next time, under the same conditions, it is wise to anticipate.

To give an idea of how extreme certain situations can be, just look at the Pyrenean stages of the Tour: “Sweat rate can reach up to two and a half liters per hour,” the nutritionist says. “In extreme conditions, you can exceed eight to ten liters of sweat in a five‑hour stage.” Numbers for professionals, of course, but ones that clearly explain why hydration should never be improvised.

Here, too, however, there is a caveat Martinelli always makes: these are male figures. In women’s cycling, sweat volume is generally about half — roughly between 0.5 and 1.2 liters per hour — both due to body size and power output, and because races are shorter. The numbers change, not the method: the scale and the double weighing remain the right tools to understand how much one truly sweats, whatever the starting point.

Drinking a huge amount the day before the ride, convinced you’re stocking up? It works less than one might think. “The kidneys adjust excretion within a few hours,” Martinelli explains: if on Saturday I drink five liters ahead of Sunday’s long ride, the body simply eliminates the excess.

The smart strategy is another: “The key window is between the end of breakfast and the start of training. If in that window you drink more and take in a bit more sodium, the kidneys don’t have time to adjust excretion.” The result? “You end up with your tanks full without having lost sodium.” It is, indeed, the camel technique done at the right moment, with the only caution of not weighing yourself down if the ride starts immediately uphill.

Here nutrition becomes very concrete. The team works with four types of bottles: plain water, one with electrolytes only — the “salt bottle” — and two with different carbohydrate concentrations, 40 and 80 grams. “I strongly believe in keeping electrolytes and carbohydrates separate: it’s my personal approach,” Martinelli notes.

The logic of 40 versus 80 is a balance to manage. “The more carbohydrates I have in the bottle, the greater the energizing power, but I lose hydrating power,” she explains. “When it’s hotter, I use the 40‑gram bottle; when it’s colder, the 80‑gram one.” Translated: in the heat, the priority is hydration, so the concentration is lowered; in the cold, energy intake can be increased. A principle anyone can adopt by alternating their bottles according to the day, the temperature, and the duration of the ride.

And during the ride, how is everything distributed? “In the end, it’s a bit of math,” the nutritionist smiles. The rule she gives riders is simple: the carbohydrate bottle acts as the liquid base, to be sipped continuously, while bars and gels — typically 30 to 45 grams of carbohydrates each — are taken at regular intervals, depending on the stage profile. Liquid and solid alternate, with the liquid providing the constant foundation.

If there is one element that should never be underestimated, it is sodium. “It is the electrolyte most lost through sweating and is also involved in carbohydrate absorption at the intestinal level: for me, it is the prince of hydration,” Martinelli states without hesitation.

She sums up the reason why she cares so much in a sentence that applies to any amateur as well: “I’m not only interested in hydrating; I’m also interested in retaining the water I drink.” And that is exactly what sodium allows you to do. Without an adequate intake, even the best carbohydrate strategy is less effective.

We tend to think of dehydration as a problem linked to high‑level performance. In reality, it happens more often than one might think: it’s enough to forget the bottle in the freezer before a lunchtime ride, lose it on a pothole during a descent, or fail to find a fountain at the right moment.

And the impact is immediate and subtle. “The first thing to be affected is the perception of effort, the ability to make decisions, the ability to stay focused,” Martinelli explains. Only afterwards does the actual physical decline arrive. The point is that, on the bike, the loss of clarity carries a different weight: “When I work with a cyclist, compared to a tennis player, I have an additional risk factor: on the bike we are on the road,” not in a protected environment like an indoor court. Less focus means a higher risk of getting hurt.

On the physical side, the consequences arise because “all metabolic reactions occur in a water‑rich environment”: when hydration is lacking, muscle contraction can be compromised — hence cramping, even if the correlation is not always linear — and even blood pressure, due to changes in plasma volume.

The most insidious risk, however, is the vicious cycle: if you tackle intense effort already dehydrated and less lucid, you further increase the load. “Sometimes it’s simply a matter of stopping or slowing down when needed,” the nutritionist reminds us. A piece of advice as banal as it is valuable.

When asked for three rules to “borrow” from professional protocols and bring home, Laura Martinelli replies with three simple pillars to remember.

1. Never start in deficit. “It’s much easier to eat and drink off the bike,” she explains: the riding position does not facilitate digestion, and any fuel taken too late becomes passive weight. Better to use the time before the ride to start with full glycogen and fluid reserves.
2. Eat and drink before you need to. “When you feel hungry or thirsty, you’re often already late.” The key word is planning: “Don’t drink later if you can drink now, don’t take the gel later if you can take it now.” Many factors on the bike cannot be controlled; nutrition and hydration, fortunately, can. “We control what we can control.
3. Personalize. “The strategy of my riding partner may work for him, not for me.” In a world full of social media and “super‑experts” in nutrition, word of mouth can offer ideas, but should not be followed blindly: that gel or supplement that works for someone else may not work for you.

The most important message, at the end of these two installments, is also the least eye‑catching.

“There is no supplement that saves performance, or at least, if it exists, it isn’t legal,” Martinelli says bluntly. And she adds the sentence that sums up the entire philosophy: “We are the habits of the last two, three, four years.”

Even the most cited aids must be put into the right perspective. Bicarbonate and other tricks, she says, “should be understood as the cherry on the cake: but I need the cake first.” Translated: no product works miracles on a foundation that doesn’t exist. “There is no secret of the professionals, there are no magic products, otherwise I’d probably be doing another job.”

It is an invitation to be wary of shortcuts. Marketing gladly sells the magic potion, because it’s easier than saying “take two years to build healthy habits.” But the truth, repeated by anyone who has competed at a high level, is that performance is the sum of many ordinary things done consistently: sleep, nutrition, training, recovery.

For amateurs, this also means knowing how to give up: stopping when tired, skipping a long workout after two bad nights. “Knowing how to listen to yourself and maintain good practices is the first way to stay healthy,” even before being performant.

Then, on top of a solid foundation, the details — the right bottle, the right grams, the sodium at the right moment — truly make the difference. Never the other way around.

The information contained in this article is intended for educational purposes and does not replace personalized nutritional advice. To set up a tailored strategy, it is always advisable to consult a professional.