Hydration advice is confusing. At one time athletes were told to drink as much as possible during exercise. Later, advice shifted to only drinking when thirsty.
More recently, research has suggested “prescribed drinking” may offer an advantage when dialing in a hydration strategy. If you thought hydration couldn’t get more complicated; enter drink mixes, electrolytes, and salt tablets.
In this hydration guide for cyclists we’ll cut through the noise, answering four specific questions:
- What’s the best strategy to stay optimally hydrated during exercise?
- When is drink mix a better option than water?
- Is there a benefit to supplementing with an electrolyte only product outside of exercise?
- Are salt tablets a good option in especially hot conditions?
Before we answer the above questions, let’s cover a few historical perspectives on hydration.
In The Beginning
Early hydration guidelines sought to minimize fluid loss by encouraging drinking as much water as possible [1]. Research showed a direct connection between fluid loss and a rise in core temperature. It also linked fluid loss to an increase in skin temperature and a drop in performance [2]. These findings led to the “drink to maximum tolerance” approach.
In short, when dehydration approaches a 2% or greater loss of total body mass, aerobic performance declines [3, 4]. The more you drink, the less fluid you lose, and supposedly, the better your performance.
Sounds simple, but the problem with “drink to maximum tolerance” is the risk of drinking too much. Too much water intake can lead to hyponatremia, a serious condition in which sodium levels in the blood are diluted causing sickness and even death [5, 6].
In simple terms, hyponatremia is a big problem that can crater your performance and even kill you.
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Let Thirst Be Your Guide
With hyponatremia as a backdrop, more recent guidelines have emphasized the individual nature of sweat rates and electrolyte concentration [7]. What’s the simplest way to respect a difference in hydration needs between cyclists? Tell them to drink when they’re thirsty and to leave the bottle in the cage when they’re not [8, 9].
“Drink to thirst” sounds good, but can still result in dehydration ranging from 1 to 3% of body weight [10]. Since performance may decline with as little as 1% loss in body weight [11], allowing thirst to be your guide might lead to a less-than-optimal hydration strategy.
Better To Make a Plan
More recently a new school of thought has emerged combining the “drink to tolerance” and “drink to thirst” approaches. It’s called “prescribed drinking” and aims to minimize fluid loss while steering clear of hyponatremia [12].
The first step in a “prescribed drinking approach” is to weigh yourself before and after a trial ride. After determining your fluid needs for an event, systematically “dose” fluid throughout a race, aiming for a total body weight loss of under .5% [12].
In a 2017 study, the “prescribed drinking approach” showed a performance advantage over that of “drinking to thirst”. This performance edge was hypothesized to come from “lower thermoregulatory strain and greater sweating response [12]”.
In short, “prescribed drinking” may help you find the goldilocks zone of an individualized hydration strategy.
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Hydration is Fake News
Before you draw out the perfect hydration strategy, several studies have made a compelling case that dehydration isn’t that big a deal after all.
In a landmark 2011 study, researchers showed an inverse relationship between percent of body weight loss and finishing times in a marathon. In other words, the fastest runners in the race were also the most dehydrated at the finish [13]. The results of this study seem to conflict with the accepted wisdom to minimize fluid loss as much as possible.
One possible reason for conflicting research around the significance of fluid loss is that previous studies overstated the negative impact of dehydration. Without outdoor wind speeds to mitigate core and skin temperature increases, the effect of dehydration might have been inflated in classic indoor, “laboratory-based” research [14].
Several other studies seem to confirm this point by showing no performance difference between cyclists who lost around 2% of their body weight as compared to cyclists only losing around .5% when trials were done outdoors [8].
Another possible explanation for the disconnect in hydration research comes down to the placebo effect. While previous participants drank water at various rates/quantities during their testing protocol, researchers in a 2015 study used intravenous infusion to blind participants to their hydration status [15].
You heard that right, during the testing protocol, each rider had an IV attached either hydrating with fluid, or doing nothing (leading to dehydration). This protocol enabled researchers to remove the placebo effect of expecting that drinking water and staying hydrated might result in improved performance.
What did researchers find? There was no performance difference between cyclists who were unknowingly hydrated (around .5% body weight loss) vs. those dehydrated (around 3.2% body weight loss) [15]. Hydration status didn’t seem to matter, leading some to question whether focusing so much on hydration is worth the trouble at all [14, 15].
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In Context
With historical context in place, let’s return to answering our first question:
Q: What’s the best strategy to stay optimally hydrated during exercise?
As you might have guessed, our answer begins with an unsatisfying “it depends”. Before we get to the “it depends” part, here’s one fundamental of every good hydration strategy.
Make sure to begin your ride or race fully hydrated. You can do this by ensuring your urine color is in the range of “very pale yellow to pale yellow” [17, 21]. Beginning from a “fully hydrated” state should be your baseline strategy for every ride or race you find yourself in.
Obviously, the more you sweat (either as a product of greater intensity or hotter weather) the more purposeful your hydration strategy should be: this is where “it depends” takes shape.
- For high intensity races under 1 hour, don’t worry about drinking much during the race [8]. Aim instead to swallow a bit of drink mix every 10m or so (we’ll get to why drink mix offers an advantage in a minute) [18].
- Since thirst is often an inaccurate indicator of hydration status, most long or intense riding scenarios are best served by some sort of “prescribed drinking” approach. Here are two “prescribed drinking” approaches of varying complexity:
- Take your pre/post ride weight, accounting for fluid consumed. Tally up how much fluid you lost. Use this as a baseline to plan out fluid needs to keep total body water loss to around 2% in your most important rides/races.
- Monitor your urine color at multiple points over a long ride. Are you able to stay in a “pale yellow to very pale yellow” range? If so, take note of the amount/frequency of fluid intake and try and replicate this on future rides.
Q: When is drink mix a better option than water?
If you’re riding intensely over several hours, or looking for a potential performance boost in a short race, a drink mix is your best bet.
In short races, it’s not the energy content of the drink that matters, but rather a performance boost that may occur when your brain perceives incoming carbohydrate in your mouth [18].
In most other riding scenarios drink mix offers an advantage to water, because it contains carbohydrate (along with sodium and other electrolytes).
A fluid solution with carbohydrate, hydrates you more rapidly than water alone while also providing an easy source of energy. Having said that, here are a few important caveats.
Too much carbohydrate in your bottle, can have the effect of dehydrating you by means of drawing fluid out of your blood plasma to aid in digestion of the carbohydrate in your small intestine [19].
The best concentration of carbohydrate to optimize hydration seems to be around 3-4%. This translates to about 30g of carbohydrate in a small cycling bottle. For a product like Skratch Hydration Mix this would be about 1 1/2 scoops per 22oz bottle of water.
For higher-carbohydrate drink mixes in your bottle, be aware that you’re making a trade-off to prioritize fueling over optimal hydration. This trade-off may or may not be smart depending on the ride intensity, duration, and access to other fluids during a race.
Take this spectrum of hydration-fueling into account when testing different products in your training. In general, the higher the concentration of carbohydrate in your bottle, the more water (or diluted drink mix) you’ll need to consume to limit fluid losses and optimize your hydration.
Ride Basic: A Minimalist Guide to Maximize Your Cycling
Whether you’re a beginner eager to complete your first fondo, or a seasoned pro aiming to refresh the foundational principles of long-term cycling success, this time-efficient guide offers invaluable insights into why and how you can Ride Basic.
Q: Is there a benefit to supplementing with an electrolyte only product outside of exercise?
Probably not. For most people, under most circumstances, your diet leading up to exercise, and your meals after exercise will provide plenty of sodium and electrolytes to replace what is lost in sweating [19].
Furthermore, the sodium and other electrolytes included in drink mix aren’t meant to replace the electrolytes lost in sweat, but instead to make drink mix more “palatable, maintain your thirst, prevent hyponatremia, improve the rate of hydration, and increase fluid retention” [19].
During exercise, electrolyte products may aid in improving your hydration and avoiding hyponatremia like mentioned above, but if you’re not exercising, then “drinking water to thirst” and eating a quality diet is a better/cheaper strategy than paying for an unnecessary electrolyte product.
In short, skip the electrolyte specific products and buy a drink mix or other carbohydrate rich food instead.
Q: Are salt tablets a good option in hot conditions?
In short, there is little evidence to suggest that supplementing with sodium (like a salt tablet) during exercise improves performance [20]. Here’s why [19]:
- You have sodium stores in your body that can be used during exercise.
- If you’re smartly utilizing a drink mix, you’re already getting additional sodium in addition to the performance benefit of carbohydrate.
- If you’re not over-drinking water (as discussed earlier), there’s little risk of developing hyponatremia: i.e., there’s no need to match your fluid intake with more sodium.
In Summary
- When you’re not exercising, a “drink to thirst” approach is fine. No need for additional electrolyte products, your diet will cover your sodium and electrolyte needs.
- Make sure to start each exercise session fully hydrated.
- Make sure you’re accounting for the fact that thirst is an unreliable proxy for your hydration status.
- Because thirst can be unreliable during exercise, develop your own systematic hydration strategy. Aim to limit fluid losses to less than 2% on training and race days.
P.S.
Does all this talk of hydration stress you out? Don’t worry about it. As long as you start your ride well hydrated and try to keep your pee pale yellow, you’ll probably be fine. Focus instead on smashing the pedals and crushing carbs.
References
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- Bardis, C.N., et al., Prescribed Drinking Leads to Better Cycling Performance than Ad Libitum Drinking. Med Sci Sports Exerc, 2017.
- Zouhal, H., et al., Inverse relationship between percentage body weight change and finishing time in 643 forty-two-kilometre marathon runners. Br J Sports Med, 2011. 45(14): p. 1101-5.
- Wall, B.A., et al., Current hydration guidelines are erroneous: dehydration does not impair exercise performance in the heat. Br J Sports Med, 2015. 49(16): p. 1077-83.
- Cheung, S.S., et al., Separate and combined effects of dehydration and thirst sensation on exercise performance in the heat. Scand J Med Sci Sports, 2015. 25 Suppl 1: p. 104-11.
- Casa, D.J., et al., Influence of hydration on physiological function and performance during trail running in the heat. J Athl Train, 2010. 45(2): p. 147-56.
- Armstrong, L.E., et al., Urinary indices during dehydration, exercise, and rehydration. Int J Sport Nutr, 1998. 8(4): p. 345-55.
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- Jeukendrup, A.E. and M. Gleeson, Sport nutrition. 2024.
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- Kostelnik SB, Davy KP, Hedrick VE, Thomas DT, Davy BM. The Validity of Urine Color as a Hydration Biomarker within the General Adult Population and Athletes: A Systematic Review. J Am Coll Nutr. 2021 Feb;40(2):172-179.
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