Not sure how much sodium you need when cycling? This practical guide explains sweat loss, hydration and when electrolyte or sodium bicarbonate strategies may help.
Sodium needs during cycling vary widely because sweat rate and sweat-sodium concentration differ from rider to rider. Most endurance cyclists can start with general sodium guidelines, then adjust intake based on sweat loss, ride duration, weather conditions and personal experience.
The article also explains how to estimate sweat rate, when electrolyte replacement becomes more important on longer rides, and why sodium bicarbonate is not considered beneficial for steady endurance performance.
When we sweat, our bodies release water, electrolytes and other trace minerals and waste products. Proper hydration requires replacing the water and electrolytes lost through sweat.
The amount and composition of sweat varies drastically between individuals, with studies showing as much as a 10× difference in sweat rate and a 5× difference in sweat electrolyte concentration. It also varies from day to day for the same person.
Given this variability, it’s not possible to make broad recommendations for sodium intake while cycling.
It is possible, however, to estimate your needs so you can hydrate properly.
In this guide, we’ll explain the science of sweating and hydration and give you the information you need to estimate your sodium needs when cycling.
For the average cyclist (or any endurance athlete), the American College of Sports Medicine (ACSM) recommends consuming 300-600mg of sodium per hour, the equivalent of 0.75-1.5g of salt. Salt is 60% chloride and 40% sodium, both of which are lost through sweat and need to be replaced.
The exact amount of sodium required by an individual depends on their sweat rate (measured in litres per hour) and the electrolyte concentration of the sweat (measured in mmol of sodium and chloride per litre). We’ll explain how to estimate yours later.
Studies of athlete sweat rates suggest a typical range of 0.5-2L per hour of activity, though approximately 2 percent of athletes lose 3L or more per hour. Research on sweat electrolyte concentration demonstrates even greater variation, with one study showing sodium losses (in mg/L) ranging from 200mg/L to 2,300mg/L, with the average around 950mg/L.
In the study mentioned above, the researchers tested athletes from five team sports: Baseball, American football, rugby, football, and basketball. The average sodium loss for the 696 athletes was around 950mg/L with a range of 200-2300mg/L.
The 157 marathoners in another study have a similar average of 990mg/L, and a range of 161–2,197 mg/L. It’s likely that, on average, cyclists have sweat rates comparable to those of runners, given the high cardiovascular demands of both endurance sports.
Again, the variation between two individuals could be so great that these numbers provide little value.
However, with an understanding of these ranges, if you’re an experienced cyclist, you can likely make an informed guess as to where you fall within the range.
This ability of experienced athletes to make an informed guess was demonstrated in the study on the 696 athletes. They were asked in a survey where they think they fall in terms of the saltiness of their sweat, and, according to Precision Fuel and Hydration Founder and researcher on the study, Andy Bow, there’s “a strong correlation between how much sodium the athletes think they lose in their sweat and their actual sweat sodium concentration.”
Many factors influence why one cyclist loses more sodium than another; some are genetic, and others are related to training or heat acclimation.
If we are to imagine two riders completing an hour-long ride at the same relative effort, for example, their FTP, in identical conditions, the difference in sweat rate could be 10-fold, and the difference in sweat sodium concentration could be five-fold.
Aside from individual genetic factors, both sweat rate and sweat sodium concentration can, to a small degree, be trained.
The amount of sweat lost per hour of exercise increases with heat training. In as little as three days, the body starts adapting or “acclimating” to the hot temperatures by sweating earlier and in higher quantities, helping to regulate your core temperature. Sweat evaporating from the skin to cool the body is its primary function.
In addition to sweat-rate adaptations, research published in the Journal of Thermal Biology has found that training in the heat can reduce sweat sodium concentration by 30 to 60 percent.
Another important factor in sweat rate is biological sex.
On average, males may excrete more sodium per litre of sweat than females, with the females in this study demonstrating lower sweat sodium concentrations than the men.
By using the averages from the studies referenced above, it’s possible to calculate how much sodium a hypothetical “average athlete” would lose in 30 minutes of moderate cycling.
First, calculate the fluid loss for the 30-minute session: 1L/hr × 0.5 hours = 0.5L of sweat lost.
Next, multiply that fluid loss by the estimated sweat sodium concentration: 0.5L × 950mg/L = 475mg of sodium lost in 30 minutes.
From this calculation, it is easy to see how sodium needs can compound over longer-duration activities; for example, on a three-hour ride, this would put this athlete’s total sodium losses at 2,850mg (6 × 475mg).
To further illustrate this, if you’re a very salty sweater or have a high sweat rate, you could easily require over 5,000mg of sodium for the same three-hour ride.
To calculate your sodium needs for endurance rides, you can follow the steps below. On rides shorter than two hours, if you start properly hydrated, it’s not necessary to consume electrolytes, unless it’s a very hot, humid day and you’re riding at a high intensity.
Without a proper sweat sodium concentration test, remember that your calculation is only a rough estimate. The calculation is:
Firstly, you must estimate your sweat rate in litres per hour using the following steps, which the authors of this study deem the “simplest and most accurate” method.
To do so, you’ll need a scale with a measurement precision of at least 0.10kg, a digital food scale to measure the fluids you will consume during the test, and a towel. If you need to urinate, do so before weighing yourself, or else hold it until after the test.
Weigh yourself completely naked, then weigh the exact amount of water you will consume during the ride, or – to simplify – do not consume any water. Record both of these numbers. For example, 72kg and 500ml (500g) of water.
Complete a one-hour ride at your targeted endurance intensity on your indoor trainer or outdoors. If the outdoor temperature is very cold, this test is best performed indoors.
Dry yourself with the towel, and weigh yourself fully naked. If you have any water left, weigh it and subtract it from the pre-ride amount. Let’s say you weigh in at 70.4kg and you finish the water.
Subtract your pre-ride weight from the post-ride weight, and account for the water you consumed:
72 - 70.4 = 1.6kg
1.6kg - 500g = 1.1L/hour
Next, you need to test or estimate your sweat sodium concentration. For this example, let’s say you think your sweat sodium concentration is slightly above the 950mg/L average, at 1,050mg/L.
Multiply your sweat rate of 1.1L/hour × your sweat sodium concentration of 1,050mg/L.
When calculating how much sodium you need to replace while exercising, it’s important to consider how much water you’re consuming. Calculating the exact amount is a complex formula beyond the scope of this.
However, as this study on sodium requirements points out, if you are consuming more fluids (replacing a higher percentage of your fluid losses), you need more sodium. If you’re consuming less fluid, you can consume less sodium during exercise.
With some experience, you can figure out your rough electrolyte needs by noting how you felt during or after a ride. If you plan a ride similar to one you’ve done previously that ended with a headache or cramps, you probably need to increase your sodium intake slightly during the upcoming ride.
Existing options include completing a professional sweat test, using a wearable sensor such as Nix’s Sweat Patch, or making an educated guess at your sweat rate by taking the average and adjusting it based on your experience of your own body.
Precision Fuel & Hydration’s founder, Andy Blow, outlines the questions you need to ask yourself to make this estimate:
If you answer yes to several of these questions despite consuming some electrolytes during exercise, it is likely due to having a higher-than-average sweat sodium concentration.
Research shows that the amount of sodium an athlete requires during exercise depends on both the percentage of fluid losses that are replaced and the sodium concentration of the sweat.
To illustrate, if you replace 50 percent of the fluids you’ve lost, you’ll need less sodium than if you were to replace 80 percent of the fluids you’ve lost.
There’s no need to replace sodium during short rides. With regular water consumption and good nutrition pre and post-ride, you can replace any fluid and sodium losses.
The Australian Sports Commission states that it doesn’t appear necessary to have a targeted sodium-replacement strategy for medium-duration rides. However, if you’re a very salty sweater, have a high sweat rate, or are exercising in hot, humid conditions without being acclimatized, this review in the International Journal of Environmental Research and Public Health says that endurance athletes should consume around 300-600mg per hour of sodium or 500-700mg per litre of fluids.
During long rides of 3+ hours, a dedicated sodium-replacement strategy is required. It’s important to know if you’re a salty sweater or have a high sweat rate because the variation between individuals is so high that blanket recommendations have little value.
Nonetheless, a starting point that can be adjusted based on your experience is as stated above and stated by the American College of Sports Medicine (ACSM): 300-600mg per hour or 500-700mg per litre of fluid.
Finally, it’s important to remember that the food you consume on long rides also contributes to your sodium intake.
Sodium bicarbonate, also known as baking soda, is used in sports as a performance-enhancing (ergogenic) supplement. The form taken in sports is a highly concentrated version of household baking soda.
The International Society of Sports Nutrition’s position stand admits that the “ergogenic mechanisms of sodium bicarbonate are not yet fully understood.” However, they state that literature on the supplement shows that taking doses of 0.2-0.5 g/kg “improves performance in muscular endurance activities” of “high-intensity that last between 30 seconds and 12 minutes.”
They conclude, however, that though sodium bicarbonate improves exercise performance, “a portion of the ergogenic effect of sodium bicarbonate seems to be placebo-driven.”
The current understanding of research on sodium bicarbonate is that it does not improve endurance cycling performance, with the International Society of Sports Nutrition concluding that benefits are only observed for high-intensity efforts of up to 12 minutes.
The difference between taking sodium bicarbonate and consuming sodium while exercising is that consuming sodium or salt (sodium chloride) is necessary to replace the electrolytes that your body sheds through sweating, whereas sodium bicarb is a supplement that can improve performance in short, high-intensity efforts (30 seconds to 12 minutes).
Consuming sodium in the correct amount during long-duration exercise prevents dehydration, but consuming sodium bicarbonate doesn’t.
The most common mistakes that cyclists make in relation to sodium intake are the following:
1. Drinking plain water only
Hydrating only with plain water over the course of a long ride will dilute the amount of sodium in your bloodstream and cause hyponatremia, which is when blood sodium levels fall below a certain level.
According to the Mayo Clinic, some of the symptoms of hyponatremia may include:
For this reason, the ACSM recommends 500-700mg of sodium per litre of fluid consumed on rides longer than 3 hours.
2. Copying another person’s numbers
As we’ve seen throughout this article, there’s such enormous variability in sweat rate, and sweat-sodium concentration between individuals that what works for one person may be harmful for another.
If you’re a rider who naturally loses a lot of sodium in your sweat and sweat heavily, following guidelines for the average person could result in hyponatremia.
3. Confusing cramps with sodium depletion
Severe sodium depletion can contribute to cramping, but one study in the Journal of Strength and Conditioning Research states that “fluid and electrolyte losses may not be the sole cause.” Further research highlights that it’s “unlikely that a single factor (for example dehydration, electrolyte imbalance, or neuromuscular factors) is responsible for causing [exercise-associated muscle cramps] directly.”
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