Hydration on a long ride

Hydration on a long ride

By Nick Kleban

What if I told you that you could ride faster, longer and harder just by drinking this one beverage? I’m sure you would be curious to know what it is, right? The answer is none other than the world’s most consumed beverage, water. 


So what’s the big deal? Everyone knows that you need to drink water to survive, just 3 days without it can be fatal, but how big an impact does just mild dehydration have on athletic performance? A 2013 study published in the Journal of Athletic Training tested the effects of mild dehydration for 10 well-trained endurance cyclists on a 5 kilometer hillclimb course. The subjects either started the course euhydrated or dehydrated by 1% of their body mass before beginning the effort. What the study found was that the hydrated cyclists completed the course 5.8% faster than the dehydrated athletes, had a lower core temperature immediately following the effort and additionally had lower Rate of Perceived Exertion (RPE) scores across the board. To put these numbers in perspective, 2019 Tour de France champion Egan Bernal won the edition of the race with a time of 82 hours and 57 minutes. Hypothetically, saying Bernal was consistently just 1% of body mass dehydrated like the study (assuming a decrease in speed by 5.8%), this would have tacked nearly an extra 5 hours onto his final race time; more than the difference between first and LAST in the general classification! 


Fluid Requirements 


So, yes, water is very important, and I’m sure many have heard the “you’re not drinking enough water” speal from our mothers, myself included, but how much exactly should we be drinking daily?


The National Academies of Sciences, Engineering, and Medicine determined that an adequate daily fluid intake is:

  • About 15.5 cups (3.7 liters) of fluids for men
  • About 11.5 cups (2.7 liters) of fluids a day for women

Granted about 20% of our fluid intake comes from food, this means we should be ideally drinking 12.4 cups (2.93 litres) for men and 9.2 cups (2.17 litres) for women not including the water depleted while exercising. 

On the bike, fluids are just as essential to performance. Given the typically steady-state nature of cycling (as opposed to sports such as basketball or soccer), it becomes quite simple to predict approximately how much water needs to be consumed to replenish fluids lost as sweat. This can be observed in the figure below: 

This chart gives a pretty detailed overview of the fluid needed to replenish during steady-state exercise. For example, as the graph shows, if 4 kg of body weight is lost as sweat, the individual would need about 2.7 litres of water to replenish the lost fluids. 

In simpler terms, the rule of thumb many cyclists go by is to drink one 500 ml bidon for every hour on the bike. Some other factors do play into this, such as your weight and the weather, which alone can push this figure closer to 1 L/ hour on hot summer days. I find it’s not practical to be able to drink a litre every hour (i.e it seems have my hands off the handlebars drinking more often than not plus that’s a lot of gas station stops), so instead, I try to drink 500-1000 L of sports drink (see the carbs section for more) in the hours leading up to a big ride to make sure I’m hydrated before even getting on the bike. 

For a long day on the bike or a multi stage event like Tour de France, where maintaining a good level of  hydration becomes more important, we can better pinpoint our individual hydration needs by weighing ourselves before and after a long ride. The difference between the 2 weights (minus the weight of any fluid drunk on the ride) is our total fluid loss.  By dividing that figure by the number of hours on the bike we can work out how many litres per hour we should drink.



Electrolytes are salts that include sodium, potassium, calcium and magnesium that are lost in sweat and are essential for normal cellular function, thus have to be replaced. According to the American College of Sports Medicine (ACSM), if your ride is less than four hours, you probably don’t need to supplement with electrolytes unless your jersey is caked with salt (we all have this friend) or you cramp easily. Sodium depletion may be one of the causes of cramps, so if you suffer from cramps, try supplementing with sodium and make a record of what you take to see if there is a consistent link.

If your ride is longer than four hours, then additional sodium and potassium are recommended. For this, the ACSM recommends 120-170 mg of sodium and 19-46 mg of potassium for each 8 fl oz (double for a 500 ml water bottle). Most sports drinks nowadays contain the correct balance of electrolytes, so it’s quite easy to hit these recommendations. 

So for those of you who xact nutrition’s electrolyte tablets, you might be wondering why they have a higher sodium level?

Research shows that fluids are better absorbed (reducing that sloshy feeling in the stomach) at around 1200 mg of sodium per litre (Sodium intake and post-exercise re-hydration in man, R. J. Maughan & J. B. Leiper, 1995).  So in times of need such as hot conditions and long endurance events (2 hrs +), where hydration is a priority, the XACT ELECTROLYTES tabs will respond to the athletes needs.

However, in real life, we often go for a mix of water in one bottle and electrolytes in the other, or a couple of cups of coke at the aid station, which dilutes our electrolyte to fluid ratio and therefore slows absorption.  Life is not always optimal but at least by having a high level of sodium in one of the bottles then it is helping more than an electrolyte drink with lower amounts, as it is the accumulation of fluids in the stomach that is important.



For longer rides, it makes sense to combine calorie intake with fluids, given that the guideline for appropriate carb fueling is approximately 1 gram of carbohydrate per kilogram of body weight per hour of riding (see our article all about carbs for more information on this). 500 ml of isotonic sports drink (see below) will contain usually between 30-40 g of carbohydrates which makes taking onboard the remaining portion of carbs relatively easy to satisfy this energy requirement. Most sports drinks contain a mix of simple sugars like glucose and fructose which are absorbed quickly to give more immediate energy as well as complex sugars like maltodextrin that provide longer term energy. 

As you dissolve your sports drink powder of choice into your water bottles before a ride, it’s important to consider how much you are putting into each bottle. The concentration (osmolarity) of the drink will drastically affect how your body will handle it. Blood typically has an osmolarity of 300mOs/kg so a solution with approximately equal osmolarity is said to be isotonic, with solutions less than or greater than being called hypotonic and hypertonic respectively. Below is a summary of how these different concentrations are utilised by the body during endurance exercise as described by nutrition specialist and triathlete, Juri Kaloc: 

  • Hypotonic drinks – These have a lower concentration of sugars (1 – 4%) than blood, that’s why they allow for very fast absorption. They are best used before or during long endurance events where hydration is the top priority.
  • Isotonic drinks – These have a similar concentration of sugars (6 – 8 %) as blood. They are the most universal when it comes to usage and that’s why most regular sports drinks use this formula. They give you a moderate amount of carbs and are absorbed relatively fast too, but can cause digestive issues in higher intensities.
  • Hypertonic drinks – These have a higher concentration of sugars (10 % +) than blood. They digest slowly so they aren’t good for consumption on the bike they would cause digestive issues. They are best used for recovery. 

Another way to achieve the isotonic ratio is to eat 1 XACT ENERGY fruit bar with your 500 ml of water.  The 30 g of carbs in the bar will mix with the water in your stomach and achieve the same the effect.

Bonus: Coffee 

Oh yes, how could I forget about a cyclist’s best friend, coffee. It’s hard to deny the benefits the stimulatory effects caffeine can have on performance, but also the not so great. For more information on this, I would recommend checking out Alister Gardner’s piece on Caffeine also found on our blog!


Bardis, C., Kavouras, S., Arnaoutis, G., Panagiotakos, D., & Sidossis, L. (2013). Mild dehydration and cycling performance during 5-kilometer hill climbing. Retrieved July 25, 2020, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3867084/

How long can you live without water? Facts and effects. (n.d.). Retrieved July 25, 2020, from https://www.medicalnewstoday.com/articles/325174

Hydration on the bike. (n.d.). Retrieved July 25, 2020, from https://www.britishcycling.org.uk/knowledge/nutrition/drinking-on-bike/article/izn20140514-Nutrition-Hydration-101-0

Irons, K., Marsh, J., MD, B., & Ford, K. (2018, April 01). What You Should Know About Electrolytes. Retrieved July 25, 2020, from https://www.roadbikerider.com/what-you-should-know-about-electrolytes-d3/

Kaloc, J. (2017, September 06). Cyclists and Hydration – Improve Your Performance. Retrieved July 25, 2020, from https://www.welovecycling.com/wide/2017/09/06/cyclists-hydration-improve-performance/

Official classifications of Tour de France 2020 - Stage 21. (n.d.). Retrieved July 25, 2020, from https://www.letour.fr/en/rankings

Water: How much should you drink every day? (2017, September 06). Retrieved July 25, 2020, from https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/water/art-20044256