Last week I discussed riding in the heat and hydration, using Mike as an example. Mike had raced three 12-hour races this spring. He successfully used his own homemade electrolyte drink in the third race and had no problems with cramps.
How much do you sweat?
On average, if you are riding in moderate conditions — that is, you aren’t gaining heat from the environment — each hour you’ll produce 600 to 800 ml (21 to 27 fl. oz.) of sweat!
Each hour you sweat out almost as much fluid as is contained in one standard (about 24 oz.) water bottle! If you push the pace a little, are climbing, are riding in hot weather or you are a larger rider, you could easily produce 32 fl. oz. (1 quart, or 1 liter) or more of sweat per hour.
Your personal sweat rate depends on: your fitness; how hard you are riding; the ambient conditions; and the variability among individuals.
Sodium is the primary electrolytes lost in sweat, along with some potassium. The others are lost in only trace amounts, and if you eat a balanced, well-rounded diet, then you have all the other electrolytes you need to ride in the heat.
Suppose you are sweating 700 ml (24 fl. oz.) per hour, containing an average amount of sodium, 560 mg. On a four-hour ride you would sweat out about 2,240 mg of sodium.
That sounds like a lot — it’s 50% more than the Daily Recommended Intake — but it’s only about 3% of your bodily stores!
How much electrolytes do you need?
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 or you cramp. Sodium depletion may be one of the causes of cramps, so if you suffer from cramps, try supplementing with sodium.
If your ride is longer than four hours, then additional sodium and potassium are recommended.
Electrolyte replacement drinks
Here’s what the ACSM recommends for a sports drink per 8 fl. oz.:
- Calories 48 – 96
- Sodium 120 – 170 mg
- Potassium 19 – 46 mg
Here’s Mike’s mix for a 20 fl. oz. bottle, “17 oz. water, 2 oz. coconut water, 1 oz. apple juice and ¼-teaspoon table salt. By my math, it almost exactly replicates the ideal balance of water, sodium and potassium, tastes OK, and is dirt-cheap compared to the sports formulae sold by sports nutrition companies.” Mike’s Homemade Mix is close to the ACSM recommendations on sodium and potassium but only has 7 calories / 8 fl. oz. He makes up for the low calories with food he eats.
Here’s my homemade sports drink to make 1 quart (0.95 L), which matches all of the ACSM’s recommendations:
- 1/4 cup (80 ml) orange juice
- 8 teaspoons (50 g) sucrose (table sugar), glucose or maltodextrin (a starch)
- 1/4 teaspoon (1.2 ml) salt
- water to make 1 quart (0.95 L)
Important: The three most popular sports drinks (Gatorade, Powerade, Heed) have much lower sodium and potassium than the ACSM’s recommendations. If they did have the recommended level of sodium, they wouldn’t be palatable. Just know that while these drinks may taste good (or at least OK), they don’t contain the ACSM-recommended amounts of the two key electrolytes.
Electrolyte replacement supplements
If you choose to use an electrolyte replacement supplement, check to see how much sodium and potassium it contains. One popular capsule contains only 40 mg of sodium and 80 mg of potassium, as well as other trace electrolytes, which you don’t need! To meet the ACSM’s recommended sodium intake, you’d need to take 3 to 4 capsuleswith every 24 fl. oz. bottle water that you drink.
Mike said, “At both Sebring and Bessie’s Creek 12-hour races, I started feeling on the edge of cramping around mile 200 and had to back off of power for a little while until that went away. With the mix (oh yeah, and another two months’ training!), I had zero sensation of pending cramps at the Maryland race.”
Sodium depletion may be one of the two primary causes of muscle cramps. If you are prone to cramps, start supplementing with sodium early in the ride. (The other primary cause is neuromuscular fatigue.)
Dehydration doesn’t cause cramps. Pro riders often get dehydrated but rarely cramp. Lilian Calmejane, who won stage 8 of the Tour de France, did suffer from cramps. It was a blazingly fast stage, and his cramps probably were due to neuromuscular fatigue.
Update on acclimatization
In a recent study, scientists tested a simple acclimatization method on nine recreational runners who were not heat-acclimated. The subjects included one woman. The scientists turned up the heat to about 90 degrees (32 degrees Celsius). The runners then ran a simulated 5-kilometer race on a treadmill in the sweltering room.
Then the scientists began acclimating them to the heat. They turned up the heat in the lab to almost 99 degrees (37 degrees Celsius) and the volunteers pedaled an exercise bicycle for about 90 minutes in this heat, at an increasingly vigorous pace for five days in a row, under the close supervision of the researchers.
Afterward, the runners repeated their 5K-treadmill race. After acclimating, the runners dropped their average time by more than 6.5 percent compared to their first run!
The research conclusions are similar to Cutting Edge Cycling, which says that to acclimate you need to exercise hard enough that you are sweating heavily for 60 – 90 minutes for 4 to 8 sessions. The fitter you are, the fewer sessions that you need. It notes that passive acclimatization, like sitting in a sauna or hot tub for 60 – 90 minutes, may provide the same benefits … but that’s 60 – 90 minutes you aren’t training!
You can learn more about the science of riding in the heat, and managing your fluids and electrolytes, in my two-eArticle Cycling in the Heat Bundle.
- Cycling in the Heat, Part 1: Ride Management is 19 pages and covers how to acclimate to hot conditions, how to train in hot months, what to wear, eat and drink, how to cool down if you overheat, and how to deal with heat-related problems.
- Cycling in the Heat, Part 2: Hydration Management is 21 pages and covers how to determine how much you should drink depending on your physiology and sweat rate, how best to replace your fluids and electrolytes, the contents of different sports drinks, how to make your own electrolyte replacement drinks, how to rehydrate after a ride, and how to deal with hydration-related problems.
Cycling in the Heat Parts 1 and 2 is just $8.98 (a 10% savings) and, as always, just $7.64 for our Premium Members (includes their everyday 15% discount!).
My Summer Riding bundle contains both of the Cycling in the Heat articles as well as articles on handling cramps and learning the nutrition and hydration secrets of the pros:
- Cycling in the Heat, Part 1: Ride Management, 19 pages
- Cycling in the Heat, Part 2:Hydration Management, 21 pages
- Preventing and Treating Cramps: The 10 pages give you a detailed look into the causes of cramps so that you can understand and implement prevention techniques. It provides tips (both on-bike and off-bike, including photos) for breaking and flushing cramps.
- Eating and Drinking Like the Pros: The 14 pages are based on research about what pro riders consume before, during and after a stage. The findings hold lessons and benefits for cyclists at all levels. Eating and drinking like the pros offers recreational riders the same nutritional benefits, which you can customize to your own needs – typically at a fraction of the cost of commercial sports food and drink, if you choose to make your own. I worked with a professor of nutrition and an expert on hydration and electrolytes (both experts are cyclists) in creating recipes for both sports drinks and food.
The Summer Riding bundle is just $15.96 (a $4 savings) and, as always, just $13.58 for our Premium Members (includes their everyday 15% discount!).
Kerry Irons says
Electrolyte needs vary widely from person to person. I remember a study reported by Monique Ryan in VeloNews that sodium losses per liter of sweat have been measured from 115 to 2300 mg. Studies on football players have shown that players who lost more Na were more likely to cramp. So riders who want to be comfortable riding in high teat/humidity conditions need to learn their own needs through experimentation. Relying on a single number may result in significant sodium deficit if you are a “salty sweater.”
John Marsh says
Kerry, you’re absolutely right. Coach Hughes made sure to state the numbers he referred to as an average. He followed that up with:
“Your personal sweat rate depends on: your fitness; how hard you are riding; the ambient conditions; and the variability among individuals.”
I’ve always lived in hot, very humid climates, and I think I’ve become somewhat acclimated to that type of weather. Even when the temperature in the morning is in the 70s (it rarely gets any cooler in much of the South in the summer), the humidity is often near 90%. So you simply sweat profusely, no matter what.
You definitely need to figure out how to deal with your own very specific body and all the conditions in which you’re riding. As Coach Hughes also often says: “You’re an experiment of one.”
bernard Burton MD says
Another consideration on electrolyte loss is chronic calcium deficiency due to frequent prolonged exercise in hot and humid conditions. In two hours it is possible to deplete 2000 mg of calcium in some people, the most that is usually replaceable in a day. More sweating could cause a chronic calcium deficiency, increasing the risk of bone loss( osteopenia or osteoporosis ). Attention to calcium intake and vit.D intake is encouraged.
Katie Ford says
I think this is a really interesting article, but hasn’t really addressed the other side of the hydration coin, which is the far more dangerous over-hydration. I’d be interested in hearing thoughts on a very small percentage dehydrated state below that of perfect hydration. It’s certainly my preference, given the effects of Hyponatremia and the secondary issues it can cause, cramp seems far more preferable as a side effect and much easier to know that hydration action is required, rather than the far less easy to spot indicators of over-hydration. Protein shakes as well as simply electrolyte supplemented drinking also seems to have a very positive effect on performance and an overall hydration strategy too.
Jess Rainer says
Good article and helpful. But the comment about popular sports drinks is not accurate. You state, “the three most popular sports drinks (Gatorade, Powerade, Heed) have much lower sodium and potassium than the ACSM’s recommendations.” However, I researched the Nutrition Facts on Gatorade and it DOES meet the ACSM recommendation for potassium (just about mid center in the range). And while Gatorade does fall short on the ACSM recommended amount of sodium, it is only 11% down which is not what I would interpret as “much lower” as stated in the article. That amount of sodium can easily be made up by the other food, drinks or supplements riders may consume before or during the ride. Below is a chart showing the ACSM recommendations for a sports drink per 8 fl. oz. and how Gatorade stacks up:
Calories: ACSM: 48 – 96 Gatorade: 53
Sodium: ACSM: 120 – 170 mg Gatorade: 106.4 mg
Potassium: ACSM: 19 – 46 mg Gatorade: 33.3 mg
So Gatorade meets 2 of the recommendations and misses the other one by only 11%. Not bad. Much better than I expected!