By Coach John Hughes

It was 95F (35C) and sweat was dripping into my eyes, so I tied a bandana around my head and put my cowboy hat back on. My wife and I were sitting in the sun listening to Yonder Mountain String Band’s Sunday morning gospel set at RockyGrass, the annual bluegrass festival only a few miles from our house in Boulder, Colorado. Yonder usually plays amphitheaters seating 10,000 or more. We were lucky that they were playing to an audience of only about a thousand at Planet Bluegrass on the banks of the South St. Vrain river, a popular spot for soaking to escape the heat!

Riding in that sun I would have also been hot, primarily because exercise produces heat. The human engine is only about 30 percent efficient; meaning that for the 500 calories I’d burn in an hour of riding, only about 150 calories would provide forward motion and the other 350 calories would produce heat! But when riding I would have moving air to help cool me a bit — just sitting in the sun listening to music definitely felt hotter!

It's been – and continues to be – a blazing hot summer across much of North America. In fact, NASA announced recently that the first six months of 2016 were the hottest ever recorded. Temperatures were 2.4 degrees Fahrenheit higher than average between January and June this year, compared to the late 19th century. Earth has now had 14 months in a row of the hottest temperatures seen since records began to be kept in 1880, according to the U.S. National Oceanic and Atmospheric Administration. Of course, we've all continued to ride, haven't we?

No matter what you're doing outside in the heat, knowing how to properly stay hydrated and replenishing the vital electrolytes you need is growing in importance.

Sodium is key in replenishing electroylytes

I drank a liter or more of water every hour as I sat there sweating and enjoying the music. What did I do for electrolytes? For lunch I had a sandwich of deli turkey, a dill pickle and tomato juice, which contained the following amounts of sodium:

  • 1,152 mg sodium from four ounces of turkey
  • 1,181 mg of sodium from a 4-inch dill pickle
  • 1,306 mg of sodium from 16 ounces of tomato juice
  • That comes to 3,639 total mg of sodium

Why so much sodium? Because that’s the most significant electrolyte lost in sweat. Take a look at the following table.

Electrolyte Concentration per Liter (Quart) of Sweat

Electrolyte Concentration / Liter (quart) Daily Recommended Intake (DRI) Daily Recommended for Athletes
Sodium 800 mg 1,500 mg >1,500 mg up to 10 g
Chloride 1,065 mg 2,300 mg >2,300 mg to match sweat losses
Potassium 115 mg 4,700 mg 4,700 mg or more with heavy sweat losses
Calcium 40 mg 1,000 mg 1,300 – 1,500 mg
Magnesium 19 mg

Males 420 mg

Females 320 mg

400 – 450 mg if from food

350 mg if from supplements

(Benardot, Dan, Ph. D, RD. (2012) Advanced Sports Nutrition, 2nd ed. Human Kinetics, Champaign, IL)

The amounts of sodium and chloride in a liter of sweat greatly exceeds the amounts in my daily diet, while the amounts of potassium, calcium and magnesium in a liter of sweat are pretty small compared to what I should be consuming every day. The sodium, of course, comes from added salt in different foods, which also provides the necessary chloride.

My lunch also gave me plenty of potassium:

  • 342 mg potassium from four ounces of turkey
  • 242 mg of potassium from a 4-inch dill pickle
  • 1,132 mg of potassium from eight ounces of tomato juice
  • 1,716 total mg of potassium

As an alternative, I could have eaten four medium bananas to get the same amount of potassium, but not much sodium.

During the day I also snacked on pretzels. One ounce of salted hard pretzels contains 385 mg of sodium and 51 mg of potassium but only 0.7 grams of fat, unlike chips, which have a lot of fat. Of course, that one ounce of pretzels also has 108 calories, so I didn’t munch down a whole bag!

Most Western diets provide more sodium than is generally healthy. Commercially canned foods and many other processed foods have a lot of added sodium, as do fast food and restaurant meals. My daily diet avoids all of these, but when riding on hot days I use my salt shaker at the table!

Trace electrolytes can play a role in cramping

According to my health care provider Kaiser Permanente, these are good sources of the trace electrolytes:

Mineral Function Sources
Potassium Needed for proper fluid balance, nerve transmission, and muscle contraction Meats, milk, fresh fruits and vegetables, whole grains, legumes
Calcium Important for healthy bones and teeth; helps muscles relax and contract; important in nerve functioning, blood clotting, blood pressure regulation, immune system health Milk and milk products; canned fish with bones (salmon, sardines); fortified tofu and fortified soy milk; greens (broccoli, mustard greens); legumes
Magnesium Found in bones; needed for making protein, muscle contraction, nerve transmission, immune system health Nuts and seeds; legumes; leafy, green vegetables; seafood; chocolate; artichokes; "hard" drinking water

Note that potassium, calcium and magnesium all play a role in nerve transmission and muscle contraction, and a significant deficiency of one of these may play a role in cramping. If you eat enough of these foods daily, then the amounts of these trace electrolytes lost in sweat won’t cause cramping; however, if you have a dietary deficiency then one of these could have a role in cramping.

On a ride, what are your sources of electrolytes? If you use a sports drink or an electrolyte replacement pill, how much would you need to consume to equal the amount of sodium in a liter of sweat? Or of potassium in a liter of sweat? Most of the so-called sports drinks (electrolyte replacement drinks) don’t have enough of either. Why not? Because they wouldn’t taste good and you wouldn’t spend your money on them!

Warning: too much magnesium can cause diarrhea, so check the magnesium content of your electrolyte supplement so you don’t exceed the Daily Recommended Intake!

In the June 30 RBR Newsletter I gave you my recipe for a home-made sports drink that does provide the electrolytes you need and is a lot cheaper!


RoadBikeRider podcasts on heat and hydration

Coach John Hughes joined host George Thomas for these recent podcasts:


Additional Sources of Heat-Riding Information

My four-article cost-saving Summer Riding Bundle gives you the info you need to ride better and more comfortably. It includes:

  • Cycling in the Heat, Part 1: Ride Management. 20 pages on how to acclimate, how to ride in the heat without overheating, how to stay (relatively) cool, what to wear, what to eat and drink, how to cool down if you overheat and heat related problems
  • Cycling in the Heat, Part 2: Hydration Management. 21 pages on assessing your personal sweat rate and composition, how much you should drink, electrolyte replacement and the pros and cons of electrolyte replacement drinks, supplements and foods.
  • Preventing and Treating Cramps. I haven’t cramped in decades. 10 pages on what causes cramps, how to prevent them and what to do to break a cramp so you can keep riding.
  • Eating and Drinking Like the Pros: How to Make Your Own Sports Food and Drink — Nutritional Insight from Pro Teams. 15 pages covering what the pros eat and drink, what you can learn from this, how to make your own sports drinks, gels and solid food and what to eat at a minimart.

All this great info for only $15.96. Only $13.57 for our Premium Members with your 15% discount.


Coach John Hughes earned coaching certifications from USA Cycling and the National Strength and Conditioning Association. John’s cycling career includes course records in the Boston-Montreal-Boston 1200-km randonnée and the Furnace Creek 508, a Race Across AMerica (RAAM) qualifier. He has ridden solo RAAM twice and is a 5-time finisher of the 1200-km Paris-Brest-Paris. He has written nearly 30 eBooks and eArticles on cycling training and nutrition, available in RBR’s eBookstore at Coach John Hughes. Click to read John's full bio.

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