Even in very hot conditions, most of the heat is generated by your body, which is only about 25% efficient. For every four calories you burn, only one calorie provides energy to move you forward—and the other three calories produce heat. That heat must be dissipated from your body through primarily by sweat. Your body is like a car’s radiator. Blood circulates through your core, heats up and circulates to the skin where heat is dissipated via sweat.
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 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 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.
Electrolyte Concentration per Liter (Quart) of Sweat
On average here’s what is in a liter or quart of sweat:
- Sodium: 800 mg / Liter (Quart)
- Chloride 1,065 mg
- Potassium 115 mg
- Calcium 40 mg
- Magnesium 19 mg
Daily Recommended Intake (DRI)
Let’s compare the amounts of the different electrolytes in sweat to the DRI:
- Sodium: DRI 1,500 mg or for athletes >1,500 mg up to 10g. Good sources of sodium include table salt, tomato & vegetable juice, pretzels, crackers, beef jerky, deli meat, cheese, dill pickles, pizza, soups, pasta sauces, canned vegetables, most fast food.
- Chloride: DRI 2,300 mg or for athletes >2,300 mg to match sweat losses. Good sources are the same as for sodium.
- Potassium: 4,700 mg or for athletes 4,700 mg or more with heavy sweat losses. Good sources include dairy (white & chocolate milk, yogurt), fruit (banana, pear, orange & orange juice, raisins, cantaloupe), vegetables (baked white & sweet potato, tomato & vegetable juice, corn, zucchini, avocado, carrots), dark chocolate.
- Calcium: 1,000 mg or for athletes 1,300 – 1,500 mg. Good sources include dairy (milk, yogurt, cheese, cottage cheese), dark leafy greens (spinach, kale, turnips, and collard greens, fortified cereals (Total, Raisin Bran, Corn Flakes), fortified orange juice, enriched breads, grains, and waffles
- Magnesium: males 420 mg, females 320 mg or for athletes 400 – 450 mg if from food or 350 mg if from supplements. Good sources include dark leafy greens (spinach, kale, Swiss chard), nuts (squash & pumpkin seeds, sesame seeds, Brazil nuts, almonds, cashews, mixed nuts), fish (halibut, mackerel, turbot), beans, banana, brown rice, quinoa, avocado, dried fruit (figs, prunes).
(Benardot, Dan, Ph. D, RD. (2012) Advanced Sports Nutrition, 2nd ed. Human Kinetics, Champaign, IL)
Note that a liter of sweat contains only 2.5% of the recommended intake of potassium, 4% of the recommended intake of calcium and magnesium only 4.5 – 6% of the recommended intake of magnesium.
Unless your diet is terrible or you are doing an ultra event sodium and chloride and perhaps potassium are the only electrolytes you really need.
Aren’t Electrolytes Important to Prevent Cramps?
Scientists have two general theories:
- Neuromuscular fatigue meaning that after all of those contractions your nerves fatigue. They send signals to the muscles that because of fatigue the muscles are at risk of injury and that the muscles should just contract and freeze to protect them from injury, i.e., you cramp.
- Sodium depletion
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 are several representative examples of commercial drinks. If your drink isn’t here read the label on the bottle. Per 8 fl. oz. (same size as ASCM recommendation)
- Gatorade – 50 calories, 110 mg sodium, 25 mg potassium – 7 servings to equal sodium lost in 1 qt. of sweat
- Powerade – 56 calories, 100 mg sodium, 30 mg potassium – 8 servings to equal sodium lost in 1 qt. of sweat.
- Heed – 104 calories, 40 mg sodium, 25 mg potassium – 20 servings to equal sodium lost in 1 qt. of sweat
- Skratch – 40 calories, 140 mg sodium, 20 mg potassium – 6 servings to equal sodium lost in 1 qt. of sweat
A few alternatives from the mini-mart:
- V-8 – 50 calories, 420 mg sodium, 470 mg potassium – 2 servings to equal sodium lost in 1 qt. of sweat.
- Low-fat milk – 100 calories, 125 mg sodium, 470 mg potassium – 6 servings to equal sodium lost in 1 qt. sweat
- Low-fat chocolate milk – 160 calories, 380 mg sodium, 425 mg potassium – 2 servings to equal sodium lost in 1 qt. of sweat
Sports drinks are deficient in sodium. If you choose to drink one because it provides calories, you like the taste and it’s convenient, then on rides over four hours (and shorter rides if you’re prone to cramping) you should supplement it to obtain more sodium.
Supplements, including electrolyte supplements, are a multi-million dollar business. However, the body absorbs minerals much more readily from food than from pills. For example, certain forms of calcium can only be absorbed with food. In general, if your diet provides sufficient minerals, then you don’t need to take supplements. If you choose to use a supplement, look for one with high sodium content, since that is the primary mineral lost in sweat.
Here are several representative examples of commercial drinks. If your supplement isn’t here read the label on the bottle. Per tablet
- Nuun – 360 mg sodium, 100 mg potassium – 2 tablets to equal sodium lost in 1 qt. of sweat
- Succeed S caps – 341 mg sodium, 21 mg potassium – 2 tablets to equal sodium lost in 1 qt. of sweat
- Endurolytes – 40 mg sodium, 25 mg potassium – 20 tablets to equal sodium lost in 1 qt. of sweat.
- Endurolytes Extreme – 120 mg sodium, 75 mg potassium – 7 tablets to equal sodium lost in 1 qt. of sweat
- Thermotabs salt tablets – 184 mg sodium, no potassium – 4 tablets to equal sodium lost in 1 qt. of sweat.
A few alternatives from the mini-mart:
- Subway 6” turkey sandwich – 280 calories, 760 mg sodium, no potassium
- Pretzels, 1 oz. 90 calories, 385 mg sodium, 41 mg potassium
- Wheat Thins, 1 oz. – 127 calories, 225 mg sodium, 59 mg potassium
When you’re shopping at a mini-mart read the label to see if it has what you need.
A Better Solution
Here’s the homemade sports drink I use, which meets the ACSM recommendations. Many of my clients have used this successfully. To make 1 quart:
- 1/3 cup (80 ml) orange juice
- 12 teaspoons sugar (adjust to taste)
- ¼ teaspoon salt
- Water to make 1 qt.
8 fl. oz. provides 100 calories, 300 mg sodium, 80 mg potassium. One quart makes four 8 fl. oz. servings.
(Yes, REALLY 12 teaspoons of sugar per quart. A single 12 ounce can of Coke has 9.75 teaspoons of sugar, for comparison.)
More Information on Riding in the Heat:
Get my 2-article bundle Cycling in the Heat
- Part one – Ride Management (20 pages) covers the effects of overheating, how to acclimate, now to train in hot months, what to wear in the heat, what to eat and drink in the heat, how to cool down if you overheat and heat-related problems.
- Part two – Hydration Management (21 pages) covers how to develop a personal hydration plan including assessing your sweat rate and how much you should drink, more on different types of electrolyte replacement and hydration related problems. The 41-page Cycling in the Heat bundle is $8.98.