Nutrition Essentials for Endurance Training

There are three essentials to nutrition when it comes to long distance training and racing. Liquids, calories, and sodium/electrolytes. If you lack in any one, youíll suffer. However, over the past few years the market has become saturated with products, all of them screaming that you need it now, and resulting in abundant confusion on what is and isnít necessary.

In this article I will try to help you wade through some of the marketing hype and distill the facts, as they are.

First, letís talk about liquids. When you exercise, you sweat, right? Your sweat is made up of water and electrolytes-salts (weíll get to that next). You sweat in order to keep your temperature down (heat loss through evaporation). If you want to keep exercising at a level commensurate with your athletic ability, you need to replace that water (and sodium) as well as you can. Otherwise, you will get dehydrated. When you are dehydrated your core temperature will rise, your heart rate will increase, and your heartís pumping ability will decrease. All this means that your muscles get less oxygen, you overheat, and you slow down.

Your sweat rate may vary, but it is probably in the 1 liter (33 ounces or 2 pounds) to 2 liter per hour range depending on your physiology and the environment. Thatís roughly 2-4 sports bottles of fluid per hour.

Salt, potassium, electrolytes: Your body needs salt and potassium to function properly. They are essential for nerve functions, muscle contraction, and water balance. A normal human being weighing 150 pounds has about 95 grams (9,500 mg) of salt in their body, and about double that amount of potassium. When we sweat, the average athlete loses somewhere around 200-400 milligrams per hour of both sodium and potassium. Since these electrolytes are essential for your nerve functions and muscle contractions, too little and youíll be unable to move as well and quickly as youíd like. Most sports drinks contain a mix of sodium and potassium, which work together. Note that since you have more potassium stored in your body, itís not as crucial to replace as sodium (and can be tough on the stomach in high concentrations).

What you need to avoid is going crazy with your sodium replacement plan. You donít need to take in 800mg of sodium per hour just because the product label says so. You need to determine what your sodium loss rate is, since everyoneís is specific to them. Some folks might lose more than 1000mg an hour, while others lose only 100mg.

Too much sodium ingested during exercise can result in cramps, diarrhea, swollen hands & feet due to fluid retention, and muscle spasms. All of these are bound to slow you down.

Too little sodium can result in a state called hypnotraemia. This is a dangerous chemical imbalance (low sodium levels in the blood) caused by overconsumption of fluid with inadequate sodium replacement. It can kill you.

The message here is to drink sports drinks during exercise lasting longer than 2-3hrs. You will need to experiment with long training days, different sports drinks, and sodium intake to discover your sodium requirements and favorite products if youíre training for half-IM and IM. If youíre training for sprints (<1.5hrs), salt replacement is a complete non-issue!

Calories. Carbs. Carbs carbs carbs carbs carbs carbs carbs. Atkins was mad. A gram of carbohydrate = 4 calories. Most folks will need somewhere between 30-60 grams of carbs per hour of exercise. Long distance athletes will want to replace on the high side. You need the carbs because your body only has around 1200-1500 calories stored in the form of muscle and liver glycogen. While you will burn a lot of stored fat during long distance exercise, other crucial sources are muscle glycogen and what you take in during exercise. Thus, eat or drink your carbs, keep your muscle glycogen levels up, and avoid the bonk.

When we start talking about energy replacement, we need to talk a bit about gastric emptying. Thatís how fast your stomach/intestines dump their contents into your bloodstream. Too high a concentration of carbs, which can be fructose, sucrose, and maltodextrin, in your drink means your body will actually pull water from your bloodstream to aid in digestion (resulting in dehydration and the occasional trip to the portapotty). The studies Iíve checked out all seem to agree on the optimal level of carb solution being in the 6-8% range, though some people can deal with more. We can all deal with less - water is 0%. Gatorade is 6%, and coke is 10%.

Thereís been a surge in protein consumption and carbohydrate/protein sports drinks lately. The jury is out on the effectiveness of carb/protein fueling during endurance exercise. Protein has 4 calories per gram, and the amino acids contained within (along) may aid in limiting muscle breakdown during exercise. Perhaps more importantly, if you perceive the drink to be more satisfying, and donít experience any gastric distress, a carb/protein drink may work for you. Eating a hunk of meat halfway through the bike will not, unless you plan to ride at 50% of your max for the next hour or two.

Fat. Fat has 9 calories per gram but is tough to convert straight into energy. Some drinks out there do contain small amounts of fat for satisfaction purposes, but the fat you burn during exercise is more likely to come from the stores on your hips, stomach, and butt (or in your head).

Caffeine. Caffeine has zero calories but has been proven several times over to aid in metabolic rate and increase the amount of fat you can burn during exercise (which equals more energy). 1-2 cups of joe pre-race and 50-100mg somewhere along the race course is probably going to help you and probably wonít have too much of a diuretic effect (bathroom). Again, this is very individual.

So, is this too much information, or not enough? In summary, here are the basics of the basics:

  • Drink somewhere between 30-80 ounces of fluid per hour of exercise (more in heat, less in cool)
  • Ingest between 200-1000mg of sodium per hour of exercise (very individualistic)
  • Consume between 150-500 calories per hour of exercise (30-125 grams of carbs and/or protein)
  • You can take in all your calories, water, and electrolytes in liquid form (but donít have to)
  • Practice your nutrition strategy in training
  • Donít worry about any of this for workouts and races lasting less than 1hr; water and a pre-race/post-race meal is just fine
  • A serving or two of caffeine will probably aid your athletic performance

You also need to note that itís unlikely you can replace 100% of what you sweat out and burn off during exercise because of the challenges associated with exercising at intensity. What you need to do is take in enough to keep you operating as close to peak efficiency as is possible under the conditions until the finish Ė where you can pig out on salty pizza and your favorite sports drink. Or beer. Which does have carbs in it!

Some Sports Drinks and their Make-up


Drink Name

Sodium/Serving (8oz)

Carb/Serving (8oz)

Protein/Serving (8oz)











High fructose corn syrup, maltodextrin

Carbo Pro




Glucose polymer







Glucose, fructose, whey protein






Sucrose, whey protein concentrate, maltodextrin





High fructose corn syrup

Beer (light)




Sucrose, alcohol (7cal/gram)

Marty Gaal - One Step Beyond