Some of the most frequent and consistent questions we get at First Endurance have to do with how and what to use for fuel during exercise.  If you have any questions or comments, we’d love to hear from you.  Just comment below and we’ll make sure to get back to you right away.

Rocket Fuel for your Body- Glucose is always circulating in your blood and is the ‘rocket fuel’ for fast paced workouts or races.   In fact, without glucose you are going nowhere fast.   Your body can produce glucose in two different ways.  The first, which also is the most efficient, is by utilizing the glycogen that’s found in your muscles and liver.   This is a fairly fast and efficient method that can deliver a quick supply of glucose to fuel your workout.  The downside is that we only have a couple hours worth of this stored glycogen at best.
The alternative option is for your body to convert non-carbohydrate sources like protein and fat into energy.  Even though we have days and days of fuel stored as protein and fat in our body, this option can be quite inefficient.   The pace at which you are exercising will determine what fuel your body uses.  To a lesser degree your body’s own efficiency also determines what fuel is used. 

Avoid ‘hitting the wall’- Your intensity determines whether your body utilizes fat or carbohydrates to fuel your workout.   For an all-out sprint, your body will use glucose- the most efficient fuel to drive the working muscles.    At a slower pace, or in a situation where you have burned your glycogen, your body will breakdown stored fat for fuel.  Remember: your body has to convert fat to usable energy in order to fuel the workout.    It’s this inefficiency or slow rate at which your body converts the fuel source that causes you, or forces you, to only use this fuel during slow paced workouts.     The dreaded ‘bonk’ is one of those times where you have run out of stored glycogen and you get the sensation of having no energy and being in an extreme state of exhaustion.

Tip: Consuming fast absorbing carbohydrates spares glycogen because these carbohydrates get used instead of your stored glycogen.  In this manner performance remains high whether you are sprinting or going very, very long. 

Teach Your Body a New Trick- The good news is you can condition your body to convert fat to glucose more efficiently.  Not only will this increase your ability to go longer, it will reduce your need to take on additional calories during training and racing. This process uses a systemic method of training long distances on very little carbohydrates in order to train your body to burn fat more efficiently.  This is the premise behind what is called ‘substrate utilization’ or ‘substrate training’ for long distance athletes. This is a significant benefit on race day because you’ll be more efficient at burning fat and sparing glycogen.  This type of conditioning also allows you to consume fewer calories per hour, which often results in a decreased risk of gastric distress.

Tip:  It takes many months to adapt to lower carbohydrate training and racing.  Use a well designed plan that uses lower carbohydrates instead of training with water only.   For fast paced workouts fuel fully. This assures you get great recovery AND substrate training. 

Fueling in Different Conditions:  We’re talking primarily about temperature when we discuss fueling practices in different conditions.   When it’s hot, your body expends a large amount of energy trying to cool itself by dissipating heat.  It does this by circulating more blood to the skin surface so you sweat more.  This leaves less blood to aid digestion AND you require more fluids to keep you sweating at a high rate.

This high sweat rate is a sign of efficient cooling but does require fluids and electrolytes in order to sustain workouts over many hours.

In cooler and even cold conditions where your body does not sweat, you do not need to consume high rates of fluids, but you still need the calories.   Adjust your fluids and electrolytes to match the ambient temperature.

Tip:  If its hot and you will sweat make sure the concentration of your calories is no more than 100 calories to 12oz fluid.   In cold conditions you can double this concentration to 200 calories to 12oz fluid.

Be careful what you eat:  Ingesting slow absorbing fuels like proteins, nuts, fats, foods with fiber and other solid foods during workouts can cause gastric distress as well a premature “bonk.”   Slow absorbing fuels get stuck in the gut, which means your body can’t readily utilize them.   If your body is burning stored glycogen as it waits for those slow nutrients to get absorbed, you’re reducing your 2 hour fuel tank and increasing your chances of ‘bonking.’  To reduce the chances of ‘bonking’ or gastric distress eliminate all slow absorbing nutrients from your fuel plan.

Tip:  An empty stomach can absorb your drink fast and fully.  Keep your stomach empty by only consuming fast absorbing drinks instead of slow solid foods.  In long distance racing, hunger is a sign of an empty stomach its NOT a sign that you are bonking.  Stay hungry my friends. 



How to Use EFS, EFS Liquid Shot and EFSPro for Any Distance:

Whether you are out for an intense high paced 45-minute workout, or about to embark on your 100-mile ultra distance run, EFS products are designed to fuel your workout at any distance.  The below recommendations are loosely based on a 150lb athlete.   In order to properly manage your nutrition its important to first ask these questions.

1) How much will I sweat?  IE: How hot will it be?

2) How long will I go?

3) How fast do I plan to train/race?


New EFS Drink FamilyEFS drink: Designed to be used at an 8% solution (100 calories per 12oz).  Delivers high levels of 5 electrolytes.


efs-ls-ssEFS Liquid Shot:  Designed to be used for cold weather training and racing or as supplemental fuel.  Delivers high calories and low electrolytes.


pro-familyEFSPro drink:  Designed to be used at varying concentrations (80/100/120 calories per 12oz).  Additional nutrient technology helps shuttle electrolytes into working muscles and increases absorption rates in the most extreme conditions.


< 2 hours COOL/COLD conditions:  Because high levels of electrolytes are not critical EFS liquid shot works well in this situation.  Consume 100 calories EFS per hour at a solution between 10%-16%.     This means 100 calories for every 6-10 ounces fluid.    One ounce of EFS LS is 100 calories.  Pour up to 4 ounces in a water bottle and top off with water.

< 2 hours HOT conditions:  Change to an 8% maximum solution.  This means 100 calories to 12 ounces.  For most EFS drink will work great.   If you are prone to cramping or have difficulty absorbing drinks when the pace is high consider EFSPro.

2-5 hours cool/cold conditions:  Consume 200 calories EFS per hour at a solution between 10% and 16%.   This means 100 calories for every 6-10 ounces fluid.  Electrolytes are still not critical, however due to the longer workout a mix of EFS drink and EFS liquid shot works great in this situation.

2-5 hours HOT conditions:  Change to a 8% maximum solution.  This means 100 calories to 12 ounces.  For most EFS drink will work great.   If you are prone to cramping or have difficulty absorbing drinks when the pace is high consider EFSPro.  You can supplement 50% or less of your calories from EFS LS.

5+ hours COOL/COLD conditions:  Consume 250-300 calories EFS per hour at a solution between 10% and 16%.  This means 100 calories for every 6-10 ounces fluid.   For very long distances  your body will balance the use of stored fat, stored glycogen and orally administered calories to fuel the workout.   Consuming only fast absorbing fuels assures that you deliver glucose consistently to the blood, which can help spare glycogen so you don’t bonk.  A mix of EFS drink and EFS liquid shot works great in this situation.  Your PACE will determine how many calories you need.  If the pace is slow, less calories are needed.  If the pace is at threshold you will need more calories.

5+ hours HOT conditions:  Change to an 8% maximum solution.  This means 100 calories to 12 ounces.    At subthreshold pace EFS drink will suffice for most individuals.   At a fast threshold pace, where the body needs high electrolytes and sufficient calories consider using EFSPro as your primary calories.    The longer and the hotter the conditions the more athletes should rely on EFSPro as their primary fuel.   EFS LS can be used as supplemental calories, however this should be limited based on distance and pace.

Tip:  In a race where temperatures will vary during the day so should your nutrition.  Plan your nutrition to match the ambient temperature so in cold conditions you have less fluids and electrolytes and in hot conditions you have more fluids and electrolytes.