Every time we head out for a training session, our sole purpose is to improve a specific energy system (i.e. anaerobic, aerobic and their subgroups). The expanding technology base and coaching knowledge helps us pinpoint each system with specific workouts. While both tech and knowledge are expanding, one thing we aren't talking about is how we fuel to support the training of the energy systems.
In order to get the most out of our sessions, our nutrition needs to parallel the training. This means that we consume not only an adequate amount of calories around training, but also the proper macronutrient breakdown. For example, you don't want to go on a low carb or no carb diet and then attempt intervals at threshold intensity. On the flip side, if you consistently consume a lot of sugar before lower intensity workouts, you hamper your body's ability to rely on stored energy.
We have outlined some example on how to plan your fueling for training sessions based on the intensity.
Lower Intensity
This is typically an effort of Zone 1 & 2, less than 70% of your max heart rate (HR) or an RPE of 1 - 4. This effort is usually for recovery up to aerobic threshold and where the majority of ultra endurance racing takes place.
For shorter workouts you can rely on stored energy, but as the length of the workout progresses, you will want to use a balance of macros so you do not overload your system with too much carbohydrate / sugar.
Moderate Intensity
This is typically an effort of Zone 3, 70 - 80% of your max HR or an RPE of 5 - 6. This is where your substrate crossover happens, or the point to where you start to burn more carbs than fat.
Shorter workouts at this intensity can rely on stored energy, but it is important to make sure your body has enough stored glycogen to support the effort. For longer workouts on the lower end of this intensity block, you will want to utilize energy sources that have a balance of macros. As the intensity shifts up, you can shift to easier digestible items that are more carb focused.
High Intensity
This is typically an effort of Zone 4 & 5, 80 - 100% of max HR or an RPE of 7 - 10. This intensity makes it difficult to process large amounts of calories so it is crucial your energy stores are completely full.
Shorter workouts at this intensity can be done without ingested calories, but again, your energy stores must be full. As the length of the effort progresses, simple sugars like dextrose tabs and drinks will be your best bet. Dextrose is absorbed both under the tongue and it passes easily through the gut and into the bloodstream for readily available energy.
Please keep in mind, these are general guidelines. Your specific training load is the greatest determiner of your fueling needs.
