Fuel for Thought

Weekly Column By Barb Bryan, BSc(Pharmacy), BSc(Nutrition) APA PRESCRIBING RIGHTS

Macronutrients – Part 3 in a 6-part series.

Carbohydrate nutrition before, during, and after exercise.

Last week we dove into the science side of how we nutritionally define three basic types of carbohydrates found in food. This week we will cover carbs as nutrition before, during, and after exercise.

Whether you are a weekend warrior or a professional athlete, carbohydrates rightfully receive a great deal of attention in sports. We need carbohydrates because:

  • They are the building blocks for our body’s glycogen (the main fuel your muscles and liver will store and use during training and racing). It’s also the main fuel for the brain and central nervous system for enhanced mental focus.
  • They are an easy fuel option chosen directly before and during exercise. When compared to fat and protein they are easier to digest and generally well tolerated and preferred by most athletes.
  • They are the only energy source that can be used right across the heart rate zones. Your body uses 2 types of metabolism during exercise to provide the fuel needed for your muscles. We define them as aerobic, (easy, sustainable) and anaerobic, (red zone, pushing hard). Anaerobic metabolism can only use glucose, while aerobic metabolism can easily use glucose but can also break down fats and protein. Your body will naturally switch between aerobic and anaerobic metabolism during your workouts to get the job done.

There is also strong evidence to support the fact that carbohydrate availability improves performance. Whereas, depletion of our stores without strategies to maintain them is associated with fatigue, reduced work rates, impaired mental focus and increased perception of effort. Directly after prolonged or intense workout sessions, specifically within the first 30-90 minutes, it is vital that you replace that muscle glycogen permitting you to come back ready for your next workout.

Figuring out what works best for each individual takes trial and error. We are all different and these differences, as mentioned in part 1, determine our athletic nutrition plan. While it is recommended that athletes work with a nutrition expert to fine tune what is best for their sport and unique body, there are some fundamental guidelines below that everyone can follow.

Carbohydrates Before Exercise – “Pre-Fueling”

Sessions and Events > 60 mins and those sessions with significant amounts of intensity

In an ideal world, for intense training or workouts lasting longer than 60-90 minutes, we would wake up at 5 am and eat 1-4 grams of carbs / 1kg body weight about 1-4 hours before our morning training session or race. You want this to be some easily digestible complex carbohydrate to top off your liver glycogen, which your body has utilized during your fasted sleep to maintain proper blood glucose levels. You especially want to do this if you have a long training session or race lasting more than 90 mins. Muscle glycogen, however, is left intact while you sleep. So, if you properly recovered nutritionally from the day before, your muscle glycogen will be topped up and ready to go – we will discuss this in detail in a later article.  If you haven’t properly refueled the tank from the previous session, however, it will be somewhat empty and there is not much you can do about it at this point. As a result, your workout or race may be a “sufferfest” with decreased performance.

In general, studies have shown, foods with low fat, low fiber, low spice and low-moderate protein content are preferred for a pre-exercise meal since these are less likely to cause GI issues. For athletes with pre-event nerves and uncertainty about the start times of their sessions or events, a quickly digestible option may be best, such as a smoothie. However, practice makes perfect and this pre-fuelling strategy should be exercised consistently during training to find out what works for you.

Some Examples of > 60 mins Pre-Workout Meals

  • A cup of oatmeal topped with banana
  • English Muffin and egg
  • Tart Cherry Juice and egg whites
  • Sweet Potato with and egg baked in the middle

Sessions and Events < 60 mins and lighter in nature

For a low intensity workout less than 60 minutes you can eat what you’d eat on a normal rest day. Again, if you properly recovered nutritionally from the day before your muscle glycogen will be topped up and you are ready to go for this session without much pre-fuel, if any. Our muscles hold about 1200 – 2000 calories as glycogen so this would get us through a low-intensity short session. However, studies have consistently shown that small amounts of simple carbs right before a short session or race can increase glycogen utilization while boosting carb burning during exercise thus potentially improving performance.

Some Examples of <60 mins Pre-Workout Meals

  • Banana
  • Diluted tart cherry juice
  • 1/2 English muffin with homemade blueberry jam


Carbohydrates During Exercise – Performance

Sessions and Events < 60 mins and lighter in nature

During shorter periods of low-intensity exercise, carbohydrate intake may not be considered necessary.

Sessions and Events > 60 mins and those sessions with significant amounts of intensity

During exercise lasting > 60 minutes or sessions that are shorter in duration but higher intensity, an intake of simple disaccharide carbohydrates during the activity will improve your performance.

There are also some interesting studies that show mouth rinsing and spitting with a simple carbohydrate solution during these workouts can reduce the perception of effort through the activation of the reward centers in the brain. Obviously, we must ingest some carbs to replace our lost glycogen in an endurance event, but this may be a useful technique for those of us who have a very sensitive stomach. We also must remember a substantial body of evidence suggests that the GI system is highly adaptable. Gastric emptying, as well as stomach comfort, can be “trained”.  So, practicing fuelling during training for an endurance event is vital.

Current recommendations to top up blood glucose levels and delay fatigue:

  • 45-75-minute workout, high intensity – 30 grams of carb/hr is enough (e.g. a gel has about 22-30g)
  • 1-3-hour workout – 30-60 grams of carb/hour (e.g. 1-2 gels per hour)
  • 3+ hours – 90 grams of carb/hr (e.g. 2-3 gels per hour)

Exceeding these recommendations won’t help since the GI tract can’t absorb any more than that per hour.

There are more and more studies showing now that disaccharide gels containing glucose and fructose may lead to direct performance improvements, better GI tolerance and faster absorption than using a monosaccharide gel. The science is still developing but it may be due to glucose and fructose having non-competitive transporters across the intestinal wall.  (e.g. Gels such as Honey Stinger and Endurance Tap Maple Syrup)

There’s no one “best” option for what to eat during exercise and it will depend on what your individual preferences and requirements are. The more you familiarize and practice race nutrition, the more efficient your body will become at processing carbs on race day. Yes, this will require some time, but, we have time right now since we are in the base training block.

Carbohydrates After Exercise – Recovery

Carbohydrates are the most important part of post-exercise nutrition because they enable glycogen store restoration. Restoring glycogen ensures we are ready for our next training session or race. Protein is the other important macronutrient for recovery that we will talk about next week in Part 4.

Sessions and Events < 60 mins and lighter in nature

If your workout was short and or not intense, you may not need a post-workout snack. An easy spin on the bike for 30 mins in Zone 1 may not require a snack after. However, because this is when nutrients are least likely to be stored as fat you might want to have a snack now rather than 1-2 hours later.

Sessions and Events > 60 mins and those sessions with significant amounts of intensity

Rapid replacement of glycogen is important following long or intense exercise. Carbohydrate foods and/or fluids should be consumed directly after exercise, particularly within the first hour.

  • 1 – 1.2 grams of carbs/kg body weight per hour during the first 4 hours after long intense exercise maximizes recovery of glycogen stores. Possibly half of these carbs should be ingested within that hour window and the rest spaced throughout the remaining 3+ hours.

Example – 50kg woman @ 1 gram of carb/kg

=200 carbs over 4 hours with about 50% of those consumed in the first hour. You may want to have a prepared smoothie containing 100g of carbs ready

E.g. 1 banana, 1 cup of each (blueberries & raspberries) and 1.5 cups of chocolate almond milk and protein

In Summary: This week we talked about carbohydrates and how before and during a workout, our goal is to increase the delivery of glucose to our working muscles to maintain glucose levels and postpone fatigue. After we are done training the focus shifts to replenishing glycogen stores and initiating tissue repair and growth. This will ensure you are ready for the next workout.