A client of mine recently asked me “why is it that I need to fuel my morning training” and instead of giving her a generic “you need fuel to train” type response, I broke down the science on WHY she needs to fuel and I bet it will help you as well.
First and foremost, she needed to understand basic exercise metabolism, that is how our body uses fuel when we exercise. Our body predominantly uses fats at lower intensities, and as the intensity of activity increases, we use more carbohydrates for fuel. The point at which we use predominantly carbs over fats is 60% of our maximum intensity.
Now this is an important point that many brush over, which is much lower than what you would expect. Let me explain. This client is 35 years old, her max heart rate (220-35) is 185bpm (beats per minute) and her resting heart rate is 60bpm. Now that means there are 125bpm between her resting and her max heart rate. If we work out 60% of that (125 x 0.60%) we get 75 and if we add that to her resting (60bpm + 75bpm) we get 135bpm.
This is the heart rate which corresponds to 60% intensity ie when her body is predominantly fuelling with carbohydrates.
Now think about this. What activities do you do where your heart rate is 135bpm or above? Most, if not all of your workouts. That means that the majority of your workouts are fuelled predominantly by carbohydrates. The next question to address is how much do you need?
To answer this you need to know that you store carbs in your body in the form of glycogen and you can store that both in your liver and your muscles. The more muscle mass you have the more glycogen you can store.
The average person stores 120g of glycogen in their liver and 400g of glycogen in their muscles. Now consider that to keep your blood sugar levels balanced your body will use 120g of of carbs, you are left with 400g. How much do we burn during exercise?
Well, it depends on many factors, but on average you can expect to burn 2 grams per minute during exercise and 4 grams per minute during really intense exercise. So, let’s be conservative and say 2 grams per minute that is 120 grams per hour. So, if you are fully glycogen loaded you have enough fuel to do two hours of moderate-intensity exercise and one hour high intensity exercise.
The last piece of this puzzle is to understand that glycogen resynthesis or replacement, takes up to 24 hours. This means if you deplete your glycogen, it will take an entire day to fully replace it.
So let’s answer my clients question; yes, you do need to fuel your morning training. Overnight, your body burns through your stored liver glycogen. If you ate a good high carb diet the day before, you have access to 400g of muscle glycogen. Your body will need a further 120g of that to just get through the day. You are left with 280g and that is only 2 hours until you are completely empty.
Now your body will never let you get empty of glycogen. If you even approach 20% empty you will experience extreme physical and mental fatigue. Therefore, if you want to get the most out of your training, follow these steps; eat well the day before (meaning eat well each day if you train everyday), eat a small amount of carbs right before your workout (aim for 30-60 grams), and immediately after your workout start the resynthesis by having a healthy high carb meal.
If you do this everyday then you can be rest assured that you can; consistently train while managing fatigue, recover properly, train at the desired intensity for the duration of training, adapt as best as possible to your training.
Now go and eat some carbs!