Improving Glycogen Efficiency

Will reducing your carb intake during training translate to a faster marathon?

In recent years there have been many different training methods that coaches and runners have been experimenting with. One of them being a decrease in carbohydrates during training in order to improve glycogen efficiency. The theory is that when we train with low carb availability our bodies respond by being more efficient with what’s left. The body adapts. The purpose being that when our glycogen stores are at full capacity, and our glycogen efficiency is at its best, that it will allow for a faster marathon performance.

Now let’s dig deeper into this. In a way, training with less carbs can be counterproductive since it is known that the availability of carbs when running is a big factor in how we perform. However, if we can occasionally train with low glycogen stores it can allow us to optimize our utilization of fat as fuel and better preserve our glycogen stores for later in a marathon. But does this method actually work? Let’s break it all down.

To get started how can we achieve low carb availability? There are actually a number of ways to reduce the availability of carbs during training but the main method is through changes to our diet. Examples: consuming a diet low in carbs, withholding carb intake during longer training sessions, or delaying carb intake for the first few hours after a hard workout.

But what does the research have to say about this method? It has been proven that adaptions to training are enhanced when running with low glycogen stores. It has been shown that training in a fasted state promotes different training adaptions compared to runners who consume carbs before or during training. However, it’s still unknown whether or not the adaptions translate into an increased performance on race day. The main issue with this approach is although training with low glycogen during a hard workout results in enhanced muscle adaptations, these runners had a lower power output during that workout compared to runners with high carbohydrate availability. Meaning they weren’t able to run as fast. So do the enhanced training adaptations make up for a decrease in training performance.

Most research says that the availability of carbs during intense exercise is a key determinant of success. There is no clear evidence from the studies to support a performance advantage from the train low strategy. But, there is a different approach that could help runners improve on race day. We know that training overall with less carbs may not increase our performance but using this approach periodically has it’s benefits. So how would this be structured?

There are a couple ways this can be done. First, doing 1-2 easy runs during the week in a fasted state. Meaning only water beforehand. This is where a runner should start if they’re wanting to experiment with low glycogen training. Next, let’s take it to the next level and use this same approach for a long run. You’ll want to reduce carbs the day prior and then only have water prior to the run. Also, no fueling during the run. Just water. Of course you’ll want to have some gels or a sports drink on hand just incase. These runs are done at an easy pace and you should only plan to do 2-3 of these during the training cycle.

In conclusion, if you decide to experiment with this approach, you should include both glycogen depleted and glycogen loaded runs. By doing this you can improve glycogen efficiency while also maintaining consistency in your training.