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Why Glycogen Matters - 3 Things to Remember

Jill here - the 2019 season is slowly closing. I'm willing to bet that for many of you, your mind is already drifting towards open roads and big winter training blocks. It's important to fuel those big blocks correctly to ensure progression and gain. After all, 2020 is not far away!

I often get asked about fueling strategies for big mileage so over the next while I'm going to offer bullet points and tips on a variety of topics. Nothing too onerous, just the run down.

Let's start with glycogen, the storage form of carbohydrate found in muscles and to a lesser extent, liver.

But first, a brief recap.

- your main sources of energy are carbohydrate and fat, either ingested or stored

- carbohydrate that you ingest but cannot use is stored first as gylcogen, then fat

- any fat that the body cannot use is stored as, surprise surprise, fat

- your capacity to store glycogen is limited by the amount of available lean muscle mass

- your capacity to store fat is unlimited

An athlete who eats a lower carbohydrate diet (less than 40-50% of total intake) both on and off the bike, will likely have less glycogen stored verses an athlete who eats a higher carbohydrate diet (above 50%). Bear in mind that glycogen accounts for about 1-2% of the total weight of your muscle mass so small weight fluctuations can occur depending on how much glycogen your body has tucked away.

To put it in real terms you likely have a range of 15-30g of glycogen stored in each kilogram of lean muscle mass - depending on the amount of carb you eat, the amount of training you do and how specific your recovery is. Each gram of glycogen once converted into glucose provides 4 calories.

Estimate how much lean muscle mass you have and do the math.....this is your glycogen store or your most accessible energy reserve.

Regardless of your on-bike fueling strategy, maintaining your glycogen store for a rainy day is smart.

Here are three simple things to remember.

1. You can only access the glycogen in the muscles you're currently using so for cyclists think quads and lower-legs. These muscles account for about 35% of your lean body mass so you likely have less accessible glycogen in reserve than you think. The relatively small amount of glycogen stored in your liver can be used as needed and usually provides an additional 350-500 calories.


2. Glycogen is still important for cyclists who are deliberately restricting carbohydrate to encourage a shift towards using a greater percentage of body fat as energy.

You always need some carbohydrate to fuel the various metabolic pathways that are responsible for breaking down and utilising fat. The question is how much? And under what circumstances does that carb amount vary?

In a situation where you've restricted carbohydrate too much or you've miscalculated your training effort or perhaps you've simply run out of food, your muscles need to be able to source carbohydrate through your glycogen stores so that the metabolic processes necessary to produce energy from fat can continue.

In this situation, which is akin to a fasted ride with glycogen on board, you're still encouraging that shift towards an increased fat utilisation.

You can't do this in a no-carb, no-glycogen environment.

For sure, it's a challenge to balance carbohydrate input with training output at the best of times. This challenge increases significantly the further you go.


3. There are a couple of telltale signs that your glycogen stores are coming to an end - your brain struggles, your ability to generate power declines rapidly, your sweat or breath may start to smell of ammonia. Of note, the smell of ammonia is a sign that the body is resorting to breaking down muscle to amino acids that can be converted into glucose. This is not a place you want to be.

Luckily though once you ingest a carbohydrate source the body is incredibly adept at replenishing glycogen. You've heard me say it before, drinking 8oz of chocolate milk at a carb:protein ration of 2:1 is as good a start at glycogen replenishment as any fancy recovery drink.


On-bike nutrition is a huge topic especially for endurance folks as distance brings numerous challenges and complications with bigger and bigger consequences.

Consider glycogen your back-up while you figure it all out. It's a limited back-up so make sure you replenish it post training and take care of it. You just never know which cold or wet winter day you'll need it to get you home.


If you're interested in learning more about how to make nutrition work for you drop me a line at or check out our performance coaching section. Both Joe and I are available for one-on-one coaching.

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