Glycogen Part 2 – Glycogen Use and Replenishment Video.

Glycogen Part 2 – Glycogen Use and Replenishment Video.

In today’s master Class we look at some of the many misunderstandings around Glycogen in our tribe, and specifically around its replenishment following a High-Intensity Training Event – eg Weight Lifting or HIIT Cardio.

We answer a few questions like

Does Intra Workout Carbohydrate Nutrition make sense for our Tribe?

What sources of Carbohydrates work best for Glycogen Replenishment?

What about Carbohydrate Intake Timing , does it matter ?

As always if you have any questions feel free to ask

If you want to find out more watch these Master Class Videos

Video – Linear VS Non Linear Caloric Intake – More Carbs on Training Days

Video – Pre, Intra and Post Workout Nutrition

What is Glycogen?

What is Glycogen ?

Muscle cells need a source of energy in order to sustain the contraction of skeletal muscles during intermittent and continuous exercise.

That source of energy is ATP or Adenosine triphosphate

ATP is produced in one of two ways

1, from the oxidation of fatty acids from the bloodstream and from intramuscular triglyceride stores

2 with glucose supplied by the bloodstream and intramuscular glycogen stores.

During exercise at intensities greater than approximately 60 {4810c8228756a9189e64fcffe2b64504834fd1a9aa1761a0e9a85eac56097be8} maximal oxygen consumption (VO2max), blood glucose and muscle glycogen are the primary fuels oxidized to produce the ATP required to sustain exercise.

This is in large part because more fast-twitch motor units are recruited as exercise intensity increases, increasing the reliance on carbohydrate as the predominant fuel source in Weight Lifting.

Glycogen is a Particle not a Molecule

Because glycogen is comprised of individual glucose molecules, there is no such thing as a glycogen molecule; it is more accurate to refer to a glycogen particle or even nodule

Glycogen Particles can vary widely in size due to differences in the total number of glucose molecules within each particle.

Glycogen Distribution with the Muscle Cell

Glycogen particles are distributed at different locations within the muscle cell to support the local energy needs of the cell during exercise.

Intermyofibrillar glycogen particles constitute roughly 75 {4810c8228756a9189e64fcffe2b64504834fd1a9aa1761a0e9a85eac56097be8} of total muscle glycogen and are conveniently located adjacent to the sarcoplasmic reticulum and mitochondria.

Intramyofibrillar glycogen particles are dispersed among the contractile filaments and represent 5 –15 {4810c8228756a9189e64fcffe2b64504834fd1a9aa1761a0e9a85eac56097be8} of total glycogen

Subsarcolemmal glycogen particles—another 5–15{4810c8228756a9189e64fcffe2b64504834fd1a9aa1761a0e9a85eac56097be8} of total glycogen—are found between the sarcolemma and the contractile filaments.

How are Glycogen Particles formed?

All glycogen particles are initiated by glycogenin, an enzyme that forms a complex with glycogen synthase to link uridine diphosphate–glucose molecules to create the beginnings of a glycogen particle. Glycogen synthase and branching enzyme then work in concert to enlarge the glycogen particle.

The regulation of glycogenin formation is not well understood, but the cellular content of glycogenin influences the rate and extent of glycogen storage.

As mentioned above Glycogen particles can be categorized into 2 forms based upon their size:

1) proglycogen


2) macroglycogen.

Proglycogen particles comprise roughly 15 {4810c8228756a9189e64fcffe2b64504834fd1a9aa1761a0e9a85eac56097be8} of total glycogen content, are very sensitive to dietary carbohydrates, and are first to add glucose units after glycogen depletion – however the important takeaway here.. they are only 15 {4810c8228756a9189e64fcffe2b64504834fd1a9aa1761a0e9a85eac56097be8} of the total glycogen content.

Additional glucose units are then more slowly added to create the larger macroglycogen particles.

Restoration of Glycogen following Exercise ( not supercompensation we will address that in Part 2 )

After exercise, the restoration of muscle glycogen occurs in a biphasic manner.

During the first phase, glycogen synthesis is rapid (12–30 mmol/g wet weight/h), does not require insulin, I will say that again does not require insulin and lasts 30–60 minutes if glycogendepletion is substantial.

The second phase depends on insulin and occurs at a slower rate with euglycemia (2–3 mmol/g wet weight/h), a rate that can be increased to 8–12 mmol/g wet weight/hour with additional carbohydrate intake.

Periodic carbohydrate supplementation can result in supercompensation of glycogen stores, an advantage after tasks requiring hours of sustained physical effort. In fact, the secondphase effect can be sustained for several days when carbohydrate intake is maintained

So a couple of takeaways here

1, If you are on a Low Carb Diet you are still depleting and restoring Gylcogen when you undertake High-Intensity Activity.

Where does that Glycogen come from?

If you don’t eat enough Carbohyrdates to need, then its coming out of your Protein Intake, consider that carefully. This is why they say Carbs are Protein sparring.

2, Replenishment is bi-phasic ie it happens in two stages

The first is the rapid burst in the 30 – 60 mins following training and does NOT require Insulin and represents about 15{4810c8228756a9189e64fcffe2b64504834fd1a9aa1761a0e9a85eac56097be8} of total ” capacity”

The second is much slower and happens over the 24 hours + period following training

Part II tomorrow

Victor Black