Optimising your glucose levels looks different in training than in recovery.

In this article, we'll discuss:

  • What is your Glucose Recovery Zone?
  • What are some potential downsides of spiking above my GRZ?
  • What are some potential downsides of dipping below my GRZ?

Glucose: it’s everywhere and ever useful. We know that all human cells can use glucose for energy, and glucose is always present in the blood. In healthy individuals, glucose levels are regulated by insulin and glucagon; insulin triggers glucose absorption, bringing your glucose down, and glucagon triggers glucose release, bringing your levels up.

What is a Glucose Recovery Zone?

Your Glucose Recovery Zone (GRZ) represents the glucose levels you should maintain outside of training. By default, it is set to 70-140 mg/dL, but you can constrict or expand it based on your typical glucose regulation or desired adaptations.

What are some potential downsides of spiking above my GRZ?

A key component to glucose management is insulin management. When your blood glucose spikes above 140, your body is exposed to peak rates of insulin secretion. This may cause metabolic perturbations or disturbances linked to inflammation and hormonal imbalances. You can learn more about your body's response to different glucose zones here.

Over time, over-exposure to insulin can also make your body enter a state in which it prefers to store glucose as fat rather than readily utilise it. Reducing inflammation and managing hormone levels is key to recovery, so it’s important to minimise steep glucose spikes.

What are some potential downsides of dipping below my GRZ?

On the flip side, it’s important to keep your glucose levels above 70 to help promote recovery. Muscle and skeletal glycogen replenishment are imperative when recovering from high-intensity training sessions. Dropping below 70 may reduce your available glucose to the point that replenishment, and therefore recovery, is impeded.

What do we mean by all of that? Basically, managing glucose levels within this range when you are not actively training* may help to minimise inflammatory responses while supporting glycogen replenishment — preparing you for a more stable energy provision to support fuelling needs and maximise training adaptations.

*Note: during training, your muscles have the ability to uptake glucose without the need for insulin. This means that, in training, you do not get the same hormone responses when your glucose levels are over 140 mg/dL. Consequently, these elevated glucose levels in training do not pose the same negative effects as during recovery. Instead, they can help to enhance performance by increasing glucose supply to the working muscle.

All in all: Don’t sacrifice your performance with insufficient glucose levels during recovery. Be sure to maintain your Glucose Recovery Zone throughout recovery. You work too damn hard in training to let your days off be your downfall.


  1. Frayn K.N., 2013. Metabolic Regulation: A Human Perspective, 3rd Edition, 2013. Wiley.
  2. Wang C., et.al.,  Glucose fluctuations in subjects with normal glucose tolerance, impaired glucose regulation and newly diagnosed type 2 diabetes mellitus. Clinical Endocrinology. 76-6, 2012.
  3. Wasserman D.H., Four Grams of Glucose. Am J Physiol Endocrinol Metab. 296-, 2009.