40 mmol/kg of glycogen was depleted during the exercise, this small amount would not sustain
exercise performance for long.
However, in a second study, 22 mmol/kg was synthesized after training (9). The major
difference between these studies was that subjects in the second study (9) ate a small
carbohydrate-containing meal the morning of the training session whereas the subjects in the
first (8) did not. The elevation of blood glucose from the pre-workout meal allowed greater
glycogen resynthesis to occur following training in the second study (8,10). This observation is
the basis for the TKD which is discussed in chapter 11.
Summary
In the absence of dietary carbohydrates, the amount of glycogen resynthesis following
weight training is insignificant and will not sustain high intensity performance for very long. This
further stresses the importance of carbohydrate intake for individuals on a ketogenic diet
wishing to perform weight or interval training.
If carbs are taken prior to a workout, there can be a significant amount of glycogen
resynthesis following training depending on the quantity of carbohydrate consumed. This is the
basis of the TKD, discussed in the next chapter.
Section 2: Glycogen depletion during weight training
Having looked at glycogen levels under various conditions, we can now examine the rates of
glycogen depletion during weight training and use those values to make estimations of how much
training can and should be done for both the TKD and CKD.
Very few studies have examined glycogen depletion rates during weight training. One early
study found a very low rate of glycogen depletion of about 2 mmol/kg/set during 20 sets of leg
exercise (11). In contrast, two later studies both found glycogen depletion levels of approximately
7-7.5 mmol/kg/set (8,9). As the difference between these studies cannot be adequately explained,
we will assume a glycogen depletion rate of 7.5 mmol/kg/set.
Examining the data of these two studies further, we can estimate glycogen utilization
relative to how long each set lasts. At 70% of maximum weight, both studies found a glycogen
depletion rate of roughly 1.3 mmol/kg/repetition or 0.35 mmol/kg/second of work performed (8,9).
This makes it possible to estimate the amount of glycogen which is depleted for a set of lasting a
given amount of time (table 2).
Summary
Glycogen levels in muscle vary depending on a number of factors including diet and training
status. While there is a small amount of glycogen resynthesized following exercise even if no
carbohydrates are consumed, the amount is insignificant and will not be able to sustain exercise
performance for more than a few workouts.