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).
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.
Since high-intensity activity such as weight training can only use carbohydrate as fuel, a SKD will not be able to sustain high-intensity exercise performance. This mandates that carbohydrate be introduced into the SKD without disrupting the effects of ketosis. The two primary ways to introduce carbohydrate to the SKD are the CKD, which allows a period of high carbohydrate consumption lasting from 24-48 hours every week, or the TKD where the dieter consumes carbohydrates around training.
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