The renowned Australian researcher Louise Burke conducted a review that analysed the different nutritional strategies that have been studied in order to maximise glycogen synthesis (See Figure 2).² Until a few years ago, “re-synthesis” glycogen protocols were based on the so-called “window of opportunity” or “metabolic window”, which supported that glycogen synthesis was greater if carbohydrate intake occurred in the later hours (especially the two hours after) following an exercise session than if it occurred later in the day..³ This “metabolic window” could occur because, following an intense training session in which glycogen levels are depleted, a number of mechanisms (including increased insulin sensitivity and cell membrane permeability to glucose, as well as stimulation of the enzyme glycogen synthase) would be activated to promote glycogen re-synthesis.⁴  Therefore, based on these physiological responses, it has been proposed that if there is little time between an intense training session and the next session or competition (e.g. when doing two training sessions on the same day or when competing several times in one day), it is recommended to ingest carbohydrates as soon as possible.

Also based on the activation of mechanisms that favour glycogen re-synthesis after glycogen depletion, it has been traditionally supported that, in order to reach competition with glycogen stores as full as possible, it would be advisable to deplete them a few days before the competition (either following low-carbohydrate diets [<2 g/kg] or by very intense training) and then carry out a “loading” or “super-compensation” phase of carbohydrates (approximately 8-12 g/kg per day) during the two or three days prior to the competition.⁵ However, it is important to note that this strategy can be risky as it can lead to fatigue as a result of training or low carbohydrate availability. In addition, it has subsequently been observed that similar glycogen super-compensation can occur without the need to deplete glycogen in the days prior to competition – thus avoiding the risk of fatigue – by simply increasing carbohydrate intake in the days prior to competition (Sherman et al. 1981). In fact, one study found that glycogen stores can be optimally replenished in as little as one day by ingesting a high amount of carbohydrate (10 g/kg) and reducing the level of physical activity (e.g. by training very lightly or resting the day before the competition).⁶