Impey et al. 2018, Fuel for the work required

Impey, Hearris, Hammond, Bartlett, Louis, Close and Morton, “Fuel for the Work Required: A Theoretical Framework for Carbohydrate Periodization and the Glycogen Threshold Hypothesis”, Sports Medicine 48(5):1031–1048, 2018.

A narrative review setting out the “fuel for the work required” paradigm, matching carbohydrate availability to the demands of the upcoming session, and the glycogen threshold hypothesis. It catalogues the train-low methods (twice-per-day, fasted, post-exercise restriction, sleep-low) and reports that training with low glycogen reliably augments cell signalling (73% of 11 studies) and gene expression (75% of 12 studies), but that these adaptations do not consistently translate to performance: 37% of 11 studies showed improvement and 63% showed no change.