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High Intensity Fuel Shifting

Meaning

High intensity fuel shifting is the acute physiological ability to rapidly transition between different primary energy substrates—specifically from fat oxidation to carbohydrate (glycolytic) metabolism—in response to sudden, high-demand physical or cognitive stress. This represents an advanced level of metabolic flexibility, which is crucial for supporting peak physical performance and rapid cognitive mobilization under pressure. The efficiency of this transition dictates both the performance ceiling and the subsequent recovery time.