The protocol consists of two workouts in one day, the first is a high intensity interval session, followed by a low intensity aerobic session within a 4 hour window. Both workouts are done in a fasted state.
The intended benefit is to increase mitochondrial density in the muscle fibres and to improve fat burning for fuel.
The first session should be done fasted, usually first thing in the morning. A typical workout would be a Tabatha Session of 4 x 40 secs hard, 20 secs recovery with 1 minute between sets.
The second session is an easy aerobic session of an hour long. What the athlete will typically observe is that even small increases in effort push the heart rate abnormally high as the body attempts to find fuel somewhere in the system.
There must be no fuel of any kind taken in between the two sessions. The athlete can drink water with electrolytes but that’s all.