The main way to train our system to utilise fat during activity is to move at a steady state. This means our aerobic engine does not venture out of second or third gear. In athletic circles, this is described as “zone 2”, with the heart rate in the aerobic zone.
For a longer session or trail race, fuelling increases in importance. If we go longer and harder, we increase the risk of running out of our premium fuel: carbohydrate (stored as glycogen). Our power output then decreases by 50%. Carbs and fat work