It means that the majority of your energy is being provided by the aerobic metabolic pathway. Raising your heart rate doesn't mean it's aerobic. There will alwa

It means that the majority of your energy is being provided by the aerobic metabolic pathway. Raising your heart rate doesn't mean it's aerobic. There will always be a contribution from the aerobic pathway, but if the instantaneous demands are too high then anaerobic pathways provide most of the power. Intuitively, the pathway that's providing most of the power is the pathway that gets the most training effect.