“Zone two is a metabolic state. It’s not determined by speed. It’s determined by which energy system you’re requiring and what the equilibrium is.” —Peter Attia
“What I have been seeing for 25 years, working with elite athletes, is that [zone 2] is the exercise intensity where I see the biggest improvement in fat burning and the biggest improvement in lactic clearance capacity. Therefore, that means that the mitochondria is where you see the biggest improvement.” —Iñigo San Millán, Ph.D.