Zone 1: Barely above normal. Light and relaxed
Zone 2: Deep steady relaxed breathing. That’s your aerobic, endurance-training zone. It’s an Rate of Perceived Exertion (RPE) of 3 to 4.
Zone 3: Slightly labored. This is a steady “tempo” pace, where you’re working just a hair above your endurance comfort zone. It’s where you’d be if you were riding with someone just slightly faster than you. RPE 5 to 6
Zone 4: Short, quick rhythmic breathing. This is your lactate threshold zone. Right where you’re hitting your sustainable upper limits. Also known as race pace It’s an RPE of 6 to 8
Zone 5: Hard, gasping-for-breath breathing. This is your VO2 max training zone, which is a fancy way of saying, the top of your limits, as hard as you can go. It’s an RPE of 9 to 10.