Cardio should include 150 minutes of zone 2 exercise per week, characterized by the ability to maintain a normal conversation.

“Zone 2 cardio is the kind of cardiovascular exercise in which you're pushing yourself to move such that you're breathing faster than normal, your heart is beating faster than normal, however, you are still able to sustain a conversation. But if you were to push yourself any harder, that is move faster or go up a steeper incline at the same rate you happen to be at any one moment, you would lose that ability to speak, you wouldn't be able to complete sentences, you would be out of breath or you'd have to pause mid-sentence.”