Untrained individuals will improve cardiorespiratory fitness with lower-intensity or zone 2 training because it provides a novel training stimulus.

“if you take a group of people who have never trained before kind of unfit people and just give them a lot of lower intensity or you know what people might refer to as zone two training everybody is going to kind of improve because you have it's a new training stimulus you know you've never trained before you add some exercise okay well obviously you're going to get fitter”