Everyone from elite coaches to Instagram influencers is suddenly obsessed with Zone 2 training — but the science behind it is more nuanced, and more interesting, than the talking points suggest. This episode breaks down what metabolic zones actually measure, why the research on mitochondrial adaptation looks genuinely compelling in some contexts and wildly overhyped in others, and how to figure out what intensity actually makes sense for your body and your life. No heart rate monitor required to follow along.