A 2025 narrative review in Sports Medicine challenged the broad claim that Zone 2 is the optimal intensity for improving mitochondrial capacity and fat oxidation in the general population (Storoschuk et al., 2025- https://link.springer.com/article/10.1007/s40279-025-02261-y). They argue that a big chunk of the Zone 2 hype comes from observing elite endurance athletes… who train huge volumes. For the rest of us, the evidence suggests higher intensities (above Zone 2) may be