Prioritize high-intensity exercise (≥75 min/week) with power training
The standard advice from endurance coaches is that meaningful zone 2 gains require 1–1.5 hours at least four times per week — an impractical volume for most. Stanfield’s rationale is that if you can only exercise a few hours weekly, every minute spent at zone 2 crowds out time that could be spent at higher intensities, which deliver a greater return per minute for mitochondrial function and especially for VO2 max. The better your baseline fitness, the more this holds true because a trained body needs a stronger stimulus to adapt. The protocol therefore recommends meeting the 75-minute vigorous target first, including power training to combine aerobic and neuromuscular benefits, and only layering in zone 2 as a bonus activity.
Intensities above zone 2 place a greater strain on cellular energy systems, triggering stronger signaling cascades for mitochondrial biogenesis and improving the heart–lung oxygen delivery system (VO2 max). The body responds to a sufficiently strong stimulus, whereas zone 2’s low stress produces minimal adaptation without very large volumes.
Stanfield explicitly states this is the advice he gives to his patients: “the advice that I give to my patients is to focus on highintensity exercise done safely.” He contextualizes it with the caveat about building up slowly to prevent injury, reflecting his clinical practice.
So, the advice that I give to my patients is to focus on highintensity exercise done safely. So, if you're starting out, we need to build up slowly, otherwise you're going to risk an injury. And this also includes power training when we're combining higher weights with quick movements. Again, we want to make sure that this is done safely. And the standard recommendation is to aim for at least 75 minutes of vigorous intensity exercise a week.