“Current Evidence Does NOT Support Zone 2 Training”
Brad Stanfield
Aug 21, 2025
Mindsip insights from this episode:
Increase duration of Zone 2 training to stimulate mitochondrial development
For most people, Zone 2 training provides minimal stress to cellular energy systems and may not be enough to stimulate mitochondrial development unless done for very long durations.
Reevaluate Zone 2 training for mitochondrial and fatty acid capacity
A new analysis concludes that current evidence does not support Zone 2 training as the optimal intensity for improving mitochondrial or fatty acid oxidative capacity.
Prioritize 75 minutes of vigorous exercise before Zone 2 training
The recommended protocol is to first complete at least 75 minutes of vigorous-intensity exercise per week before considering adding any Zone 2 training.
Prioritize high-intensity training for maximum health benefits in limited time
If you have limited time, you will get a bigger health payoff from high-intensity training than from spending that time in Zone 2.
Prioritize VO2 max for improved health outcomes
The link between VO2 max and health outcomes like mortality is much stronger than the link with mitochondrial health, and higher intensity exercise is better for improving it.
Question Zone 2 superiority in fatty acid oxidation
It is not clear which exercise intensity is best for improving fatty acid oxidation, but current evidence does not support the claim that Zone 2 is superior.
Increase exercise intensity above Zone 2 to enhance mitochondrial function
Evidence suggests that for non-elite athletes, exercise intensities above Zone 2 are more effective at stimulating mitochondrial changes.
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