Is ‘Zone 2’ the Magic Effort Level For Exercise? We Take A Close Look.

Last week's New York Times article Is ‘Zone 2’ the Magic Effort Level for Exercise? is a lovely and simplified presentation of recent research and popular claims. Alex Hutchinson, as he always does, helps us understand the scientific mumbo jumbo by re-framing it into easy to a relatable, understandable way.

Here's a summary of the article:

Zone 2 training, popularized by Dr. Peter Attia and based on the research of Dr. Iñigo San Millan, emphasizes long, steady-state exercise at a specific intensity that maximizes fat-burning while improving mitochondrial efficiency. Advocates claim that spending a few hours per week in this zone can enhance metabolic health, helping to prevent chronic diseases like type 2 diabetes and heart disease. While elite endurance athletes have long incorporated this type of training, the recent surge in interest, fueled by biohacking culture, has led to debates over whether Zone 2 is uniquely beneficial or just one piece of an effective workout strategy.

Scientific research on Zone 2 remains inconclusive. While observational data suggest it improves endurance and metabolic function, studies using muscle biopsies indicate that higher-intensity exercise may be more effective for boosting mitochondrial health. Experts suggest that rather than focusing exclusively on Zone 2, a balanced approach—combining easy, moderate, and intense workouts—yields the best results for both performance and longevity. Ultimately, the most effective exercise routine is one that is both sustainable and enjoyable, ensuring consistency over time.

Here's my take on zone 2 training and the claims made around it's effectiveness...

The excitement around Zone 2 training seems to stem largely from non-athletes who experience significant fitness improvements when they start exercising, even at mild intensities. This is an important distinction because, for seasoned athletes, the marginal benefits of emphasizing Zone 2 are likely much smaller. Peter Attia’s suggestion to begin with two 30-minute sessions per week illustrates this well—such a volume would represent a drastic reduction in training load for most dedicated runners. If Zone 2 training is being promoted as a magic bullet, it’s crucial to acknowledge that its greatest impact will be on those starting from a lower fitness baseline rather than those already training extensively.

The growing popularity of Zone 2 training also reflects a broader trend: the search for an easy shortcut to athletic excellence. It’s no surprise that a method requiring low-intensity effort has gained traction—people are naturally drawn to the idea that they can achieve great results with minimal strain. However, as with any training philosophy that promises outsized benefits with relatively little sacrifice, it’s important to remain critical. Training adaptations occur through strategic and sometimes uncomfortable stimuli, and while Zone 2 has its place, relying on it too heavily as a performance-enhancer is likely misguided.

Furthermore, the research supporting Zone 2’s impact on mitochondrial function must be viewed through the lens of sport specificity. If an athlete spends a substantial amount of time training in Zone 2, their body will naturally become more efficient at that intensity. But the same principle applies to any training zone—consistent exposure to Zones 3, 4, 5, or 6 will lead to adaptations suited to those efforts. The takeaway here is not that Zone 2 is uniquely beneficial but that a well-rounded training plan, incorporating a variety of intensities, is essential for overall development.

That said, I do see value in the argument that Zone 2 training is easier to recover from. For athletes balancing work, family, and other responsibilities, recovery is often the limiting factor rather than the training itself. If a runner struggles with fatigue and burnout due to insufficient recovery time, incorporating more Zone 2 training might be a practical way to maintain consistency without overloading the body. While elite athletes may require a higher percentage of high-intensity work to maximize performance, recreational runners who have limited time and energy could benefit from the sustainable nature of Zone 2.

Ultimately, Zone 2 is not a revolutionary training hack but simply one tool among many. For new exercisers, it provides a structured and accessible way to build aerobic fitness. For experienced runners, its greatest value may lie in its ability to facilitate recovery and overall training balance. However, as with any training methodology, it should be incorporated strategically rather than blindly embraced as the key to peak performance.

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