Zone 2 Training from Readwise

Here is information about Zone 2 trainign from my Readwise highlights.

Summary

Zone 2 training is moderate-intensity exercise you can maintain while just holding a conversation, recommended for 150-180 minutes a week for most people, and is central to metabolic health, mitochondrial function, and healthy aging. It does not impair muscle or strength gains if kept truly in zone 2, and its regular practice may be a potent tool for longevity and disease prevention.

Key Points

1. What zone 2 training is:
Zone 2 refers to a specific heart rate or effort level during endurance exercise—usually described as a "conversational pace." This is an intensity at which you can just barely still carry on a conversation, but if you push any harder, you would not be able to do so. It is widely recommended for general health, even for people who focus on strength and muscle gains, with strong evidence suggesting it won’t negatively affect hypertrophy if really kept within zone 2 conversational pace recommendations.

2. Zone 2’s Metabolic and Mitochondrial Benefits:
Zone 2 training enhances mitochondrial function and metabolic health. Inigo San Millán and Peter Attia discuss how exercise at this intensity level improves the efficiency of mitochondria, which play a central role in oxidizing fuels and overall cellular longevity. This type of training is thought to be a crucial differentiator between living healthy into old age and having health decline earlier mitochondria and metabolic efficiency and cellular longevity and zone 2.

3. Heart Rate and Duration:
The “zone” is typically set at a heart rate where fat oxidation is high and lactate remains at stable, low levels. At higher intensities (zone 3 and up), you exceed your mitochondria’s capacity to provide energy through fat oxidation and become more glycolytic, meaning the body shifts toward carbohydrate metabolism, and lactate accumulates more quickly zone 2, lactate, and energy systems.

4. Recommended Amount and Frequency:
You’ve noted a general prescription, based on literature, of 150 to 180 minutes per week of zone 2 cardio for health and longevity. This can be divided into 3-4 sessions per week, with each lasting from 45-90 minutes depending on the baseline fitness and health status of the individual how much zone 2 is enough?. Elite athletes might need much more, while those with metabolic conditions (like type 2 diabetes) can see benefits with as little as one hour three times per week.

5. Practical Nuance:

• You can do zone 2 every day if desired, even when focusing on strength or hypertrophy, since properly-performed zone 2 does not meaningfully interfere with muscle-building goals zone 2 does not block strength/hypertrophy.
• Zone 2 is best monitored with heart rate (often 60-70% of max, or vaguely 120-140 bpm for many adults, but personal testing is best) or by ensuring a conversational pace.
• If you push much harder, you may enter zone 3, where benefits become different and you lose the distinct mitochondrial adaptations of zone 2 zone 2 vs. zone 3.

6. Longevity Implications:
Inigo San Millán and Peter Attia both argue that regular zone 2 training is one of the most important things you can do for cellular health and lifespan extension zone 2 and being a healthy 90-year-old.