The Truth About Zone 2 Cardio, Mitochondrial Health & How REHIT Beats It (In Less Time!) With Ulrich Dempfle

Ben Greenfield

Apr 24, 2025

Episode description

In this episode with repeat guest Ulrich Dempfle (you can check out our first show together here), you’ll get to explore what actually works when it comes to cardio—whether you’re chasing peak performance, fat loss, or just trying to live longer and feel better.

Whether you’re short on time or just want results without the guesswork, this episode is packed with cutting-edge insights to help you train better, live longer, and stay metabolically sharp.

Full show notes: https://bengreenfieldlife.com/zone2myth

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Mindsip insights from this episode:

Utilize heart rate variability to determine lactate threshold

New technology can precisely find your lactate threshold by analyzing the complexity of your heart rate variability using a method called detrended fractal analysis.

#HRV

#lactate

Leverage AI for optimal sprint resistance on Carol Bike

The Carol Bike uses AI to learn from millions of rides to create the optimal resistance for you during a sprint, ensuring you fatigue at the perfect rate for maximum benefit.

#AI

#exercise

Prioritize high-intensity training for women’s fitness

Since women naturally have more slow-twitch fibers and greater mitochondrial density, high-intensity and resistance training should be a higher priority for them than Zone 2 training.

#exercise

#women

Maximize fitness with two 20-second sprints

Two 20-second sprints at maximum intensity can create a robust training stimulus for improving VO2 max and mitochondrial biogenesis in far less time than traditional cardio.

#mitochondria

#VO2-max

Avoid scratched non-stick pans to prevent microplastic release

According to a study in Science of the Total Environment, a single scratch on a non-stick pan can release approximately 9,100 plastic particles.

#environment

#microplastics

Question the validity of 'Zone 2 training' concept

The term 'Zone 2 training' is not a scientifically defined concept and is rarely studied in research labs, leading to inconsistent definitions and recommendations.

#research

#zone-2

Reserve 80/20 training for professional athletes only

The 80/20 training model is not necessarily optimal for the general public, but rather for professional athletes who train 25-35 hours a week and fill their remaining time with low-intensity work.

#training

Reassess Zone 2 training for VO2 max improvement

When following government guidelines of 150 minutes of cardio per week, 40% of people doing only Zone 2 training will not see an increase in their VO2 max.