You’ve probably heard of HIIT—but have you heard of “REHIT?” This isn’t just another workout trend...it’s a new science-backed way to train with maximum efficiency and zero wasted time. If you’re still jogging, you’re wasting hours for minimal results.

In this episode of The Human Upgrade, Dave Asprey sits down with Ulrich Dempfle, German-trained engineer and co-founder of CAROL Bike, to dismantle outdated cardio advice and introduce the 5-minute protocol that’s obliterating fitness myths.

Forget the treadmill grind. REHIT (Reduced Exertion High-Intensity Training) exercising delivers:

• 12% VO₂ max increase

• 6x the fitness gains of daily jogging

• 62% drop in diabetes risk

• 5x more BDNF for brain power

—all with just 8 minutes of effort per week.

But was it? Ulrich unpacks the hard data, crushes the Zone 2 obsession, and shows how a brand-new way of exercising is giving explosive results—no matter your age or fitness level.

What You’ll Learn in This Episode:

• Why Zone 2 cardio is outdated advice for most people

• The science of REHIT and how 2 sprints beat 2-hour workouts

• The shocking data on VO₂ max, insulin sensitivity, and lifespan

• How CAROL uses AI to personalize exercise for any age or ability

• Why most people fail at fitness—and how to fix it

• The real role of lactate, BDNF, and HRV in recovery and resilience

• How perimenopausal women benefit more from REHIT than HIIT or jogging

• Why adherence—not intensity—is the #1 predictor of results

• What to do when you’re traveling or don’t have access to the tech

Resources:

• Dave Asprey’s New Book - Heavily Meditated: https://daveasprey.com/heavily-meditated/

• CAROL Bike Website and use code ‘DAVE’ for a discount – https://carolbike.com/

• CAROL Bike Instagram - https://www.instagram.com/thecarolbike/?hl=en

• 2025 Biohacking Conference: https://biohackingconference.com/2025

• Danger Coffee: https://dangercoffee.com

• Dave Asprey’s Website: https://daveasprey.com

• Dave Asprey’s Linktree: https://linktr.ee/daveasprey

• Upgrade Collective – Join The Human Upgrade Podcast Live: https://www.ourupgradecollective.com

• Own an Upgrade Labs: https://ownanupgradelabs.com

• Upgrade Labs: https://upgradelabs.com

• 40 Years of Zen – Neurofeedback Training for Advanced Cognitive Enhancement: https://40yearsofzen.com

Timestamps:

• 00:00 Introduction to REHIT Training

• 00:24 Meet Ulrich Dempfle: The Mind Behind CAROL Bike

• 00:51 The Science and Benefits of REHIT

• 01:44 Comparing Traditional Cardio to REHIT

• 02:32 Dave Asprey’s Personal Fitness Journey

• 03:43 The Efficiency of REHIT Training

• 05:03 Practical Applications and Accessibility of REHIT

• 08:22 Addressing Common Concerns and Misconceptions

• 11:25 The Future of Fitness: REHIT and Beyond

• 18:29 Scientific Validation and Real-World Results

• 31:53 Clinical Trials and Tech Integration

• 32:06 Upgrade Labs and CAROL Bike

• 33:00 Mitochondrial Effectiveness and Insulin Sensitivity

• 36:05 Zone Two Training vs. High-Intensity Training

• 42:02 REHIT for Perimenopausal Women

• 48:18 AI and Personalized Exercise

• 57:52 Lactate and Exercise Benefits

• 01:01:48 Interval Walking Training

• 01:04:01 Conclusion and Future Insights

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