Intro

This chapter introduces the innovative concept of re-hit training, showcasing its ability to deliver substantial fitness benefits in a shorter timeframe compared to traditional cardio. It highlights the research supporting this method, which provides a practical solution for individuals facing challenges in maintaining regular exercise amidst their busy schedules.

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Episode notes

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Upgrade, Dave Asprey sits down with Ulrich Dempfle, German-trained engineer and co-founder of CAROL Bike, to dismantle outdated cardio advice and introduce the 5-minute protocol that’s obliterating fitness myths.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• Why Zone 2 cardio is outdated advice for most people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/