Shorten Your Cardio Time Even More with REHIT – Ulrich Dempfle with Dave Asprey – #834

You can earn 2 more years of lifespan in 12 weeks: 3 workouts a week at 3 times intensity for less than 10 minutes.

Cardio sometimes gets a bad rap; people either do too much or too little.

You’ve likely heard of HIIT (High Intensity Interval Training). In this episode of Bulletproof Radio, you’ll learn about the benefits of REHIT (Reduced Exertion High Intensity Interval Training) to improve cardiovascular fitness.

Ulrich Dempfle, co-founder of CAROL, joins me on the show to talk about REHIT and the science behind how you can get fit in less than 9 minutes. Yes, really.

The CAROL bike is founded on REHIT principles and gets right to the sweet spot for your health and fitness with added AI programming.

Decades of progressive research going back to the 1970s looked at high intensity training. New studies specifically show that by riding a CAROL bike you can:

  • improve your fitness by 12 percent in 8 weeks, measured by V02max. This adds two years of healthy lifespan!
  • lower your risk of Type II Diabetes by 60% in 8 weeks
  • burn twice as many calories minute-per-minute compared to traditional exercise. And keep burning calories for several hours after your ride.

“Anything that’s longer than 20 seconds and anything that’s longer than two times of 20 seconds is not maximum intensity because you couldn’t do maximum intensity for these sustained periods,” Ulrich says. “So, your slope and the change in intensity is just much lower on these traditional forms of HIIT.”

The idea for the stationary CAROL bike came alive in 2012 during work on chronic disease management programs for people with diabetes. Not surprisingly, researchers found it challenging to get people to exercise. The main excuse for most people was lack of time and frustration about slow results.

CAROL solves that. The bike’s core ride lasts 8 minutes and 40 seconds. It’s a gentle-paced ride with two 20-second sprints. On the sprints, you go all out as hard as you can.

But this isn’t just a conversation about riding a bike. We cover the science of how rapid glycogen depletion triggers the release and activation of certain signaling molecules (AMPk and PGC-1a), which triggers mitochondrial biogenesis. And why maximum intensity sprints ‘saturate’ the signaling response mechanism.

“When you do those sprints, you increase the energy demand in your body very suddenly, about 100 times higher compared to rest,” Ulrich says.” With this spike in energy demand, the muscle just cannot use its usual source of fuel, which is either fat or sugar that it takes from the bloodstream”.

“Instead, it would have to burn what’s called muscular glycogen, so that is a storage form of sugar that is stored in the muscle itself. That’s the emergency reserve. With the exercise, we force the muscle to tap into those energy reserves, and that kicks off a cascade of molecular changes, of triggers, where certain signaling molecules are released that basically tell the body to get fitter and stronger.”

Enjoy! And get more resources at Dave.Asprey/podcasts.
Got a comment, idea or question for the podcast? Submit via this form.

Go to, use code DAVE to save $100

Oral Ozone:, use code ASPREY20 to save 20%
Solve Sitting, use code DAVE20 and get $20 off any standing desk
Keto Bread:, use code DAVE to purchase the $48 sample bundle + get FREE shipping if you’re one of the first to order

Dave Asprey and Upgrade Labs host a transformative 3-day event featuring thought-provoking keynotes and fully immersive experiences that push the limits of human advancement, performance and longevity. You will connect with the world’s most innovative minds in the field of human optimization and biohacking. Join the community, at the Hyatt Regency Orlando, Florida.

This quarterly subscription box gives you access to biohacking resources that can support you in achieving your health goals and unlocking your potential. Go to

Learn directly from Dave Asprey in his new membership group

Listen on Apple Podcasts or iTunesListen on Google Podcasts

Amazon Music

Follow Along with the Transcript

Shorten Your Cardio Time Even More with REHIT – Ulrich Dempfle with Dave Asprey – #834


Bulletproof Radio: Fast Fitness! 40 Seconds, 3 Times a Week – Lance Dalleck, Ph.D. – #657, Cut Your Cardio to 9 Minutes – CAR.O.L FIT AI – #615

Key Notes

  • This is something called REHIIT, Reduced Exertion High Intensity Interval Training, specifically for cardiovascular fitness. – 1:53
  • The concept of an all out sprint, like a short all out sprint to get good cardiovascular benefits, that was first developed by the Wingate Institute in Israel, and it’s called the Wingate Sprint.  – 4:25
  • With the exercise, we force the muscle to tap into those energy reserves, and that kicks off a cascade of molecular changes, of triggers, where certain signaling molecules are released that basically tell the body to get fitter and stronger.   – 6:28
  • We deplete glycogen, so this emergency energy reserve, by about 25% to 30%, and to achieve the same level of glycogen depletion, you would need to go running for about 45 minutes,  – 10:13
  • CAROL is your personal trainer, is your AI health coach who knows how far to push you, and what resistance to give you, and she coaches you through the exercise, and it’s hard, but it’s hard only for a very, very short period of time. – 12:47
  • People are not quite aware what the difference between HIIT and REHIIT is. HIIT or Tabata or interval is high intensity, REHIIT is really maximum intensity.  – 14:11
  • The principal benefits that people can really expect to get are fitness improvement, and that would be measured in terms of VO2 max, your cardiorespiratory fitness of 12% in about eight weeks. Now, 12% in VO2 max improvement, that’s a really big deal. That’s like adding two years of healthy life expectancy. – 17:09
  • When you do the math on that, Ulrich, it’s three and a half hours of total exercise time over eight weeks with the results of a 12% improved VO2 max. – 18:24
  • CAROL, basically, takes all the guesswork out. So, it’s fully automated and optimized for this exercise. The AI sets the resistance exactly to the right level for you. – 24:44
  • You can measure it quite daily what’s your risk of developing type 2 diabetes, and the risk for those participant dropped by 60%. – 29:08
  • You burn so few calories, your body heat goes up by so little that most people don’t even sweat, but what happens then afterwards is that over an eight-hour period, your metabolism operates at an elevated level, and about 67% of the total calorie consumption from the exercise basically happens when you get off the bike. – 36:02
  • I’m a big fan of intermittent fasting or time-restricted eating or also doing five-day fast from time to time. I definitely still use the bike in those periods.  – 40:14
  • Do you see people combining this with stretching, with yoga? Is there an order? Do you do this before or after other kinds of exercise, Ulrich, or is this just what you do?  – 43:01
  • We’re working at the moment, and that will come out in August for all those for whom eight minutes 40 seconds is definitely too long still.   – 44:27
  • One of your riders who’s 78 started riding the CAROL. What happened then because this something that can work very different ages?  – 49:50
  • By the way, guys, you can use code Dave, save an extra $100 because I ask any guest who comes on the show who has a product, “Hey, hook up our Bulletproof Radio listeners.”   – 55:01

If you like today’s episode, check us out on Apple Podcasts at and leave us a (hopefully) 5-star rating and a creative review.

Go check out my new book Super Human: The Bulletproof Plan to Age Backward and Maybe Even Live Forever and also “Game Changers“, “Headstrong” and “The Bulletproof Diet” on Amazon and consider leaving a review!

Want to help others reach their full potential? Check out the incredible Human Potential Coach Training program I set up with Dr. Mark Atkinson.

You may also like

Dave Asprey

Start hacking your way to better than standard performance and results.

Receive weekly biohacking tips and tech by becoming a Dave Asprey insider.

By sharing your email, you agree to our Terms of Service and Privacy Policy