You can have your training, nutrition, and supplement stack dialed in and still be neglecting the strongest predictor of how long and how well you live: your cardiovascular fitness. Low cardiorespiratory fitness has been linked to more avoidable deaths than smoking, obesity, and diabetes combined, yet lack of time remains the number one reason people skip the work that improves it.

We dive deeper into this in The Kris Gethin Podcast with Ulrich Dempfle, CEO and co-founder of CAROL Bike, breaking down how two 20-second sprints, done just a few times a week, can raise VO2 max and improve metabolic health. We also chat about whether cardio really kills muscle gains, why expensive biohacks cannot replace a strong cardiovascular base, and why Ulrich rates zone 2 training a 5 out of 10.

Ulrich Dempfle is the CEO and co-founder of CAROL Bike, the AI-powered exercise bike built on Reduced Exertion High-Intensity Interval Training (REHIT). A mechanical engineer by training and former McKinsey and PwC management consultant, he developed CAROL in collaboration with leading exercise scientists.

What's Discussed:

(9:08) Why the strongest predictor of healthspan is the one people skip most.

(14:50) Why low cardio fitness may be deadlier than smoking, obesity, and diabetes combined.

(15:53) Why mitochondrial peptides cannot replace the basics.

(17:42) How much VO2 max can improve in 8 to 20 weeks.

(23:58) What actually happens during two 20-second sprints.

(38:48) Why so many biohackers try to buy their way around the hard work.

(44:00) How your phone is costing you sleep.

(45:04) Calories, the afterburn, and where cardio fits in fat loss.

(48:29) GLP-1s and the skinny-fat trap.

(51:50) How short sprints improve blood sugar control and insulin sensitivity.

(57:37) Two sprints vs. 60 sprints: when more is not better.

(1:00:44) How to fit sprint cardio into a five-day lifting week.

(1:05:30) What to track to prove it is working.

(1:11:04) Rapid fire: cardio and muscle gains, zone 2, and VO2 max.

If you train hard, care about recovery, and want to see the tools, supplements, and products I personally recommend, head to krisgethin.com/pages/recommendations

To receive my free book, A Guide to Biohacking, leave an honest review on the platform where you listen to the podcast, then email a screenshot to info@krisgethin.com

Thank You to Our Sponsors!

CAROL Bike: Want a science-backed cardio workout that takes just five minutes? Head to carolbike.com/kris and use code KRIS for the best available offer.

Structured Water by Natural Action: Want to upgrade the quality of the water you drink every day? Head to naturalaction.com and use code KRIS at checkout.

Hydrogen Rich Water: Want an easy way to add molecular hydrogen to your hydration routine? Head to drinkhrw.com/pages/h2-in-sports and use code GETHIN for 10% off.

Find More From Kris Gethin:

Website: krisgethin.com/

Instagram: @krisgethin/

YouTube: youtube.com/krisgethin

2 Shred: unmatchedsupps.com/products/2shred

Find Out More About Ulrich Dempfle and CAROL Bike:

Website: carolbike.com

Instagram: @thecarolbike

YouTube: youtube.com/c/CAROLbike

Kris Gethin shares his personal journey and expert insights on how to effectively manage fat loss and maintain muscle after 40, emphasizing the importance of adapting strategies to biological changes.

Chapters

00:00 Introduction to Fat Loss Challenges After 40
02:24 Stress, Cortisol, and Fat Storage
04:36 Cellular Metabolism and Mitochondrial Health
06:33 Using Blood Glucose Monitoring for Better Results
07:01 Hormone Optimization Through Diet and Lifestyle
07:54 Sleep Optimization and Circadian Rhythms
08:20 Biohacking Techniques for Aging Gracefully
09:20 The Importance of Outdoor and Recreational Cardio
10:15 Adapting Strategies to Your Biological Feedback
10:43 Final Thoughts and Practical Advice for Over 40 Fitness

Resources

Carol Bike - uses artificial intelligence to personalize high-intensity workouts in real time, delivering an efficient, science-backed cardio session in just minutes.
Code: KRIS - save $300

Better Bodies / GASP — Performance-focused gym apparel and training gear that I have been wearing since 2005 - designed for serious lifters.
Code: KRIS15 — 15% off your order

Bahé Trainers — Comfortable running, training and hiking shoes featuring grounding/earthing technology designed to create an electrical connection with the earth.
Code: KRIS15 — 15% off your order

Nutrition Solutions — Prepared grass fed, humane raised, organic and antibiotic free meal solutions that make it easier to stay consistent with your nutrition when life gets busy. I have used them weekly since 2015
Code: LEGACY20 for your discount

Find More From Kris Gethin

Website: krisgethin.com/

Instagram: @krisgethin/

YouTube: youtube.com/krisgethin

Tik Tok: @krisgethin

You can have your training, nutrition, supplements, and recovery dialed in and still overlook one of the most powerful inputs your body receives every day: light. From the moment you wake up to the screens, LEDs, office lighting, and nighttime exposure around you, your light environment may influence your circadian rhythm, recovery, sleep, and performance.

In this episode, Alex Kikel and I break down how different wavelengths of light interact with the body, why morning and evening light matter, and where red and near-infrared light may fit into a performance-focused routine. We also look at what you can do for free, what is worth spending money on, and where biohacking starts becoming unnecessary overkill. The goal is simple: understand the mechanism, control the basics first, and use technology only when it actually adds something.

What's Discussed:

(12:47) Why light should matter for performance and body composition.

(19:14) Blue light, near-infrared light, and what your environment is missing.

(23:48) The simplest light protocol you can do for free.

(34:15) How light fits into fat loss, muscle, and recovery.

(42:46) Why the first few minutes of your morning matter.

(54:20) Why sleep supplements cannot fix a bad nighttime environment.

(57:08) Using red and near-infrared light around your workouts.

(1:06:45) Red light for skin, hair, and recovery protocols.

(1:13:35) Light habits: overrated or underrated.

(1:17:28) The $0, $100, and $10,000 light protocol.

(1:20:29) Why jumping straight to expensive biohacks can backfire.

If you train hard, care about recovery, and want to see the tools, supplements, and products I personally recommend, head to krisgethin.com/pages/recommendations

To receive my free book, A Guide to Biohacking, leave an honest review on the platform where you listen to the podcast, then email a screenshot to info@krisgethin.com

Thank You to Our Sponsors!

Structured Water by Natural Action: Want to upgrade the quality of the water you drink every day? Head to naturalaction.com and use code KRIS at checkout.

Hydrogen Rich Water: Want an easy way to add molecular hydrogen to your hydration routine? Head to drinkhrw.com/pages/h2-in-sports and use code GETHIN for 10% off.

Find More From Kris Gethin:

Website: krisgethin.com/

Instagram: @krisgethin/

YouTube: youtube.com/krisgethin

2 Shred: unmatchedsupps.com/products/2shred

Find Out More About Alex Kikel:

Website: theprepcoach.com/

Instagram:@alex_kikel

YouTube: @alexkikelTPC

TPC Army: skool.com/tpcarmy/about