Episode 374: Zone 2 Cardio: What the Science Really Says (Pros, Cons & Better Options) with Kristi Storoschuk

In this episode of the Flex Diet Podcast, I sit down with my friend Kristi Storoschuk, a PhD candidate in exercise physiology, to unpack her review paper on zone 2 cardio and what the evidence actually shows. We dig into what “zone 2” really means (including lactate thresholds and why common proxies like heart rate and the talk test can miss the mark), where the 80/20 endurance model came from, and why messaging around zone 2 for mitochondrial function, fat oxidation, metabolic flexibility, and health may be overstated, especially for the general population.

Kristi explains why higher intensities often produce equal or better mitochondrial and performance-related adaptations, how training volume and population context change the conversation, and where low-intensity work like walking may still fit.

Sponsors:

• Flex 4: Kristi's Top 4 tips for improving aerobic fitness as a recreational lifter: https://flex-diet.kit.com/17ac1beade
• Daily Fitness Insider Newsletter: https://flex-diet.kit.com/bfa1510fa8

Coming up:

• ISSN 2026: https://www.sportsnutritionsociety.org/

Available now:

• Grab a copy of the Triphasic Training II book I co-wrote with Cal Deitz here.

Episode Chapters:

• 04:04 Why Zone Two Went Viral
• 09:40 Defining Zone Two Lactate
• 14:15 Talk Test and Practical Limits
• 16:43 Does Zone Two Even Matter
• 21:08 The 80/20 Misapplied
• 26:14 Origins of Base Training
• 32:06 Mitochondria Volume vs Intensity
• 40:08 How Myths Persist Online
• 44:16 Zone Three Over Zone Two
• 44:46 Why Some Recover Faster
• 45:37 Overtraining Study Lessons
• 49:59 Listen To Output Signals
• 52:20 How Often To Train
• 54:42 Short Daily Progressives
• 57:46 Tabata Reality Check
• 01:00:19 Walking And Health Outcomes
• 01:05:23 Mitochondria Versus Performance
• 01:08:04 Lactate Threshold Beats VO2
• 01:12:43 Fueling And Final Wrap
• 01:14:33 Podcast Outro And Disclaimer

Flex Diet Podcasts you may enjoy:

• Episode 360: Exploring Aerobic Development & Concurrent Training with Jason Brown
  • YouTube: https://www.youtube.com/watch?v=lkqim0EDfec&t=4s
• Episode 269: From Mitochondria to Metabolic Health Insights with PhD Candidate Kristi Storoschuk
  • YouTube: https://www.youtube.com/watch?v=T9EFRluKt6Q

Connect with :

• Instagram: https://www.instagram.com/krististoroschuk/
• Website: https://krististoroschuk.com/

Get In Touch with Dr Mike:

• Instagram: Drmiketnelson
• YouTube: @flexdietcert
• Email: Miketnelson.com/contact-us

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