#216 VO2 Max, Zone 2 Training, HRV Wearables, Sauna, and Evidence-Based Performance Supplements with Brady Holmer

Dr. Mike Hart interviews elite runner Brady Holmer about endurance training, VO2 max physiology, and common misconceptions. Holmer explains that zone 2 builds the aerobic base and enables high training volume with less fatigue, notes heart-rate zones are ideally defined by lactate thresholds, and says he primarily uses perceived exertion rather than lactate or heart rate during training. He advises against guiding workouts by wearable HRV scores, arguing accurate HRV requires standardized morning measurements and that wearable data can create a nocebo effect; trends may be informative, but subjective feel should come first. They discuss polarized vs pyramidal training and typical 80/20 intensity distributions, effective session durations, mechanisms limiting VO2 max (central vs peripheral), and why Norwegian 4x4 intervals work by maximizing time near 85–90% max heart rate. They cover breathing/nose breathing, inspiratory muscle training, sauna/hot baths as performance adjuncts, nutrition timing of carbohydrates, and supplements including beetroot, beta-alanine, urolithin A, and post-exercise ketones.

Brady Holmer is an endurance-focused performance expert and elite runner whose work explores the science and practice of aerobic fitness, VO2 max, recovery, and smarter cardio training. In this episode, he explains how zone 2 training builds the foundation for endurance, why HRV and wearable data should be interpreted carefully, and how protocols like Norwegian 4x4 can improve performance when used in the right context. Through a blend of long-term training experience, research literacy, and practical coaching insight, Holmer helps listeners better understand how to train harder, recover smarter, and think more clearly about what actually improves cardiovascular fitness.

Training & Cardio

Zone 2 Cardio

Overview (Cleveland Clinic): https://health.clevelandclinic.org/zone-2-cardio

Lactate / Threshold-Based Training

Threshold zones review (PMC): https://pmc.ncbi.nlm.nih.gov/articles/PMC6537749/

Lactate-guided threshold interval training (PMC): https://pmc.ncbi.nlm.nih.gov/articles/PMC10000870/

Norwegian 4x4

Classic VO2 max paper (PubMed): https://pubmed.ncbi.nlm.nih.gov/17414804/

4x4 protocol heart-rate response study (PMC): https://pmc.ncbi.nlm.nih.gov/articles/PMC7399937/

Polarized Training

Meta-analysis / review (PubMed): https://pubmed.ncbi.nlm.nih.gov/38717713/

Older landmark paper (PubMed): https://pubmed.ncbi.nlm.nih.gov/24550842/

Pyramidal Training

Pyramidal vs. polarized study (PMC): https://pmc.ncbi.nlm.nih.gov/articles/PMC9299127/

HRV & Wearables

Marco Altini

Official site: https://www.marcoaltini.com/

HRV4Training: https://www.hrv4training.com/

HRV Measurement / Use

HRV4Training article with Marco Altini: https://www.hrv4training.com/blog2/heart-rate-variability-hrv-training-with-dr-marco-altini-how-to-exercise-using-hrv

Oura Ring

Official: https://ouraring.com/

WHOOP

Official: https://www.whoop.com/

Experts & Writing

Dr. Andy Galpin

Official site: https://www.andygalpin.com/

Brady Holmer

Substack profile: https://substack.com/@bradyholmer

Physiologically Speaking: https://www.physiologicallyspeaking.com/

Supplements & Recovery

Exercise / Performance Supplements

NIH overview: https://ods.od.nih.gov/factsheets/ExerciseAndAthleticPerformance-HealthProfessional/

Creatine

Cleveland Clinic overview: https://my.clevelandclinic.org/health/treatments/17674-creatine

Beta-Alanine

NIH consumer overview: https://ods.od.nih.gov/factsheets/ExerciseAndAthleticPerformance-Consumer/

ISSN position stand (PMC): https://pmc.ncbi.nlm.nih.gov/articles/PMC4501114/

Beetroot / Dietary Nitrate

Review (PMC): https://pmc.ncbi.nlm.nih.gov/articles/PMC4008816/

Meta-analysis (PubMed): https://pubmed.ncbi.nlm.nih.gov/23580439/

Urolithin A

Mitopure / official: https://www.mitopure.com/

Altitude training camp study (PMC): https://pmc.ncbi.nlm.nih.gov/articles/PMC12628386/

Exogenous Ketones

Ketone-IQ official: https://ketone.com/

Post-exercise ketone monoester and EPO study (PubMed): https://pubmed.ncbi.nlm.nih.gov/36449571/

Post-exercise ketones improved endurance training adaptations study (PubMed): https://pubmed.ncbi.nlm.nih.gov/41757674/

Show Notes

00:00 HRV Training Myth

00:59 Zone Two Benefits

02:11 Finding True Zone Two

03:59 RPE Over Wearables

06:27 HRV Done Right

12:06 80 20 Training Split

15:23 Zone Two Session Length

18:37 Cardio Adaptation Science

24:03 Norwegian 4x4 Explained

30:30 Sports Versus Machines

32:54 Leg Day Timing Tips

34:58 Best Leg Exercises

38:21 Nordic Curl Reality Check

39:11 Portable Nordic Setup Tips

39:51 Biggest Running Mistake

40:18 Nose Breathing Zone Two

42:16 Breathing Tools And Myths

43:08 Inspiratory Muscle Training

44:51 How Much Benefit Really

46:27 Sauna For VO2 Max

48:35 Heat Mimics Altitude

50:59 Sauna Fertility Debate

52:54 Red Light Therapy Reality

54:30 Carbs Fuel The Work

56:25 Timing Carbs Around Training

57:52 Best Carb Food Choices

59:41 Supplements For Cardio

01:00:20 Creatine Beta Alanine Beetroot

01:02:16 Urolithin A Breakthrough

01:05:01 Ketones After Training

01:07:31 Other Supplements And Caffeine

01:09:07 SARMs Peptides And Doping

01:10:10 VO2 Max And Longevity

01:10:49 Wrap Up And Where To Follow

The Hart2Heart podcast is hosted by family physician Dr. Michael Hart, who is dedicated to cutting through the noise and uncovering the most effective strategies for optimizing health, longevity, and peak performance.

This podcast dives deep into evidence-based approaches to hormone balance, peptides, sleep optimization, nutrition, psychedelics, supplements, exercise protocols, leveraging sunlight, and de-prescribing pharmaceuticals — using medications only when absolutely necessary.

Beyond health science, we explore the intersection of public health and politics, exposing how policy decisions shape our health landscape and what actionable steps people can take to reclaim control over their well-being.

Guests range from out-of-the-box thinking physicians such as Dr. Casey Means (author of "Good Energy") and Dr. Roger Sehult (Medcram lectures) to public health experts such as Dr. Jay Bhattacharya (Director of the National Institutes of Health (NIH) and Dr. Marty Mckary

(Commissioner of the Food and Drug Administration (FDA) and high-profile names such as

Zuby and Mark Sisson (Primal Blueprint and Primal Kitchen).

If you're ready to take control of your health and performance, this podcast is for you.We cut through the jargon and deliver practical, no-BS advice that you can implement in your daily life, empowering you to make positive changes for your well-being.

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