Flex Diet Podcast

Jonah Rosner is a sport scientist, performance coach, and founder of Marathon Science, translating endurance research for runners and hybrid athletes.
Does everyone really need two to three hours of Zone 2 each week? Sport scientist Jonah Rosner joins Dr. Mike T Nelson to explore when higher-intensity work makes sense, how to separate cardiovascular stress from tissue stress, and what heat training and blood flow restriction may add to an endurance plan.
Expect to learn why time-crunched lifters may benefit from carefully selected intervals, how to separate cardiovascular load from tissue load, why sprinting needs a gradual runway, what heat acclimation may change beyond plasma volume, where oxygen strategies and blood flow restriction fit, and how to interpret heart rate alongside performance, and much more.
Connect with Jonah:
Marathon Science newsletter
Instagram: @rosnerperformance
Episodes you’ll enjoy next:
VO2 Max, Zone 2 Training & the Psychology of Human Performance — Ben Skutnik — #402
From Powerlifter to Trail Runner — Paul Oneid & Cody Miller — #393
Episode Timestamps:
03:00 Zone 2 Versus HIIT
05:00 Choosing Safer HIIT Modes
08:56 Building Toward Faster Sprints
13:30 Quality Density Running Repeats
15:48 Polarizing Your Running Training
19:36 Heat Training For Endurance
26:40 Exercising In The Heat
29:48 Cooling And Heat Perception
32:27 Cold Water Between Intervals
35:10 Altitude And Oxygen Strategies
40:35 Exercise With Oxygen Therapy
42:16 Blood Flow Restriction Training
45:10 Measuring Muscle Oxygen Extraction
52:04 Heart Rate Versus Output
57:26 Triphasic Training For Runners
61:25 Thinking Beyond Training Dogma

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James de Lacey is a strength and conditioning coach with an MSc in Sport & Exercise Science and more than a decade of experience in professional sport spanning professional and international rugby/rugby league. He now focuses on combat sports to prepare fighters under Sweet Science of Fighting.
Do fighters really need zone 2 cardio? Strength and conditioning coach James de Lacey of Sweet Science of Fighting joins Dr. Mike T Nelson to challenge the "big aerobic base first" playbook for combat sports, from heart rate recovery and short-rest sprint intervals to muscle oxygen (NIRS) data. They also dig into VO2 max, wearables and why AI-written programs often miss the mark.
Expect to learn why James questions the “huge aerobic base” approach for fighters, how heart rate recovery and heart rate kinetics can reveal more than time in zones, how short-rest sprint intervals and a simple air bike baseline test can guide programming, what muscle oxygen (NIRS) data can and can’t tell you, why trends beat single data points from wearables, and why generic AI-written programs often miss the mark—and much more.
Connect with James:
sweetscienceoffighting.com
jamesdelacey.com
Sweet Science of Fighting on Instagram
Sweet Science of Fighting on YouTube
Episodes you'll enjoy next:
Episode 326: Row Hard, Breathe Easy: Boosting Aerobic Capacity with Dr. Kenneth Jay: Dr. Kenneth Jay on rowing and boosting aerobic capacity (Mike credits Dr. Jay for the bioenergetic testing he mentions in this conversation).
Episode 221: Training performance, nitric oxide, blood flow, and more via the NNOXX device with Evan Peikon: Evan Peikon on training performance, nitric oxide and blood flow via the NNOXX device (Mike mentions Evan in this conversation).
Episode Timestamps:
03:35 The biggest conditioning mistake in MMA
05:50 Why sprints are more aerobic than you think
07:46 Do fighters need a huge aerobic base?
09:44 VO2 max, muscle limits and oxygen testing
11:57 Conditioning trends and training volume
15:36 Zone 2, time costs and the 80/20 debate
22:10 Heart rate response and recovery between rounds
25:43 Mike’s rower test and heart rate recovery
28:25 Air bike sprints with short rests
31:44 Muscle oxygen and power between repeats
34:19 Testing and training each athlete’s limiter
41:47 Flexible Meathead Cardio and technical training
46:05 Elite athletes, VO2 max and training context
50:22 NIRS, oxygen drops and peak power
57:18 Why trends beat single test results
1:02:56 Wearables, coaching judgment and session design
1:06:57 AI programs and generic training blocks
1:13:02 Training around life and where to find James

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Bryan Krahn has been a personal trainer since 1997, a CSCS since 2005, and a full-time online coach since 2014. He is a fitness writer and the author of two books with Men's Health.
Will AI replace online coaches, or only the ones who stop being human? Veteran online coach and Men's Health author Bryan Krahn joins Dr. Mike T Nelson for a candid, unfiltered conversation about paying for expertise, whether coaches should disclose AI use, personal experiences with peptides and TRT (opinion, not advice), and Mike's simple rower-based cardio plan.
Expect to learn why paying for expertise makes you a better coach, how Bryan and Mike use (and distrust) AI in coaching and writing, whether coaches should disclose their AI use, why stacking compounds makes personal experiments hard to interpret, how Bryan thinks about TRT and lab markers like HDL, LDL and PSA, and Mike’s simple rower-based cardio plan—and much more.
Bryan and Mike discuss peptides, TRT and other compounds from personal experience and opinion. Nothing here is medical advice; talk to a qualified healthcare professional before changing any medication or supplement routine.
Connect with Bryan:
over50muscle.com
Bryan on Instagram (@bryankrahn)
Episodes you'll enjoy next:
Episode 137: Training Straight Talk with fitness writer, and online physique coach Bryan Krahn: Bryan's previous visit to the show: training straight talk from a fitness writer and online physique coach.
AI Disclosure, Deepfakes & the Death of Expertise — Dean Guedo & Jeb Stuart Johnston — #404: Dean Guedo and Jeb Stuart Johnston on AI disclosure, deepfakes and the death of expertise (Mike mentions Dean in this conversation).
Episode Timestamps:
02:25 Online coaching's catch-22: taking clients you may not be set up to help
04:16 Bryan's niche: from over-40 clients to the over-50 guy, and why parents and older dads fit
06:10 Edge-case clients, referral networks and paying peers for expertise
08:06 Why paying for consults still matters, including Bryan's 1999 consult with Charles Poliquin
11:35 Why AI still struggles with niche training questions: PEDs, zone two and the Thomas Inch dumbbell
17:03 AI inside coaching software, and why chatbots are so agreeable
18:53 Would clients be accountable to a bot, and will live coaches last?
23:48 Should coaches disclose AI use to clients? Everyday AI wins like soundbars and grill repair
27:29 Contest-prep coaches, AI photo checks, and why coaches get second opinions
34:32 Peptide offers and appetite-suppressing drugs: personal experiences, not advice
39:38 DNP stories and risks as the speakers recount them
42:34 Mitochondrial peptides, NAD+ and IV infusions: why stacked self-experiments are hard to interpret
49:39 TRT: dialing in the basics first and working with a physician
52:41 Lab markers: HDL, LDL and PSA, and changing the marker versus the outcome
58:37 Traveling with a TRT prescription: Bryan's border-security story
1:01:25 Mike's rower cardio plan: baseline 2K test, progressive six-minute sessions and a smarter four-by-four
1:10:58 Should writers disclose AI use? Beating the blank page without losing your voice
1:19:06 Wrap-up: coaching availability, training from 50 to 53, and where to find Bryan

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Dr. Gregory Kelly, N.D., is Chief Product Officer at Qualia Life, a naturopathic physician, author of Shape Shift, and former editor of Alternative Medicine Review.
Detox is more than a liver story—and it is not a juice cleanse. Dr. Gregory Kelly of Qualia Life explains how clearance pathways work together, why mobilizing stored chemicals is not the same as eliminating them, and the thinking behind Qualia 2-Day Detox.
Expect to learn why detox skepticism is warranted, how Dr. Kelly thinks about cumulative stress and chemical exposure, what liver biotransformation and elimination mean, why his formulation includes a between-meals binder stack, how sleep and the glymphatic system enter the conversation, and what Qualia’s small symptom-questionnaire study can and cannot establish—and much more.
Dr. Kelly discusses his company’s Qualia 2-Day Detox product. Product descriptions and health claims are his views, not independent verification or medical advice; the small study discussed used self-reported symptom questionnaires.
Connect with Greg:
Qualia on Facebook
Qualia on Instagram
Qualia on TikTok
Dr. Gregory Kelly on LinkedIn
Episodes you'll enjoy next:
Episode 352: Dr. Dan Pardi on Stem Cells, Supplements, and the Future of Health with Qualia: Dr. Dan Pardi on stem cells, supplements, cognitive performance and health habits at Qualia.
Episode 310: Unpacking the Science of Sleep with Dr. Allison Brager: Neuroscientist Dr. Allison Brager on sleep phases, circadian rhythms and performance.
Episode Timestamps:
05:03 Detox skepticism and why this conversation matters
06:35 Why Qualia chose to develop a detox product, according to Dr. Kelly
08:08 Who might need detox support, and Mike's experience with wildfire air pollution
09:42 Dr. Kelly's environmental medicine background and the "last straw" bucket analogy for stress load
12:44 Exposures Dr. Kelly tries to limit: canned foods, strong scents, new furniture, indoor air
15:59 Small, consistent changes versus one silver bullet; Dr. Kelly cites biomonitoring studies
18:59 Water filtration and drinking-water habits
21:32 Larger exposures, the precautionary principle, mold, and skin products
24:18 Sunscreen, sun exposure, and not overcomplicating health choices
28:39 How Qualia approached the formulation, and an explanation of phase one, two, and three liver pathways
33:07 Dr. Kelly's description of the four-step packets: morning and with-meal
36:28 The between-meals binder stack, and a weight-loss study Dr. Kelly cites on stored chemicals
40:26 The bedtime packet, the glymphatic system, and brain demands when learning new skills
44:35 Fat-loss phases, a two-days-a-month approach, and Qualia's small symptom-questionnaire study
48:49 Dr. Kelly's pairings for detox days: sauna, gentle movement, hydration, skin brushing, baths
54:24 Wrap-up: fitting the routine into your schedule, and where to find more information

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In this episode of the Flex Diet Podcast, I break down why I built the Physiologic Flexibility Certification (PhysFlex) as a “level two” continuation after you’ve already got the basics of nutrition, training, and recovery mostly dialed in. I explain how Phys Flex targets four overlapping homeostatic regulators—temperature (heat/cold exposure), pH (acidity/alkalinity shifts), expanded fuels (ketones and lactate), and oxygen/CO2 regulation (breathing)—and why taking a systems view matters more than treating everything in silos.
I share examples of how these pillars can become the real limiter in recovery and performance, including high-intensity work, long-duration events, and signs like elevated overnight respiration rate. Enrollment is open from Monday, October 12 through midnight PST Monday, October 19, 2026, and I’m offering direct email access for questions.
Enroll here: https://physiologic.miketnelson.com/sales
Episode Timestamps:
00:00 Welcome and Podcast Focus
00:19 Course Enrollment Window
01:44 Who This Certification Is For
02:48 Why Four Pillars Together
03:41 The Four Homeostatic Pillars
05:05 Systems Thinking Over Silos
08:07 Applying the Framework to Recovery
11:41 Course Structure and Interventions
13:09 Support, Email Access, Next Guest
13:58 Medical Disclaimer and Closing

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