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How accurate are training zones built on a percentage of max heart rate or VO2max? In this episode, Arnar Lárusson, founder of Tymewear, explains why he thinks those zones can land in the wrong place, what VT1 and VT2 are, and how ventilation can be used to guide training. In this episode: Why percentage-based zones can put you in the wrong zone, according to ArnarWhat VT1 and VT2 mean for fuel use, CO2 and your training zonesWhy heart rate can drift while ventilation stays steady (Arnar's example comes from cycling research)Lactate versus ventilation as a window into your effortHow VT1 and VT2 are measured, and why the talk test is unreliable for finding VT1How to use VT1 for easy runs and VT2 for marathon-pace workHow fast Arnar's users report progress after changing their zones (4 to 12 weeks, anecdotal)5:34 Engineering Meets Physiology 8:55 Why Ventilation Matters for Runners 15:09 Why % of Max Zones Miss VT1 and VT2 19:12 Personalizing Your Training Zones 26:20 Ventilation vs. Heart-Rate Drift 31:41 Lactate vs. Ventilation 35:45 Measuring VT1 and VT2 39:46 Practical Training with Ventilation 54:30 How Fast Can You Improve? 57:49 What's Next for Tymewear? About Arnar Lárusson: founder of Tymewear, a chest strap that measures heart rate and breathing. Background in mechanical engineering, including prosthetics and exosuits. Links: Get Tymewear (coupon code: PACEBUDDIESTW) Tymewear on YouTube Tymewear on Instagram Note: the figures in this conversation (non-responder rates, sensor validation, fatigue data) are Arnar's own claims. Check the research yourself before changing your training. Disclosure: I'm a Tymewear affiliate and may earn a commission if you buy through my link. Download the free Super Base starter plan

Not overtrained – under-fuelled? Dr Trent Stellingwerff, a lead author of the IOC's REDs clinical assessment tool, explains the signs to watch for and what to do about them. Your easy runs feel hard, you're getting sick more often and your sessions are inconsistent. The usual advice: you're overtrained, back off. Trent thinks that advice is often wrong. In his team's review of the classic overtraining studies, 18 of the 21 that reported nutrition showed an energy or carbohydrate shortfall during the overload period. We cover what energy availability is, why the diagnostic tool doesn't measure it, symptoms you can spot without a lab, how under-fuelling leads to stress fractures, and the one simple equation worth knowing. Free 30-minute call with JoostWant a coach to look at your training and fuelling with you? Book a free 30-minute call at Pace Buddies, online running coaching for recreational runners. We'll talk through your goals, your current training and what's getting in the way.Book your free call · pacebuddies.com Timestamps 00:00 Cold open: a month of not eating00:30 Intro01:48 Trent's background04:00 Why Trent studies under-fuelling06:30 Pregnancy, breastfeeding and under-fuelling10:17 Overtraining vs REDs14:01 A quick word about Pace Buddies15:42 18 out of 21: what old overtraining studies missed19:48 What energy availability actually is22:38 Spring classics: bad race days, fine weekly average25:31 Why you shouldn't calculate it yourself28:57 Fasted running: risk and reward31:52 Race weight and the weight-loss trap34:30 The symptom list39:14 How under-fuelling causes stress fractures42:20 What a runner can actually do47:20 Why your watch is off by 30%49:48 Why the diagnostic tool ignores energy intake51:47 One calorie per kilo per kilometre55:30 How long does recovery take?57:28 REDs and eating disorders are not the same59:19 The study he'd run with unlimited fundingThe quick version Energy availability = energy intake minus the energy cost of training, corrected for fat-free mass. It is not the same as a calorie deficit: one low day is fine, the pattern is the problem.Rough cost of a run: 1 kcal per kg body weight per km. It dates from the 1960s, was built on a flat treadmill, and falls apart on hills and when walking.Don't try to measure your way out: watch and app calories can be off by about 30%. Watch the symptoms instead.First step: add roughly 300–400 kcal of carbohydrate around training, spread food across the day, and see how you feel after a week.Key papers Overtraining vs REDs: shared pathways, symptoms and complexities (the 18-of-21 review)IOC REDs Clinical Assessment Tool (CAT2): scientific rationale2023 IOC consensus statement on REDsLow energy availability and bone injury in elite distance runnersMore of Trent's work on PubMedFind TrentWomen's Health and Sport Performance Institute (Boston) · Canadian Sport Institute Pacific (Victoria) DisclosureTrent previously spent six years in R&D at PowerBar (Nestlé Research Center) and has no current commercial interest in anything discussed. This episode touches on eating disorders. REDs and eating disorders overlap but are not the same thing. Nothing here is medical advice or a diagnostic tool. If several of the symptoms sound familiar, see a physician.

You've done the rehab. The exercises feel fine. But running still doesn't — and nobody seems to own that part of the process. Irish running coach Mark O'Mahony works with recreational runners in exactly that gap: sometimes alongside a physio, sometimes long after one has signed them off. He came to running sideways — he fought Muay Thai professionally, then finished a hundred-mile race on seven weeks of training, which he does not recommend. He won't hand out a list of exercises, and he explains why. What he gives instead is the layer underneath: how he reads pain as information, why morning stiffness is his main signal, what he does when someone's response is worse than expected, and why he only ever changes one thing at a time. In this episode: Why the gap between doing the exercise and handling running is where comebacks failMorning pain as a baseline — settled versus fluctuatingWhy pain-free during the run tells you less than the next morningThe runner whose foot wouldn't settle until they counted their steps at workWhat he does when rehab gets skipped, or a race no longer fits the timelineWhere his job as a coach ends and a clinician's beginsMark is a coach, not a clinician, and he's clear about that line throughout. Nothing in this episode is medical advice. If something isn't improving, get it looked at. Find Mark coachmarkomahony.com Instagram: @mark_omahony_running About Pace Buddies I'm Joost, a running coach working with recreational marathon runners — mostly people fitting real training around a job and a family. Aerobic-first, and adjusted to how your body is actually responding rather than to what the calendar says. Free 30-minute call, no pitch: cal.eu/pacebuddies/freecall Coaching and training plans: pacebuddies.com

Most runners who think they have low iron have never had the right test. And most who supplement for it never needed to. Dr Alannah McKay is a Senior Lecturer at the Mary MacKillop Institute for Health Research, Australian Catholic University, where she studies iron metabolism in athletes. She trained full-time as a ballet dancer from twelve to eighteen and thinks she was iron deficient through most of it — never tested, never treated. Her PhD, done in partnership with the Australian Institute of Sport, was awarded the Dean's List honour, and she now works alongside Professor Louise Burke on female athlete physiology. In this episode: What ferritin actually measures, and why a haemoglobin test alone tells you almost nothingThe three stages of iron deficiency — and where you can still interveneWhy the duration of your run matters more than the intensityHepcidin: the hormone that blocks iron absorption for hours after trainingThe thirty-minute window after a run when absorption is bestWhy "100mg" on a supplement bottle is often 20mg of what countsFerrous sulphate vs bisglycinate — and what the evidence actually supportsWhat happens to your iron across a hard training block or at altitudeHome ferritin tests, and why she's not ready to recommend them yetHow often a recreational runner should realistically get screened ⚠️ Educational only — not medical advice. Supplementing iron without testing carries real risk, including for people with undiagnosed haemochromatosis. Talk to your doctor before changing anything. Chapters01:00 From ballet to iron research02:00 What iron does in the body05:00 Ferritin, haemoglobin and the three stages08:00 How iron is absorbed — and what blocks it11:30 Who's most at risk16:30 Hepcidin: why training blocks absorption20:00 The window after your run23:30 Low carb, keto and iron25:00 Haem vs non-haem, and vitamin C32:00 Can you have too much iron?34:30 Supplement forms37:00 Symptoms, and why fatigue is a poor signal39:30 How often to get screened40:30 Home ferritin tests43:00 Hard training blocks and altitude47:00 Dosing: elemental iron, timing and alternate days54:00 What she'd study next Find Dr Alannah McKayLinkedIn: linkedin.com/in/alannah-mckayACU profile and email: acu.edu.auGoogle Scholar: scholar.google.com Book a free 30-minute call I'm Joost, running coach at Pace Buddies. I coach recreational runners using an aerobic-first approach — building the engine properly before layering speed on top, instead of the other way round. If this episode left you wondering whether something in your own training is holding you back, book a free thirty-minute call. No pitch deck, no pressure. We look at what you're actually doing now, where the gaps are, and whether coaching would help — and if it wouldn't, I'll tell you that. Book your free call at pacebuddies.com The Aerobic Edge is an evidence-based endurance podcast for recreational runners. New episodes with researchers, coaches and athletes who actually know what they're talking about. Follow the show so you don't miss the next one. Instagram: @pace.buddies

Every fuelling guide tells you to take as many grams per hour as your gut can handle. Prof. Tim Noakes has spent four years arguing the number you actually need is closer to ten. His position is contested. Prof. Louise Burke argues the opposite, and they published a three-part debate against each other in the American Journal of Clinical Nutrition in May 2026 — her case, his case, and a joint consensus. All linked below. Tim Noakes is emeritus professor at the University of Cape Town, author of Lore of Running, and has been in the field since 1976 as both researcher and runner. His 2026 Endocrine Reviews paper works through 160+ studies to argue that endurance performance is limited by blood glucose and the brain monitoring it, not by muscle glycogen. We go back further than the paper: the day in December 2010 he changed his mind about carbohydrate, what it cost him, his own type 2 diabetes diagnosis despite decades of marathons, and the graph he'd shown hundreds of times without noticing what was in it. Also: what hypoglycemia actually feels like and why it reverses in ten minutes, what "low carb" means in real grams, fat oxidation above 1.5 g/min, industry funding in sports nutrition, and what any of it means at 40 to 50k a week. THE PAPERSEndocrine Reviews review: https://doi.org/10.1210/endrev/bnaf038The 10 g/h triathlete trial: https://doi.org/10.1152/ajpcell.00583.2024 THE BURKE DEBATE (Am J Clin Nutr, May 2026)Burke — Yes: https://doi.org/10.1016/j.ajcnut.2026.101268Noakes — No: https://doi.org/10.1016/j.ajcnut.2026.101269Joint consensus: https://doi.org/10.1016/j.ajcnut.2026.101271 Prof. Noakes co-founded Nutrition Network and The Noakes Foundation, both built around low-carbohydrate nutrition — discussed openly in the episode. For information only, not medical advice. ABOUTThe Aerobic Edge is an evidence-based endurance running podcast hosted by Joost, running coach at Pace Buddies. Aerobic-first marathon coaching for recreational runners. Book a free 30 min consultation on: https://pacebuddies.com

There comes a point in a race where it stops being about fitness. Deena Kastor — Olympic marathon bronze medallist and American record holder for nineteen years — is unusually specific about what to do when that moment arrives. We cover where her mental training started under coach Joe Vigil, the hill where she changed the words in her own head, and the practices she kept for decades:a daily gratitude list, and building joy into the sessions she dreaded. She also explains what an easy run is supposed to feel like (her Kenyan teammates called it a massage), how she handles start-line nerves with three memorised reasons she should succeed, and what she does in the last third of a marathon when it starts to fall apart. She also pushes back on the usual line about comparison, and on what to prioritise when you get injured. 0:00 Intro 1:53 Who Deena Kastor is 5:22 Where the mental training started 10:57 What an easy run should feel like 16:09 Building joy into your week 27:02 Reframing disappointment 33:29 Start-line nerves 36:11 The last third of a race 44:01 Comparison 48:21 Injury 55:01 One takeaway Book: Let Your Mind Run. Instagram: @deenakastor Website: deena-kastor.com Coaching: pacebuddies.com

Most runners assume nasal breathing works because it gets you more oxygen. It doesn't — and today's guest explains what's actually going on instead. Zack Kramer, a strength and conditioning coach who rebuilt his practice around breathwork after years in CrossFit, walks through the real mechanism behind nose vs. mouth breathing: it's not oxygen uptake, it's CO2 tolerance.We cover what functional breathing actually looks like day-to-day, why mouth breathing becomes a hidden habit for so many runners, how to train your diaphragm like any other muscle, and a simple pre-run warm-up that speeds up nasal adaptation. Zack also shares his own month-long transition to full-time nasal breathing — including what didn't work.KEY TAKEAWAYS1. Nasal breathing isn't about getting more oxygen in — runners are already near-saturated (95%+). It's about CO2 tolerance, which delays the urge to breathe harder at a given pace.2. Nasal adaptation typically takes about a month of consistent practice; committing fully (24/7, including sleep) speeds it up.3. The diaphragm is a trainable muscle — a tired diaphragm pulls oxygen-rich blood away from your legs and arms before it pulls from anywhere else.4. A short CO2-buildup warm-up (exhale breath holds, ~2 minutes) can shortcut the rough first 5–10 minutes of a run.5. Chronic nasal issues (deviated septum, congestion) are common and manageable with nasal dilators — full nasal breathing isn't an all-or-nothing requirement.* Website / coaching: http://athletebreathcoaching.com* Instagram: https://www.instagram.com/athletebreathcoach/PaceBuddiesWebsite / coaching: http://pacebuddies.com* Instagram: https://www.instagram.com/pace.buddies/* Strava: @pace.buddies Chapters 00:00 Episode preview00:38 Welcome & Zack's background — football to CrossFit to breathwork03:36 Breathwork courses that shaped his approach (Oxygen Advantage, XPT)05:20 What is functional breathing?07:33 Why nasal breathing is so hard to maintain09:46 Why nasal breathing matters — filtration & nervous system14:21 CO2 tolerance introduced15:39 What CO2 actually is, and why tolerance matters18:57 Does CO2 tolerance improve performance?21:31 Adaptation period & living with chronic nasal congestion22:10 Nasal dilators — show and tell25:43 Where to start with a runner28:25 How long does nasal adaptation actually take?30:35 Running with low-intensity nasal breathing problems34:42 The oxygen myth — debunking "mouth breathing = more energy"36:04 Training your diaphragm like a muscle39:03 Why a tired diaphragm steals blood from your legs40:31 Gear demo: the Breather Fit device42:46 Gear demo: the Isocapnic device43:44 How to actually use the devices — sets, reps, progression46:18 Breath training during intervals and rest periods48:12 The pre-run warm-up that speeds up adaptation52:27 Breathing for relaxation and recovery55:09 365-degree breathing technique58:25 How to practice belly, back, and side expansion59:17 Where to find Zack & closing

Most runners try to fix their form by chasing numbers — 180 steps per minute, a midfoot landing, a shorter stride. Paul Mackinnon thinks that's the wrong end of the problem.Paul runs The Balanced Runner in Melbourne and has spent close to a decade coaching running technique full time, working with Olympians like Galen Rupp and Brett Robinson alongside recreational runners with sore knees. His argument: cadence and foot strike aren't settings you adjust. They're outcomes of how the rest of your body moves. So he starts at the top — the arms and torso — and lets the legs reorganise underneath.We get into where the 180 rule actually came from, why forcing a foot strike can move an injury rather than fix it, and how he uses an old way / new way comparison so runners can feel a change instead of being told about it.I did a session with Paul before recording this, so some of what you'll hear I felt myself.Paul Mackinnon* Website: https://tbrunner.com* Instagram: https://instagram.com/thebalancedrunnerJoost Dekker — Pace Buddies* Website: https://pacebuddies.com* Free 30-minute consultation: http://pacebuddies.comChapters00:00 Intro00:54 From field hockey to running technique03:04 Canberra, dirt trails, and feet that sounded different04:53 Why physics has to come first06:40 What a first session actually looks like09:11 Feel it before you change it10:33 A word from Pace Buddies11:08 Why top-down instead of chasing cadence12:28 The arm swing: where it starts14:39 How arms change your foot strike17:59 What a good arm swing feels like20:15 Elbows, not hands22:29 Letting the athlete make the choice23:22 Old way, new way26:37 One cue at a time31:11 How long before it becomes a habit34:03 Better is better37:11 Does technique make you faster?39:36 The 800m data, clarified40:51 The 180 cadence rule44:18 Stride length and cadence are two levers47:27 Why your watch data doesn't tell the whole story49:28 Heel, midfoot, forefoot — does it matter?53:49 How to spot overstriding yourself55:59 Where to find Paul1:00:39 Outro

For a hundred years, runners have blamed "lactic acid" for burning legs and fatigue. It's one of the most persistent myths in sport — and it's wrong.In this episode I talk with Dr. Michael Lindinger, exercise physiologist and former professor at the University of Guelph, who spent decades studying what actually happens to lactate and acid in working muscle. We get into what lactate really is (a fuel your muscles, heart, and brain burn — not a waste product), where the burning sensation actually comes from, why the soreness days after a marathon has nothing to do with lactate, and what "clearing lactate" really means for your training.If you've ever been told your legs were full of lactic acid, this conversation will change how you think about fatigue — and about what your interval sessions are actually building.Note: Dr. Lindinger works in the nutraceutical field; this is disclosed where supplements are discussed.----------------------------------------CHAPTERS 01:48 — Who is Dr. Michael Lindinger03:12 — What lactate actually is (and the 1930s myth)05:34 — The infusion study: lactate as fuel, not waste06:42 — Lactate as an oral supplement and the glucose-sparing effect08:44 — Lactate fuels the whole body — even the brain09:49 — A word from Pace Buddies10:22 — Where lactate is made, and why "anaerobic" is the wrong word12:37 — What really causes fatigue: potassium, sodium, phosphate13:32 — The phosphocreatine system: instant but short-lived16:15 — The burning sensation — cytokines, not lactate19:25 — Why the last 3K of a marathon burns (and it isn't lactate)20:27 — Post-race soreness: damage and inflammation, not lactate21:57 — What "clearing lactate" means when lactate rises23:41 — Fat burning, and why lactate is always being produced24:25 — How the whole body buffers and reuses lactate26:19 — Hitting the wall: running out of glucose27:32 — How fast the body clears lactate after hard efforts29:55 — Hydrogen ions, acidosis, and why lactate isn't "lactic acid"33:43 — Can you train lactate clearing?37:21 — Fast-twitch vs slow-twitch: where the burn happens39:03 — Do buffers work? Bicarbonate, beta-alanine 42:18 — The massage therapist myth43:21 — "Clearing lactate" in plain terms: what training really builds

Dr. Jose Antonio, co-founder and CEO of the International Society of Sports Nutrition (ISSN), joins The Aerobic Edge to go through what the evidence actually says about protein, buffering supplements, and caffeine for endurance athletes.We cover why the protein-kidney myth persists despite years of contrary data, why most national protein guidelines are too low for anyone trying to race rather than just finish, and why sodium bicarbonate — historically avoided for its GI side effects — deserves a place next to beta-alanine, creatine, nitrate, and caffeine as a serious performance supplement.We also get into the practical side: how to fit more protein into a training day without overhauling your diet, when supplementation timing actually matters and when it's just convenience, and why endurance athletes underestimate how much a central, brain-driven sense of fatigue shapes race-day performance. 00:34 – Origins of the ISSN06:04 – Debunking the protein-kidney myth14:03 – How much protein you actually need20:38 – Amino acids vs. protein shakes33:07 – The six supplements with real evidence behind them34:32 – Sodium bicarbonate as a performance buffer42:09 – Caffeine dosing and timing44:56 – Central fatigue and race-day mindset54:55 – Nitrate/beetroot juice59:20 – Where to find Jose Antonio Guest Links Instagram: @supphdISSN Instagram: @THE_ISSNISSN Annual Conference: Jupiter, Florida, every June Want a structured, evidence-based approach to your own training? I coach recreational runners toward their personal best, building real aerobic fitness that shows up on race day. Book a free 30-minute consultation call at pacebuddies.com.

Your HRV dropped after a hard session. Most runners take that as proof they trained hard. Marco Altini says it's proof of the opposite. Marco is the founder of HRV4Training, an advisor at Oura, and an endurance coach. He came to physiology the long way round — from computer science and early wearable prototypes, back to university to study sports science, because he wanted to understand the bodies he was measuring. In this conversation we cover what HRV actually measures, why "higher is better" is wrong, how to build your normal range, morning vs night measurement, what to change when your baseline drops, why a falling HRV in taper week is the good news, and why the data should make you need the data less. Find Marco on Substack, where he writes about HRV, training and coaching. Want structured, evidence-based coaching? Book a free 30-minute call at pacebuddies.com Find Marco: HRV for Training AppMarco Altini - Personal Website

What if the pain in your knee, your Achilles or your foot has almost nothing to do with the spot that hurts? In this episode of The Aerobic Edge, I sit down with movement specialist Helen Hall — the person runners often turn to as a last resort, after they've tried everything and been told they might never run again. Using one of the most advanced motion analysis systems in the world (affectionately known as Doris), Helen has spent decades uncovering why repetitive injuries keep coming back. Her core message is deceptively simple: most injuries below the waist have their root cause above the waist — in your head and shoulders — or in your feet. Pain shows up where your body works hardest, but that's rarely where the problem actually begins. We start with the head. Helen walks through what a forward-leaning head really does to your body: at 15 degrees it effectively weighs around 12 kilos, at 30 degrees roughly 18, at 45 degrees about 22. That's not a strength problem — as Helen puts it, there isn't a weak sinew in your body. It's a massive energy leak, and your hardest-working joints pay the price. From there we get practical: how to use nothing more than your phone to see your own posture honestly, her wall exercise for finding true upright (which I try live on the recording), and why "upright and at ease" feels like leaning back to almost everyone. Then one of my favourite parts: the arm swing. Helen invented a cue she calls the lemme — a figure-of-eight, the sideways infinity symbol. She shows the difference between pumping your elbows (which roots you to the spot) and rolling the shoulder girdle in that figure-of-eight (which sends you forward, opens your stride and makes you lighter on your feet). We also cover walk-run strategy — including a runner in her sixties who ran a 4:19 marathon off almost no training — and go deep on feet: Morton's neuroma, numb toes, and a remarkably simple foot-wiping habit that helped one barefoot marathoner drop from 5.5 hours to 5 hours with no other training. A quick note: Helen demonstrates several of these exercises on camera. If you're listening to the audio, you'll be missing those visuals — so for the movements, I'd recommend watching the video version on YouTube. What you'll learn: Why pain below the waist usually starts above it What a forward head really costs you — energy leak, not weakness How to check your posture with just your phone The wall exercise for finding true upright The lemme: how a figure-of-eight arm swing opens your stride Why walk-run can make you faster, not slower How to wake up "asleep" feet with a simple daily habit About Helen Hall: Movement specialist and author. Her second book, The Smooth Runner: 20 Ways to More Speed for Less Effort, is on the way. Find Helen: Website: helen-hall.co.uk Instagram: https://www.instagram.com/helenhallpfm/ Connect with Pace Buddies / The Aerobic Edge: Website: pacebuddies.com Book a free call: cal.eu/pacebuddies/freecall If you enjoyed this, follow The Aerobic Edge and share it with a runner who keeps fighting the same injury.

Erin Carson: Mobility, Strength & Moving Better for Life | The Aerobic Edge What does it really take to stay strong, mobile, and injury-free as a runner — not just for your next race, but for the rest of your life? In this episode I sit down with Erin Carson, strength coach behind some of the best endurance athletes in the world, including ultra-running GOAT Courtney Dauwalter. Based in Boulder, Colorado, Erin has built a unique niche at the intersection of strength, mobility, and endurance performance. Her approach is refreshingly holistic: it's never just about muscle, but about the nervous system, fascia, posture, and even mood and freedom of movement. We start with Erin's journey from Division One basketball in Canada to becoming a sought-after strength coach in the endurance world, and why her background shaped a "train the person for what they actually want to do" philosophy. From there we get into the practical stuff every runner and triathlete can use: Why a strength coach is so focused on mobility — and why mobility is not the same as flexibilityThe three key areas of mobility that anchor everything: ankles, hips, and the thoracic spine (and how a knee problem often starts somewhere else entirely)A simple at-home self-test for your pelvis and hamstrings, and why "tight hamstrings" usually aren't the real problemWhy most running injuries happen on the landing — not the push-off — and why this gets worse running downhillWhat "training age" means, and where beginners should actually start with strength workWhy you should evaluate your strength program by how you run, not how you compare to everyone else in the gymHow to train effectively at home with minimal equipment — adjustable dumbbells, bands, and a stability ballWhy understanding the "why" behind each exercise matters more than mindlessly following a listStaying strong in the final third of a race, when posture and form start to break downStrength, mobility, and quality of life as we age — and why your daily choices today shape your final decadeWhether you're training for your first marathon or chasing a personal best, this conversation will change how you think about strength and movement — on the road and in everyday life. 🔗 Find Erin Carson:Website: ecfitstrength.com YouTube: Mobility Monday — new every MondayInstagram: ecfit_strength 🎧 The Aerobic Edge PodcastHosted by Joost Dekker, founder of Pace Buddies.Helping recreational runners train smarter through aerobic development, movement quality, and injury prevention. If you enjoyed this episode, follow the show, leave a review, and share it with a running friend who could use it. Got a question or topic you'd like covered? Reach out — I'd love to hear from you. PaceBuddies.com

In this episode I sit down with Professor Paul Laursen — sport scientist, co-author of Science and Application of High-Intensity Interval Training, and co-founder of Athletica — to break down the science of endurance in plain language. From mitochondria and fat-burning to HIIT, the neuromuscular system, nutrition, recovery and HRV, we turn the biology of running into practical tools to help you train smarter, recover better, and avoid the classic pitfalls. ABOUT PAUL LAURSENA sport physiologist from British Columbia, Canada, with a career spanning the Australian Institute of Sport and the New Zealand Olympic program, where he led physiology across two Olympic cycles. He's best known for his work on high-intensity interval training, co-authored the leading textbook on the subject, is co-writing the fifth edition of Lore of Running with Tim Noakes, and co-founded the AI training platform Athletica. WHAT WE COVER How muscles create movement and turn food into energyMitochondria: why endurance training grows them, and why fat is the clean fuelThe heart as a muscle — stroke volume and why running starts to feel easierWhy "no pain, no gain" is the number-one endurance mistakeConsistency over heroics: the most important session is the next oneBuilding the aerobic base first (Paul's fat-burning study with Stephen Seiler)MAF and low-heart-rate training, with a nod to Phil MaffetoneNutrition as a lever: insulin, whole foods, and the simple PFC ruleWhen to add HIIT, and how it recruits fast-twitch fibresThe neuromuscular system and Dr. Marius Bakken's Norwegian MethodWhat adaptation is and when it happens: sleep, recovery and nutritionReading your body's data: wearables, RPE, feel and HRVUnderstanding HRV: 7-day vs 60-day averages and overtraining riskKEY TAKEAWAYS Fat is your clean fuel — aerobic training teaches your body to burn it efficientlyPatience beats punishment — build the base before adding intensityRecovery is training — prioritise sleep, then whole-food nutritionListen to the trend, not the day — use HRV to adjust before stress builds LINKSPaul Laursen: https://www.paullaursen.comHIIT Science: https://www.hiitscience.comAthletica: https://www.athletica.ai MENTIONEDScience and Application of High-Intensity Interval Training — Laursen & BuchheitLore of Running (5th edition, with Tim Noakes)The Norwegian Method Applied — Dr. Marius Bakken PACE BUDDIESWebsite: https://pacebuddies.comBook a free call: https://cal.eu/pacebuddies/freecall Enjoyed this episode? Subscribe to The Aerobic Edge and leave a review — it helps more runners find the show.

In this episode of The Aerobic Edge, coach John Starrett ("The Stable Master") returns for a deep dive into the sub-3 marathon — a magical barrier for many runners. Since 2017, John has coached a staggering 962 runners to sub-3 and 274 to sub-2:30, all online. We unpack what it actually takes to break that barrier and what your training needs to look like to get there. John explains why his approach centers on temporal flow — his own term for fatigue resistance — and why the old story about lactic acid and H ions is outdated. Lactate isn't the enemy but fuel; the skill lies in shuttling and reusing it. We work through his complete system, from pre-super base to the marathon block, and he shares the exact key sessions that reveal whether your sub-3 fitness is right where it needs to be. He also speaks candidly about his own comeback: after five or six years away from running, he's starting from the bottom again with run-walk intervals, with Joost as his coach. An honest look at consistency, progression, and structure — the pillars of his philosophy. In this episode: Why 962 runners hit sub-3: system over isolated workoutsTemporal flow & fatigue resistance: the science beyond lactic acid and H ionsThe key sessions 3-5 weeks out (16/18 miles at marathon pace) that tell you if it's "on"Why John aims for 2:55 fitness to buffer against heat and conditionsRace tactics: stay slightly off pace until 32K, then make your move in the final 10KBridge training: the difference between a sub-4 and a sub-3 runnerDisguised marathon pace: endurance spine runs vs. structural runs (80' & 90' tempos)Lactate tickles & blend workouts: safely touching 5K/10K pace without injuryA look at his Olympic athlete (18 miles at 5:10/mile) and what it reveals about the systemJohn's own comeback: from zero to pre-super base via run-walkAbout John Starrett: online marathon coach with a track record in sub-3 and sub-2:30, known for his emphasis on consistency, progression, and structure over "old school" hard training and exhausting VO2max sessions.