The Aerobic Edge

Most runners have tried to fix their form at some point. Push off harder, use your glutes, land under your hips. It feels awkward, it feels harder, and after a week you go back to how you always ran.

In this episode of The Aerobic Edge I talk with Fredrik Zillén, a running technique specialist from Stockholm who has filmed runners with 3D motion-capture cameras in his studio since 2014, from people coming off the couch to national-team athletes. His view: a heavy landing or a short stride is usually a consequence of something happening higher up in the body, so that is where he starts.

In this episode

• Why trying to push off harder can work against you, and what your glutes are actually doing near toe-off
• The muscle Fredrik would train if you could only train one
• Where your speed goes when you get tired, and as you get older
• Why a good technique change should feel easier right away
• Why the same pace can feel so different on a treadmill
• How to run downhill faster without wrecking your quads
• What you can check yourself with just a phone

Chapters
00:00 How Fredrik got into running technique
07:30 Who walks into his studio
11:05 Power from the hip and core
15:50 What he sees in the first four seconds
18:35 Same knee, two ways of running
22:15 Running technique as a dance
33:45 Why engineers struggle with running form
36:40 Cadence, energy and pace
38:25 Push-off and the glutes
48:10 The soleus: the muscle for distance runners
53:25 Film yourself
56:55 Getting tired, getting older
59:55 Why the treadmill feels different
65:05 Downhill running
72:30 Where to find Fredrik

About Fredrik Zillén
Running technique specialist based in Stockholm. Former journalist, athletics coach since his teens, and full-time running biomechanics coach since 2010.
Website and online course: fredrikzillen.com
YouTube: Fredrik Zillén – Running Technique Specialist
Disclosure: I have taken Fredrik's online course myself.

Train with me
I coach recreational runners one-on-one, mostly for the half and full marathon. We build your aerobic base first, then add speed, with your easy running guided by heart rate.
Book a free 30-minute call · pacebuddies.com

Tymewear
A chest strap that measures your breathing as well as your heart rate, so you can see your thresholds without a lab. I'm an affiliate partner, and I only work with products I believe in.
tymewear.com/PACEBUDDIESTW · Code: PACEBUDDIESTW

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Fredrik's views come from his coaching practice and his own measurements. Some of the studies he mentions, including the treadmill environment and feedback studies, we could not verify. This episode is for education, not medical advice. If you have pain, see a qualified professional.

Two-time Olympic champion Alistair Brownlee on why easy runs should be truly easy, why he thinks hard sessions are only the icing on the cake, and how he learned to simplify fueling after a tough race in Kona.

In this episode:

• Alistair's path from age-8 triathlete to Olympic gold, including finishing 12th in Beijing
• Why he ran easy at 5:00/km while running a 28-minute 10K, and his view on volume and dose-response
• Why he thinks many amateurs do too little easy training and don't make it easy enough
• His view of hard sessions as the "icing on a small cake"
• Heat training: how he got into it, how he thinks it works, the risks, and why you should never do it alone
• How recreational runners can think about core temperature
• Simplifying fueling: practice it at least five times at race intensity and race rate
• Hydration and sodium: weigh yourself before and after, and what Alistair does and doesn't replace

Links:⁠True Fuels⁠ (Alistair's own brand)

⁠My conversation with Arnar Lárusson about training by ventilation⁠⁠

Get Tymewear⁠ (coupon code: PACEBUDDIESTW)

The advice in this conversation is Alistair's personal view as a former professional athlete. It is not medical advice. Ask a professional before you change your training or fueling.

Disclosure: I'm a Tymewear affiliate and may earn a commission if you buy through my link.

⁠Download the free Super Base starter plan

Chapters:

0:46 Alistair's Start in Triathlon
2:53 Three Olympics: From 12th in Beijing to Gold
5:21 Aerobic Base: Easy Runs That Are Truly Easy
7:48 How Much of Training Was Hard?
8:38 Why Slowing Down Is Hard and Key
10:06 How Alistair Judged "Easy"
11:45 Hard Sessions Are the Icing on the Cake
13:52 A Word About Tymewear
15:05 The Pyramid and Consistency
15:32 Training for the Ironman
17:38 Heat Training: Where It Started
19:51 How Heat Training Works
22:09 Heat Training for Hot Races
24:32 Heat Illness and Knowing When to Stop
26:01 Practical Ways to Heat Train
27:50 Monitoring Core Temperature
30:42 True Fuels and Core Control
32:55 Alistair's Experience With Core Control
35:10 Staying Cool on Race Day
38:15 Kona Ironman: What Went Wrong With Fueling
41:22 Practice Your Fueling Five Times
42:57 Hydration and Sodium
47:52 Building a Fueling Plan Into Marathon Training
50:40 Alistair Today
51:56 Where to Find Alistair

About Alistair Brownlee: two-time Olympic triathlon champion (London 2012 and Rio 2016), professional athlete for 18 years and founder of the sports nutrition brand True Fuels.

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 Arnar
• What VT1 and VT2 mean for fuel use, CO2 and your training zones
• Why heart rate can drift while ventilation stays steady (Arnar's example comes from cycling research)
• Lactate versus ventilation as a window into your effort
• How VT1 and VT2 are measured, and why the talk test is unreliable for finding VT1
• How to use VT1 for easy runs and VT2 for marathon-pace work
• How 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 Joost
Want 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 eating
• 00:30 Intro
• 01:48 Trent's background
• 04:00 Why Trent studies under-fuelling
• 06:30 Pregnancy, breastfeeding and under-fuelling
• 10:17 Overtraining vs REDs
• 14:01 A quick word about Pace Buddies
• 15:42 18 out of 21: what old overtraining studies missed
• 19:48 What energy availability actually is
• 22:38 Spring classics: bad race days, fine weekly average
• 25:31 Why you shouldn't calculate it yourself
• 28:57 Fasted running: risk and reward
• 31:52 Race weight and the weight-loss trap
• 34:30 The symptom list
• 39:14 How under-fuelling causes stress fractures
• 42:20 What a runner can actually do
• 47:20 Why your watch is off by 30%
• 49:48 Why the diagnostic tool ignores energy intake
• 51:47 One calorie per kilo per kilometre
• 55:30 How long does recovery take?
• 57:28 REDs and eating disorders are not the same
• 59:19 The study he'd run with unlimited funding

The 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 rationale
• 2023 IOC consensus statement on REDs
• Low energy availability and bone injury in elite distance runners
• More of Trent's work on PubMed

Find Trent
Women's Health and Sport Performance Institute (Boston) · Canadian Sport Institute Pacific (Victoria)

Disclosure
Trent 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 fail
• Morning pain as a baseline — settled versus fluctuating
• Why pain-free during the run tells you less than the next morning
• The runner whose foot wouldn't settle until they counted their steps at work
• What he does when rehab gets skipped, or a race no longer fits the timeline
• Where his job as a coach ends and a clinician's begins

Mark 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 nothing
• The three stages of iron deficiency — and where you can still intervene
• Why the duration of your run matters more than the intensity
• Hepcidin: the hormone that blocks iron absorption for hours after training
• The thirty-minute window after a run when absorption is best
• Why "100mg" on a supplement bottle is often 20mg of what counts
• Ferrous sulphate vs bisglycinate — and what the evidence actually supports
• What happens to your iron across a hard training block or at altitude
• Home ferritin tests, and why she's not ready to recommend them yet
• How 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.

Chapters
01:00 From ballet to iron research
02:00 What iron does in the body
05:00 Ferritin, haemoglobin and the three stages
08:00 How iron is absorbed — and what blocks it
11:30 Who's most at risk
16:30 Hepcidin: why training blocks absorption
20:00 The window after your run
23:30 Low carb, keto and iron
25:00 Haem vs non-haem, and vitamin C
32:00 Can you have too much iron?
34:30 Supplement forms
37:00 Symptoms, and why fatigue is a poor signal
39:30 How often to get screened
40:30 Home ferritin tests
43:00 Hard training blocks and altitude
47:00 Dosing: elemental iron, timing and alternate days
54:00 What she'd study next

Find Dr Alannah McKay
LinkedIn: linkedin.com/in/alannah-mckay
ACU profile and email: acu.edu.au
Google 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