Dr. Andrew Sellars sat down for a conversation with Anthony from the Roadman Cycling Podcast to discuss his experience with integrating respiratory training into endurance training protocols.
Check out the full podcast in audio form HERE
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Podcast summary and key points
For decades, cyclists have obsessed over legs, watts, lactate, and heart rate. But if you dig into the physiology, a different story emerges: for a large number of athletes, the true limiter isn’t in the legs or heart—it’s in the breathing system.
And here’s the craziest part: most riders have never trained it.
This idea was explored in a recent conversation with Dr. Andrew Sellars, a leading authority in biomarker-based training and respiratory physiology. The takeaways were eye-opening—not just for performance, but for health and longevity as well.
Why breathing holds you back before your legs do
At high intensity, your body produces energy rapidly. One of the byproducts of this process is carbon dioxide (CO₂). Most athletes assume they breathe harder to get more oxygen. That’s only half true. In reality, CO₂ clearance is the primary driver of your breathing rate during exercise.
When your respiratory system can’t keep up with CO₂ removal, your breathing rate shoots up uncontrollably, mechanics fall apart, and performance falls with it. That’s the sensation of “redlining”—but it isn’t your legs quitting. It’s your ventilation system failing to keep pace.
Most cyclists never train it directly, so it becomes the limiter long before the heart or legs are actually maxed out.
What dysfunctional breathing looks like
You might be dealing with a respiratory limitation if you notice:
- Your breathing rate spikes early in hard efforts
- You lose rhythm and control of your breath under load
- You gasp or shoulder-breathe instead of using the diaphragm
- You experience “air hunger” before leg fatigue
- You get post-ride chest tightness or irritation
- You’ve been told you might have “exercise-induced asthma”
Dr. Sellars noted that a lot of what gets labeled as asthma in athletes is actually just poor breathing mechanics—something that can be trained and fixed.
Nasal breathing isn’t a fad – it’s physics and physiology
Nasal breathing has gotten trendy thanks to James Nestor’s book Breath, but the performance benefits go deeper than calm vibes:
- It stimulates diaphragmatic recruitment
- It smooths airflow and reduces airway irritation
- It naturally regulates breathing rhythm
- It encourages better CO₂ tolerance
- It improves oxygen delivery through the Bohr effect
Even WorldTour riders are experimenting with nasal strips—not for aesthetics, but to maximize airflow and diaphragmatic engagement.
Respiratory training works — and we now have data
Dr. Sellars shared a 48-week study from France on pro cyclists using CO₂-regulated respiratory muscle training. Results:
- Tidal volume (breath size) increased 8–10%
- FTP improved by 6% on average
- Breathing mechanics became more efficient at every intensity
- Gains came without additional leg or heart strain
These were elite cyclists already near their genetic ceiling. Yet their performance improved simply by targeting the previously ignored bottleneck—the respiratory system.
The biggest advantage? You can train it without fatigue
Unlike threshold intervals or strength work, respiratory training can be done:
- At home
- Without muscular fatigue
- Without interfering with ride quality
You can literally train your breathing system at threshold while sitting on the couch watching Netflix. If your limiter is ventilation, this completely changes how you structure your training week. You can move the needle without burning matches.
Bonus benefit: breathing drives HRV and recovery
Slow, controlled breathing dramatically improves heart rate variability (HRV) by increasing something called respiratory sinus arrhythmia—the natural wave in heart rate tied to breathing rhythm. The fastest way to improve HRV isn’t a miracle supplement or gadget. It’s better breathing.
How to test yourself (no lab needed)
During a steady effort (Zone 2 or tempo), ask:
✅ Can I maintain a smooth rhythm?
✅ Can I keep cadence and effort while slowing my breathing?
✅ Can I nasal breathe at moderate intensity without panic?
✅ Do I lose breathing control when power ramps, or when recovering between intervals?
If you answered no to any of these, chances are your breathing is a limiter.
So why isn’t everyone doing this already?
Simple: until recently, it was impossible to train breathing safely without messing up your chemistry. Hyperventilation drops CO₂ too low. Long breath holds push it too high. Both change blood pH and can cause dizziness, vasoconstriction, or worse.
That’s why CO₂-regulated systems like the Breathe Way Better (BWB) were developed—to let athletes safely push breathing intensity without compromising physiology. This is where respiratory training stops being a hack and becomes real training science.
The bottom line
You wouldn’t ignore leg strength or aerobic capacity, so why ignore your breathing system—the one thing you use in every second of training and racing?
Respiratory training:
✅ Improves power and threshold
✅ Delays fatigue
✅ Lowers perceived exertion
✅ Boosts HRV and recovery
✅ Enhances focus and calm under pressure
✅ Extends healthspan through better ventilation mechanics
It’s not hype. It’s physiology.
And the future of endurance training will include it—because it works.
Full Podcast Transcript
Most cyclists think their legs or heart are their biggest limiter.
But according to today’s guest, Dr. Andrew Sellars, the real bottleneck is something most riders have never trained: your breathing.
And the wild part is you can train it with minimal friction — even sitting on your couch.
0:18
Sitting at home on your couch.
This conversation blew my mind.
Dr. Andrew Sellars, welcome to the show.
Host: It’s an absolute pleasure to have you. Thanks for coming on. You’re one of the pioneers of biomarker-guided training. Can you share a bit about your background?
0:36 When did you first get interested in respiratory performance for athletes?
Dr. Sellars: This goes way back — I’m going to date myself here. I first heard an 8-track audio cassette on yoga breathing when I was a swim coach in a northern town in British Columbia, where I was paying my way through university coaching in the summers.
1:07 I was head coach of a fairly large team in a small town up north. One of my athletes brought me these 8-tracks and asked, “Is there any validity to this? It seems smart, but I don’t know what it’s worth.”
1:24 At the time I was studying physiology, so I had some biomechanics and physiology under my belt. The tapes introduced nasal breathing and the idea of slow breathing during running.
1:46 I was a budding triathlete, 19 years old, right at the early wave of triathlon — around 1989–1990. I started slow-breathing run training. Initially, I could barely go from a walk to a jog without increasing my breathing rate. The program was: slow your breathing and see how fast you can go while keeping it slow.
2:05 Over six weeks I went from running ~6:30 per kilometer to just over 4:00/km with the same slow-breathing pattern.
2:32 I thought, “This is brilliant.” I went back to the athlete who gave me the tapes and said, “I don’t know how this affects swimming — where breathing is time-limited — but let’s try it.”
2:47 We introduced slow-breathing patterns in swim training and saw good results. The deeper understanding of why it worked came years later, but that was the start — when I was 19, in Quesnel.
Host: Before podcasts I’ll often ride and research the guest, then end up asking different questions based on lived experience.
3:31 I had one of those today. I’m using TimeWear — the new respiratory shirt that measures breathing. I was lucky to get an early unit. My phone’s mounted to my bars since they haven’t integrated with Hammerhead yet, so I’m just using the TimeWear app.
3:52 One thing I noticed: when I was eating — I’m trying to fuel at ~80 g carbs/hr — mostly Haribo jellies — my breathing rate changed and my RPE shifted. That got me curious about what’s actually happening.
Dr. Sellars: A few things could be going on.
4:28 For those who don’t know, TimeWear is a shirt that measures respiratory pattern. It’s quite good at respiratory frequency and gives a reasonable estimate of tidal volume. It’s not lab-grade volumetry, but it’s excellent for patterns.
4:47 Awareness is the first step to training. We can talk later about how to adjust breathing to improve performance.
5:06 On Haribo — I heard you mention carbs on a podcast. I’ve used them for years in places like Mallorca because they’re easy to find. I carry a small bag on long rides to get me through the final hour.
Host: So what’s the thread from those first tapes to working with top performers? What patterns made you zero in on the breath?
5:52
Dr. Sellars: I have lots of stories. In that little northern town lived the smartest physiologist I’ve met — a Swiss coach/scientist who became a mentor.
6:08 He’d been involved with the Swiss sports schools, moved to Quesnel to raise a family, and ended up coaching some of Canada’s best cyclists, including Ryder Hesjedal and Geoff Kabush in their development years.
6:43 Years later, during medical school, I did a rural placement back in Quesnel mainly to spend time learning from him.
7:49 He brought me the first respiratory training device I’d seen, from Switzerland — the SpiroTiger, developed by his old colleagues. “I don’t know if this works,” he said. “Can you help me figure it out?”
8:04 It claimed to let you rebreathe CO₂ and train the respiratory system safely. I took it into the OR, hooked it to our CO₂ and O₂ analyzers and a pulse oximeter, and used it.
8:35 It did what it said: it maintained CO₂ in a safe physiologic range and alarmed when outside it. I didn’t know the internal math, but that’s why it was expensive — it actively managed CO₂. This was 1998–1999.
9:07 We started respiratory training. It was incorporated with Kabush and Hesjedal as youths, and the Swiss MTB team used it as well. Studies followed.
Host: For fans who’ve only heard two things about breathing — the carbon rebreather “scandal” stories and James Nestor’s Breath — can you fill in the blanks on what we’re actually talking about and why it’s powerful for cyclists?
10:23
Dr. Sellars: Cycling power output emerges from multiple systems: cardiac, respiratory, muscular, neurologic, psychologic, and metabolic.
10:59 Any one can be a strength or a limiter. A broken leg is an obvious musculoskeletal limiter. Less obvious: respiratory limiters.
12:02 You must pull O₂ from air into blood (lungs), pump it (heart), and extract it in muscle (metabolism). My view — borne out by research — is that respiration can be a key limiter. Train it, and you move the bottleneck.
Host: Without a lab, how can a regular rider baseline whether breathing is a limiter?
13:12
Dr. Sellars: It’s not trivial, but you can get far with awareness. Track breathing frequency and breath size across intensities. Everyone breathes slower at rest and faster as intensity rises — partly to bring in O₂, but primarily to blow off CO₂, the main driver of ventilation.
14:11 Most people don’t realize CO₂ drives the urge to breathe. Hold your breath with a pulse oximeter on: your O₂ saturation may stay high for a while, but your CO₂ rises, creating a powerful drive to breathe.
Host: In Wim Hof sessions you hyperventilate, then do long breath holds. You feel tingling and cold extremities. Is that CO₂ buildup?
14:46
Dr. Sellars: The over-breathing phase lowers CO₂ (hypocapnia), which lets you hold longer before CO₂ becomes uncomfortable. Hypocapnia also triggers vasoconstriction; during the hold, CO₂ rises, leading to vasodilation. The tingling is that vascular shift.
16:13 It’s real physiology. Hof doesn’t focus on mechanisms, but the effects are consistent with the science.
Host: I’ll never frame those sessions the same way again.
Dr. Sellars: If you liked Nestor’s Breath, Patrick McKeown’s The Oxygen Advantage is also useful — though it could be called the CO₂ Advantage, since tolerating slightly higher CO₂ has benefits when done safely.
Host: You developed a respiratory muscle trainer with Luke Way — the Breathe Way Better (BWB). What is it?
18:41
Dr. Sellars: Luke was an XTERRA athlete who came to Kelowna to coach with us at Balance Point Racing. He wanted to build something beyond coaching. There are three co-founders: Luke (coaching lead), me (physiology), and Alex (engineering).
19:45 We built a device that allows controlled rebreathed CO₂ to keep physiology in a normal pH range, so you can train breathing hard and long without the downsides of hyperventilation or the need to thrash your legs to simulate race-level ventilation.
Host (ad read): [Sponsor message omitted for brevity.]
Host: If breathing is your limiter, you can simulate the ventilatory load of a threshold session on the couch while watching Netflix — without hammering your legs.
22:13
Dr. Sellars: Exactly. If breathing is the limiter — and for many athletes it is — you can train it at threshold intensity without taxing legs or heart. Then you’re fresher for a six-hour ride the next day.
22:54
Host: One of my favorite workouts is 4-minute uphill intervals, 20 seconds on / 10 seconds off (Tabata style).
Dr. Sellars: Those sessions drive ventilation. When your breathing gives out, power drops. Train breathing for six weeks and you can often do more work before the respiratory system becomes the limiter.
Host: We’ve seen nasal strips in the WorldTour. Should we differentiate nasal vs. mouth breathing?
23:27
Dr. Sellars: Yes. Nasal breathing has several benefits. Less discussed is neural coupling: airflow through one nostril can stimulate the contralateral hemidiaphragm, promoting diaphragmatic involvement.
24:17 Nasal strips mainly open the airway, which matters when athletes are moving huge volumes of air. There’s also some bronchodilation downstream. Many riders feel smoother airflow and less irritation.
Host: I’ve had a broken nose since childhood. Patches change my breathing a lot.
Dr. Sellars: With a device like VO2 Master you can see tidal volume and frequency change in real time when riders incorporate nasal breathing.
Host: I’ve heard whispers that shaving nostril hair to “open the airway” increased infection rates for some teams. Is nasal hair a filter?
25:37
Dr. Sellars: Absolutely. Nasal hair and mucus help filter dust, smoke, bacteria, and viruses. I won’t comment on specifics, but from first principles, removing filters reduces filtration.
26:34 The nasal passages also warm and smooth airflow. One pattern we teach is slower frequency, larger breaths. Through the nose, airflow is smoother and less irritating.
27:12 At max intensity, everyone loses control of rhythm and drifts toward dysfunctional hyperventilation. That “ground-glass” irritation post-race is turbulent airflow. In velodromes you feel it a lot.
28:09 Many cases labeled “exercise-induced asthma” are actually dysfunctional breathing. Slow, controlled nasal breathing often reduces symptoms dramatically.
Host: If someone starts protocols today, what gains can they realistically expect — VO₂max, threshold, sprint, endurance?
28:35
Dr. Sellars: Everyone we’ve coached has included respiratory training. Studies across sports — short-track speed skating, cross-country skiing, swimming — show performance improvements.
29:39 A 2024 French study by Cyril Ritchie used our device for 48 weeks with pro cyclists and saw 8–10% improvements in breathing dynamics (tidal volume up; e.g., from ~6.8–7.0 L to ~7.5–7.7 L) and an average ~6% increase in FTP — in already elite riders.
30:51 Several Tour riders used the protocol leading into the race. Names were anonymized, but the effects were clear.
Host: What did the protocol look like?
31:26
Dr. Sellars: He progressed every six weeks:
- Weeks 1–6: Fundamentals — diaphragmatic control, nasal breathing, slow-breathing patterns at varied intensities.
- Weeks 7–12: Coordination — higher-frequency breathing drills.
- Weeks 13–18: Resistance breathing work.
- Weeks 19–24: Integration in time-trial/TT position.
…and continued cycling the emphases across the 48 weeks, building capacity (big breaths) and speed (move air fast under control), with as much nasal breathing as feasible.
Host: Any biomarker effects like HRV?
32:30
Dr. Sellars: HRV is strongly influenced by breathing. Slower breathing increases respiratory sinus arrhythmia — inhale increases venous return and stretch, augmenting stroke volume and often reducing the need for the very next beat, which raises beat-to-beat variability.
33:46 Wrist-based HRV can be noisy; a conscious, standardized measurement is better. But even noisy devices can show trends that correlate with sleep and load.
Host (ad read): [Sponsor message omitted for brevity.]
Host: Will respiratory analysis become as common as power meters? Where are we in the adoption curve?
37:10
Dr. Sellars: Think heart-rate monitors. Once measurement became easy and affordable, adoption exploded — even if many people didn’t use the data well.
37:54 We used an early strap called the BioHarness that tracked breathing and HR. Now multiple companies capture chest excursion and frequency accurately.
38:43 In a few years, most straps will display breathing metrics. A subset will use that data (often with AI-guided coaching) to adjust training and recovery. They should: breathing and HR are physiology, power is output.
39:21 We also need to update vocabulary — from LT1/LT2 to VT1/VT2 (ventilatory thresholds). The carb conversation is a useful parallel: fueling “for the work required” made people realize you can over-do carbs and create a “toll-booth” backlog. Similarly, we’ll refine how we “dose” ventilation.
40:32 Companies like TimeWear are making measurement accessible. Our training device is intentionally inexpensive because it’s both a teaching and training tool.
41:20 Beyond performance, breathing health matters for longevity. Recent work highlights VO₂ as a top predictor of lifespan, and ventilatory capacity/coordination may predict outcomes even better.
Host: The VO₂ literature is often weight-normalized, which you can “game.” I’m healthier at 80 kg than 68 kg, but my VO₂/kg looks better when I’m lighter.
42:00
Dr. Sellars: Agreed. Many scientists prefer absolute VO₂ (L/min) for that reason. If you’re healthier at 80 kg, your absolute VO₂ may be higher, even if the per-kg number is lower. Same story as watts vs. W/kg.
43:17 I recently rode with Sven Tuft — a big engine. We climbed 20% gravel grades; he was floating at what had to be ~500 W. The man’s physiology is incredible.
43:55 There aren’t many flat roads in BC — it’s all climbs.
Host: Andrew, I know you’re busy. I’d love to go deeper in a Part 2 or 3 in the coming weeks. There’s real tailwind behind respiratory training right now, and these conversations help peel back layers and build nuance.
44:31
Dr. Sellars: Absolute pleasure. Great to meet you, and thanks for having me on.
