When Dr Andrew Sellars — the respiratory physiologist with 35 years of research in his field — was on the podcast, his framing on breathing was direct. Most amateur cyclists assume their performance limiter is the legs, the heart, or the lungs in general. Almost none consider the diaphragm and intercostal muscles specifically as trainable. And the evidence from his work and the French research he discussed is that for many cyclists, the respiratory muscles are the actual limiter, and training them produces FTP gains that the cyclist couldn't get from more interval work.
The detail is in the breathing techniques cycling performance guide. The headline finding is striking: 6% FTP gains over 48 weeks of structured respiratory training in already-trained professional cyclists. The protocol is 10 minutes daily. The cost is around $200 for the device. The trade-off for the cyclist whose legs feel fine but who blows up at threshold is enormous.
This article is the case for breathing as a training variable, the protocols that work, and the surprising overlap with sleep and recovery.
The Stanford experiment
When James Nestor was on the podcast — covered in the nasal vs mouth breathing for cycling episode — his Stanford experiment was the most striking single piece of evidence I've seen on breathing.
Nestor and a research partner blocked their noses for 10 days using surgical plugs, forcing them to mouth-breathe continuously. The measurements were dramatic:
- Blood pressure rose approximately 25 points within 48 hours.
- Sleep quality plummeted, deep sleep duration dropped substantially.
- Snoring increased dramatically.
- Resting heart rate elevated.
- Cognitive performance declined on standardised testing.
- All metrics returned to baseline within days of removing the plugs and resuming nasal breathing.
The 10-day experiment is unethical to replicate in a clinical trial, but the implication is clear. How you breathe matters substantially — and most adults aren't breathing optimally, especially during sleep when nasal breathing has the largest impact on recovery quality.
The cycling implication runs through every system the experiment measured. Sleep quality is the master recovery tool. Blood pressure regulation affects cardiac efficiency. CO2 tolerance affects performance at high intensity. All of these are downstream of the breathing pattern, and all of them are trainable.
Dr Sellars' 35-year picture
Sellars' research, covered in the respiratory training 6% FTP gains episode, builds on decades of inspiratory muscle training research originally developed for clinical populations with respiratory disease. Applied to elite athletes, the same training principles produce meaningful performance gains.
The mechanism: the diaphragm and intercostal muscles fatigue during sustained high-intensity exercise. As they fatigue, ventilatory efficiency drops. Less air moves with each breath. The cyclist who blows up at threshold isn't necessarily out of leg power — they're often out of breath capacity. Trained respiratory muscles delay this limiter and allow sustained performance at higher intensities.
The French study he discussed examined trained pro cyclists. Half received structured inspiratory muscle training (30 breaths twice daily at 60–80% of maximum inspiratory pressure) over 48 weeks. The other half didn't. The training group showed 6% FTP gains over the period. The control group showed minimal change.
For a pro cyclist already at the edge of trainable performance, 6% is enormous. For an amateur with more performance headroom, the gains often run higher.
The cycling-specific breathing limiter
The cyclists who benefit most from respiratory training have a specific profile. The diagnostic questions:
Does breathing feel like the limiter on hard efforts? The cyclist who reports "I can't get enough air in" during VO2max work or sustained threshold efforts is describing the respiratory limiter directly.
Do you blow up before your legs do on long climbs? The cyclist whose legs feel fine but whose breathing fragments at minute 8 of a 12-minute climb has respiratory fatigue.
Do you snore or breathe through your mouth at night? Indicators of poor nasal breathing patterns and likely diaphragmatic dysfunction.
Do you carry tension in the upper chest and shoulders? Often a sign of shallow chest breathing rather than diaphragmatic breathing.
Does sustained effort feel like running out of oxygen rather than burning legs? The oxygen-availability subjective experience versus the muscle-fatigue subjective experience.
Cyclists answering yes to two or three of these are likely respiratory-limited to some extent. The training intervention is high-leverage.
Cyclists who answer no to most — who feel the leg burn before any breathing constraint — may not benefit as much from respiratory training. The limiter is elsewhere.
The inspiratory muscle training protocol
The Sellars-cited French study used a specific protocol that's been replicated in subsequent research.
Device. A resistive breathing trainer — POWERbreathe, Airofit, Breather, or equivalent. These create resistance on inhalation, forcing the diaphragm and intercostal muscles to work harder per breath. Cost ranges from $100 (basic Breather) to $300 (Airofit Pro with smartphone app).
Intensity. 60–80% of maximum inspiratory pressure (MIP). Most devices have settings to calibrate this. Start at 50% for the first week to learn the technique, then progress to 60–80%.
Volume. 30 breaths per session, twice daily. Morning and evening. Each session takes about 5–10 minutes including the breath count and brief rest between sets.
Technique. Slow controlled inhalation against the resistance, then unforced exhalation. The focus is on full diaphragmatic expansion — chest stays relatively still, belly expands forward and to the sides. Many cyclists with shallow chest-breathing habits find this awkward initially and need 2–3 weeks to develop the pattern.
Progression. Increase resistance every 2–3 weeks as the breathing strength develops. The MIP measurement should rise across blocks; the device usually tracks this.
Adaptation timeline. Initial neuromuscular learning 2–3 weeks. Strength gains 6–12 weeks. Full adaptation for FTP effect 6–12 months for elite athletes. Amateur cyclists often see initial FTP transfer earlier (3–6 months) because the baseline respiratory function is further from maximum.
Nasal breathing during cycling
Below threshold intensity, nasal-only breathing is achievable and beneficial. The mechanism is CO2 tolerance development. Nasal breathing produces slightly slower exhalation, which raises end-tidal CO2 levels. The body adapts to higher CO2 tolerance, which translates to better performance at high intensity (where CO2 buildup is the limiter).
Easy rides. Nasal-only breathing for the entire ride. Initially feels harder than mouth breathing because the airflow is restricted. Within 2–3 weeks the discomfort fades and the body adapts.
Moderate intensity. Nasal-only often becomes uncomfortable. Some cyclists can sustain it; most need to add mouth breathing above 75% of FTP.
Hard efforts. Mouth breathing is necessary above threshold. The respiratory demand exceeds what nasal breathing can supply. Forcing nasal-only at this intensity reduces performance.
Recovery rides. Nasal-only with intentional focus on slow controlled breathing. Activates the parasympathetic system and accelerates recovery.
The cumulative effect of nasal breathing on easy rides — daily, across months — is improved CO2 tolerance that transfers to hard sessions. The cyclist who develops this habit consistently produces more sustained power at high intensity.
Mouth taping for sleep
The controversial practical application. The evidence supports it for most adults without serious breathing pathology. The mechanism is forcing nasal breathing during sleep, which improves sleep quality, CO2 tolerance, and morning resting heart rate.
Why it matters for cyclists. Sleep quality is the master recovery tool. The cyclist who mouth-breathes during sleep — and most adults do at least part of the night — gets lower-quality recovery regardless of total sleep duration. Nasal-breathing sleepers wake fresher, recover faster between training sessions, and report better next-day performance.
The protocol. Start with a small piece of medical tape (3M Micropore is the standard recommendation) placed horizontally across the closed lips, sealing them gently. Some cyclists prefer vertical strips at the corners of the mouth, which allows some mouth opening if needed.
The progression. First few nights: tape may come off. The body resists the new pattern. Within 1–2 weeks most adults adapt and sleep with the tape intact.
The cautions. Anyone with sleep apnoea should not mouth-tape without medical guidance. Anyone with severe nasal congestion (allergies, deviated septum) needs to address the underlying issue first. Anyone uncertain about their breathing should consult a doctor before starting.
Alternative. Nasal strips can improve nasal airflow without taping the mouth. Useful for cyclists who feel the mouth-tape concept too intrusive but want the benefits of better nasal breathing.
Diaphragmatic breathing as recovery
The third application of breathing for cyclists is recovery-focused. Slow controlled diaphragmatic breathing activates the parasympathetic nervous system, which is the recovery branch of the autonomic system.
The protocol. 5–10 minutes of slow diaphragmatic breathing immediately after hard sessions. Inhale through the nose for 4 counts, exhale through the nose for 6–8 counts. Focus on belly expansion rather than chest expansion. Sometimes called "box breathing" or "4-7-8 breathing" in different traditions.
The mechanism. Slow exhalations trigger the vagus nerve and activate parasympathetic dominance. Heart rate drops. Blood pressure lowers. The body shifts from sympathetic (fight-or-flight) to parasympathetic (rest-and-digest) state. Recovery begins faster.
When it helps. After hard interval sessions. Before sleep. During recovery weeks. As a stress management tool during high-stress life periods.
When it doesn't help. Before hard sessions (you want sympathetic activation for performance). Immediately before competition (same reason).
The cumulative effect of consistent diaphragmatic breathing practice is improved autonomic balance and faster recovery between sessions. Many cyclists who add this protocol notice morning HRV improvements within 4–6 weeks.
CO2 tolerance training
The advanced layer for cyclists who want to push respiratory training further. CO2 tolerance is the body's ability to function at high CO2 levels — a limiter for sustained high-intensity exercise.
Breath-up drills. A series of slow inhales followed by progressively longer breath holds. Standard protocol: inhale for 4, hold for as long as comfortable, exhale for 6, repeat. Build the hold duration across weeks.
Triangle breathing. Inhale 4, hold 4, exhale 4, repeat. Equal phases build the basic CO2 tolerance.
4-7-8 breathing. Inhale 4, hold 7, exhale 8. Asymmetric structure with longer hold and exhalation. Higher CO2 stimulus.
On-bike CO2 tolerance. Nasal-only breathing on easy rides forces some CO2 elevation naturally. The compound effect of this practice across months is meaningful CO2 tolerance development.
The detail and the specific protocols are in the breathing techniques cycling performance guide.
What this looks like in a week
A cyclist running the full respiratory training protocol:
Daily. 10 minutes inspiratory muscle training (5 minutes morning, 5 minutes evening). Nasal-only breathing during all easy rides. Mouth taping during sleep.
Post-hard-session. 5–10 minutes diaphragmatic breathing as recovery activation.
Weekly. One dedicated CO2 tolerance session — 10 minutes of structured breath-up drills.
Monthly. Maximum inspiratory pressure measurement to track respiratory strength progression.
Total time investment: about 90 minutes per week. The training is mostly stackable with other activities (driving, working, watching TV) rather than requiring dedicated time slots.
Common mistakes
Expecting fast results. The full FTP benefit takes 3–12 months. Cyclists who try the protocol for 2 weeks and give up don't see the meaningful adaptations.
Forcing nasal breathing too high. Nasal breathing at threshold or above performs worse than mouth breathing. Don't try to be a nasal breathing purist above moderate intensity.
Mouth taping with breathing pathology. Sleep apnoea, severe congestion, or other breathing problems need addressed first. Mouth taping with these issues can be dangerous.
Skipping the warm-up adaptation. First few sessions with the respiratory trainer should be at lower intensity to learn the technique. Going straight to 80% MIP usually produces lightheadedness or hyperventilation.
Treating it as optional. Cyclists who do the protocol when they remember don't see the benefit. The daily consistency is what produces the adaptation.
What to do next
Start with the Plateau Diagnostic — four minutes, free, returns the one change most likely to move your numbers. If breathing is your hidden limiter, the audit surfaces it — most amateurs don't think to test for it. If breathing feels like your limiter — you blow up before your legs give out, you feel oxygen-restricted rather than leg-burned — buy a respiratory muscle trainer and start the protocol. POWERbreathe and Airofit are the most common options. The investment is around $200 and the time commitment is 10 minutes daily.
If you snore, mouth-breathe during sleep, or wake feeling unrefreshed despite adequate sleep duration, try mouth taping for 2 weeks. Start with surgical tape at the corners of the mouth, not a full seal. The morning HRV usually improves within 1–2 weeks if nasal breathing was the issue.
For specific protocols, the Not Done Yet community at $195/month runs occasional focused sessions on breathing and recovery. For full one-on-one programming including respiratory work integration, the Roadman Method at $297-397/month is the structured 12-month route. The work covered in the Team Visma breathing sensor research is also worth reading for cyclists interested in the latest respiratory monitoring research.
Breathing is the underrated training variable. Most amateur cyclists have substantial respiratory headroom that no amount of interval work will access. The training is cheap, the time investment is small, and the gains compound across months. Worth testing.