Most cyclists spend thousands on lighter wheels, better tyres, and aerodynamic kit. They rebuild their FTP zones after every test block and argue about training load metrics in online forums. Very few spend ten minutes a day training the muscles that move air in and out of their lungs. That is a gap worth closing.
The research is not ambiguous. Structured inspiratory muscle training has produced FTP improvements of up to 6% in trained cyclists across multiple studies. Six per cent on a 300-watt FTP is 18 watts — more than most riders gain from a full training block. The cost is a £30 device and two sets of 30 breaths per day.
Episode 28 of the Roadman Cycling Podcast covers this in detail. Dr. Sellers walked through the physiology, the protocols, and the practical application for riders at every level. What follows is the framework from that conversation, built out with the research behind it.
Why breathing limits cycling performance
The respiratory system is rarely the first thing a coach looks at when a rider hits a ceiling. That instinct is understandable — legs produce power, so legs get the attention. But the lungs and the muscles that drive them are part of the same closed system. When one part gets stressed, the whole system responds.
At intensities above roughly 75% of VO2max, ventilation rates climb steeply. A trained cyclist at threshold is moving somewhere between 80 and 120 litres of air per minute. The diaphragm, intercostals, and accessory respiratory muscles are working hard to do that, and they are competing for the same cardiac output that your legs need.
This is not a fringe theory. The metaboreflex — a cardiovascular reflex triggered by fatigued respiratory muscles — causes the body to vasoconstrict blood flow to the legs in order to protect the diaphragm. Less blood to the legs means less oxygen delivery, which means lower sustainable power. The chain from "tired breathing muscles" to "slower rider" is direct and measurable.
The practical implication is straightforward: strengthen the respiratory muscles and you reduce the threshold at which that reflex fires. You protect leg blood flow for longer, and you sustain higher power outputs before the system starts making trade-offs you don't want it to make.
The respiratory muscle fatigue effect
Dr. Sellers was specific about when this effect becomes relevant. It is not a factor during a 20-minute Zone 2 ride. It becomes significant at threshold and above — the exact intensities that determine race performance and FTP test outcomes.
Research using inspiratory muscle fatigue protocols shows that pre-fatiguing the respiratory muscles before a time trial reduces performance by 3–5% in trained cyclists. Conversely, inspiratory muscle training that strengthens those same muscles has produced time trial improvements of roughly the same magnitude — sometimes more.
The diaphragm behaves like any other skeletal muscle. Train it with progressive overload and it adapts. Neglect it and it becomes the weakest link in the chain at high intensity. Most riders have done years of hard cycling that has improved cardiac output, lactate processing, and leg strength, but have done nothing specific for the respiratory muscles. That imbalance is the opportunity.
There is also a secondary effect worth noting: reduced perception of breathlessness. Stronger respiratory muscles mean less effort required to move a given volume of air. At the same absolute intensity, the subjective sensation of breathing hard is lower. That matters in long efforts and in racing situations where pacing decisions are influenced by how hard you feel you are working.
For triathletes specifically, this is compounded. A hard bike leg creates respiratory muscle fatigue that carries into the run. If you want to protect your run — which is the central principle of how we approach coaching the bike-run combination — keeping respiratory muscles fresh is part of that equation.
Inspiratory muscle training devices
The two devices that appear most consistently in published research are the POWERbreathe Medic and the Ultrabreathe. Both use an adjustable spring mechanism that creates resistance on the inhale. The exhale is unloaded. You breathe in hard against resistance, breathe out freely, repeat.
The POWERbreathe K-series devices have an electronic feedback component that tracks your peak inspiratory flow rate and training load over time. They are more expensive — around £200–£400 depending on the model — but the feedback is useful for ensuring you are training at the right intensity. The basic spring-loaded models at £25–£40 work equally well if you are disciplined about your resistance setting.
Start at 30–40% of your maximal inspiratory pressure (MIP). To estimate MIP, exhale fully and then inhale as hard and fast as you can through the device against its maximum resistance. The highest setting you can just barely complete a full breath on is roughly your MIP. Set your training resistance at 30–40% of that to begin.
Progress by increasing resistance 5–10% every two weeks. After four weeks you should be working at 50–60% MIP. Beyond that, gains in respiratory muscle strength continue but the crossover to cycling performance appears to plateau in most studies. The dose-response relationship is not linear indefinitely.
One important note: IMT is not breath-holding training and it is not about slowing your breathing down. It is resistance training for the inspiratory muscles, with normal breathing rhythm. Thirty controlled, forceful inhales against resistance, twice per day, is the protocol the research supports.
Breathing patterns during efforts
Separate from IMT, how you breathe during rides matters. Most cyclists develop breathing habits over years of training without ever examining them. Those habits are not always optimal.
At Zone 1 and Zone 2 intensities, nasal breathing is achievable for most riders and carries real benefits. The nose filters air, humidifies it, and slows the breathing rate slightly. Slower, more controlled breathing at low intensities reduces CO2 washout, which improves CO2 tolerance over time. Better CO2 tolerance means the urge to breathe — driven by rising CO2, not falling oxygen — fires at a less intrusive level during hard efforts.
Nasal breathing at high intensity is not realistic or beneficial. Above roughly 70% of VO2max, you need the airflow that mouth breathing provides. Forcing nasal breathing at threshold or above imposes an unnecessary ventilatory restriction. The goal is not to become a nasal breather at all intensities — it is to use nasal breathing strategically during easy work to build the underlying physiology.
Rhythm matters more than most riders realise. During sustained hard efforts, breathing that synchronises loosely with pedal stroke — exhaling on the power phase, inhaling on the recovery — can reduce perceived effort and improve muscular coordination. This is harder to maintain as intensity rises, but at threshold it is achievable with practice. Start by simply noticing your breathing pattern during efforts rather than trying to change it immediately. Awareness comes before control.
Breath-holding or pushing through moments of acute breathlessness during intervals tends to create tension through the neck, shoulders, and upper back. That tension costs energy and limits power transfer. Consciously relaxing the upper body during hard efforts — dropping the shoulders, loosening the grip on the bars — often improves breathing efficiency without any direct breathing intervention.
For riders looking to improve FTP, integrating breathing pattern awareness into threshold intervals is a low-cost addition that pays dividends over time.
The 6% FTP gain study
The 6% figure comes from research examining trained cyclists who added IMT to their existing training. The specific protocol involved 30 breaths at 50% MIP, twice daily, over eight weeks. FTP was tested before and after using a standard 20-minute test. The treatment group improved by an average of 6%. The control group, which continued their normal training without IMT, improved by less than 1%.
It is worth being precise about what "trained cyclists" means in this context. The studies typically involve riders with FTPs in the 3.5–4.5 W/kg range, training 8–12 hours per week. Untrained or novice cyclists have larger headroom for improvement across all systems, so respiratory training may produce smaller relative gains because other limiters are more pressing. Highly trained athletes — above 4.5 W/kg — may see smaller absolute gains but are also closer to their overall physiological ceiling, making 6% a more significant marginal improvement.
The mechanism, as discussed above, is primarily reduced metaboreflex activation during hard efforts. Secondary mechanisms include improved respiratory muscle efficiency (less oxygen consumed by the breathing apparatus itself) and reduced perceived exertion at given power outputs. All three contribute to the FTP outcome.
Prof. Stephen Seiler's work on physiological limiters in endurance athletes reinforces the broader point here. Seiler has argued consistently that endurance performance involves multiple systems working in coordination, and that identifying the weakest link in that chain — rather than applying generic training stimuli across the board — is where meaningful gains come from for already-trained athletes. For a significant proportion of trained cyclists, respiratory muscle strength is that weakest link.
A 4-week breathing protocol
This protocol requires a POWERbreathe or comparable IMT device, 10 minutes per day, and a baseline MIP estimate.
Week 1–2: 30 breaths at 30% MIP, twice daily (morning and evening). Focus on full, forceful inhales against resistance. Normal exhale. Rest 1–2 seconds between breaths. Total time: 3–4 minutes per session.
Week 3–4: Increase resistance to 40–45% MIP. Same volume — 30 breaths, twice daily. If you cannot complete 30 consecutive breaths at the new resistance, drop back one step and build again.
From week 5, progress to 50% MIP and hold there for weeks 5–8. This is the maintenance and consolidation phase. Research shows most of the FTP gains occur between weeks 4 and 8 as the respiratory muscles complete their adaptation cycle.
Alongside the IMT work, add nasal breathing to all Zone 1 and Zone 2 riding for the full four weeks. Do not force it if you are genuinely struggling to meet ventilatory demand — nasal breathing should feel manageable, not restrictive. As a rule, if you cannot hold a conversation while nasal breathing on a ride, the intensity is too high for this practice.
Finally, spend five minutes per week — one focused 5-minute block, not scattered throughout training — deliberately practising a relaxed upper body while breathing hard. Do this during a threshold or Sweetspot interval. Notice tension in the jaw, shoulders, and hands. Release it consciously. This single habit, practised consistently, has a noticeable effect on breathing efficiency during hard efforts within two to four weeks.
If you want this built into a structured, individualised programme — one that accounts for your current FTP, training history, and competition schedule — the Not Done Yet coaching programme brings all of it together: training, nutrition, strength, recovery, and the accountability to actually execute it, for $195/month. The work is specific. The gains are real.