When Dr Andrew Sellars sat down on the podcast and described a French study where respiratory muscle training added 6% to FTP in professional cyclists over 48 weeks, the response from the community was split cleanly in two. Half wanted to know which device to buy. The other half said it sounded too good to be true.
The truth, as usual, sits somewhere between the two. Respiratory muscle training is real. The evidence base is substantial — multiple meta-analyses, dozens of randomised controlled trials, data from populations ranging from elite athletes to patients with chronic obstructive pulmonary disease. It is not new science. Alison McConnell at Brunel University published foundational work on IMT in athletes in the early 2000s. What has changed is the availability of affordable, well-designed training devices and a growing recognition that the respiratory system is a trainable limiter, not a fixed constraint.
But not every cyclist will benefit equally. Not every device is supported by the same quality of evidence. And not every protocol works. If you are going to invest 6-10 minutes a day for 8-12 weeks, it is worth knowing what the research actually says before you start.
The Respiratory Metaboreflex — Why This Matters for Cyclists
The reason respiratory muscle training works is not simply "stronger breathing muscles move more air." The mechanism is more interesting than that, and understanding it explains why certain cyclists benefit more than others.
During sustained high-intensity exercise — a 20-minute FTP test, a hard climb, a time trial — your respiratory muscles (primarily the diaphragm and the external intercostals) are working hard to ventilate your lungs. As these muscles fatigue, they accumulate metabolites. That metabolic distress triggers a sympathetic nervous system reflex — the respiratory metaboreflex — that causes vasoconstriction in the blood vessels supplying your locomotor muscles.
In plain terms: when your breathing muscles tire, your body redirects blood flow away from your legs and toward your diaphragm. Your legs, which were receiving the blood and oxygen they needed to sustain power, now receive less. Power drops. Fatigue accelerates. You slow down — not because your legs are done, but because your breathing is stealing their blood supply.
This reflex has been measured in controlled laboratory studies. Dempsey et al. (2006) published a landmark paper in the Journal of Physiology showing that loading the respiratory muscles during exercise reduced leg blood flow by up to 7% and decreased exercise tolerance significantly, while unloading the respiratory muscles (using a ventilator to assist breathing) improved exercise tolerance.
Respiratory muscle training delays the point at which the metaboreflex activates. Stronger respiratory muscles take longer to fatigue, accumulate metabolites more slowly, and therefore allow your legs to retain their blood supply for longer during sustained efforts.
This is not a theoretical abstraction. It is measurable watts maintained at the sharp end of a time trial.
The Evidence Base — What the Meta-Analyses Show
The strongest summary of IMT research in athletes comes from HajGhanbari et al. (2013), a systematic review and meta-analysis published in the Journal of Sports Sciences, which pooled data from 21 studies (46 outcomes) across various endurance sports.
Key findings:
-
Time trial performance improved by 3.5% in trained athletes following IMT protocols of 4-12 weeks. For context, a 3.5% improvement in a 40km time trial for a cyclist averaging 300 watts is roughly 10 watts sustained — a meaningful gain from an intervention that requires less than 10 minutes per day.
-
Perceived exertion decreased — athletes reported lower ratings of breathlessness and respiratory effort at the same absolute workload after IMT. This matters because perceived exertion drives pacing decisions. If breathing feels easier at 280 watts, you are more likely to sustain 280 watts.
-
Maximal inspiratory pressure (MIP) increased by 18-30% across studies, indicating genuine strength adaptation in the respiratory muscles.
-
The largest benefits were seen in less-trained athletes and those with lower baseline MIP values. Elite athletes with already-strong respiratory muscles showed smaller, sometimes non-significant improvements. This is consistent with the general principle that training adaptations are largest in those furthest from their ceiling.
A 2016 Cochrane review took a more conservative position, noting that study quality was variable, sample sizes were small, and blinding was difficult with resistive breathing devices (subjects know whether they are breathing against real resistance). The review concluded that IMT "may improve endurance exercise performance" but that the evidence was not conclusive at the highest level of certainty.
The fair reading: IMT works for most cyclists, the effects are moderate but meaningful (comparable to other legal marginal gains), and the largest benefits accrue to cyclists who are currently limited by breathing rather than by leg strength or cardiovascular capacity.
The Devices — What Is Available
Respiratory muscle training devices fall into two main categories, and the distinction matters for both evidence and practical use.
Pressure-Threshold Devices
These use a spring-loaded or electronically controlled valve that requires you to generate a specific inspiratory pressure before the valve opens and allows air to flow. The resistance is consistent — it does not change with flow rate, breathing speed, or technique. You either generate enough pressure to open the valve, or you do not.
POWERbreathe Plus (mechanical, circa $40-60): The entry-level pressure-threshold device. Adjustable resistance via a calibrated dial. No electronics, no app, no data tracking. It works. The original McConnell research at Brunel University was conducted with this type of device. If budget is a concern and you just want something evidence-supported, this is the place to start.
POWERbreathe K-Series (electronic, circa $350-500): The advanced version. Electronic resistance control, rep-by-rep data on inspiratory pressure, volume, and power. Connects to an app for tracking progress. Used in several research studies and by some World Tour teams. The data it provides allows precise load prescription (e.g., "set resistance at 60% of your measured MIP").
Threshold IMT (Philips Respironics, circa $20-30): A simple mechanical pressure-threshold device originally designed for respiratory rehabilitation. Cheaper than the POWERbreathe, widely available in medical supply stores, and perfectly functional for the standard 30-breath protocol. Less cycling-specific branding but identical operating principle.
Flow-Resistance Devices
These create resistance by restricting airflow through an orifice of variable diameter. The resistance varies with how fast and how hard you breathe — breathe slowly and the resistance feels lower; breathe explosively and it feels higher. This makes precise load prescription more difficult.
Airofit Pro 2.0 (circa $300-350): The most visible flow-resistance device in the cycling market. Offers both inspiratory and expiratory training modes, app-guided sessions of varying duration and focus (strength, vital capacity, anaerobic threshold), and detailed data tracking. The app experience is polished and the guided sessions reduce decision fatigue. However, the cycling-specific peer-reviewed evidence for this device is limited compared to pressure-threshold devices. Most Airofit-cited research uses general respiratory function outcomes rather than cycling performance measures.
Breather Fit (circa $50-70): A dual-valve device offering independent inspiratory and expiratory resistance dials. Simple, no electronics, no app. Primarily used in speech therapy and respiratory rehabilitation but usable for athletic IMT.
Which to Choose
If evidence purity is your priority, a pressure-threshold device is the more defensible choice. The research base is deeper, the resistance is more precisely controlled, and the protocols used in positive studies are directly replicable.
If user experience, guided training, and data tracking matter more to you, the Airofit Pro 2.0 is a well-designed product that will likely produce similar adaptations — the underlying principle (progressive overload of the respiratory muscles) is the same.
What matters most is that you use the device consistently, with appropriate resistance, following a protocol that resembles what the research tested. The best device is the one you will actually use twice a day for 8 weeks.
The Protocol — What the Research Tested
The majority of positive studies used a remarkably consistent protocol:
30 breaths, twice daily, at 50-70% of maximal inspiratory pressure (MIP), for 6-12 weeks.
That is it. No elaborate periodisation. No complex session structure. Thirty maximal inspiratory efforts against a set resistance, morning and evening. Each session takes 3-5 minutes.
To set the resistance correctly, you need to know your MIP — the maximum pressure you can generate during a single maximal inspiratory effort from residual volume (after a full exhalation). Electronic devices (POWERbreathe K-Series) measure this automatically. With mechanical devices, the common approach is to find the resistance level at which you can complete 30 breaths with the last 5 feeling difficult but achievable. If you cannot finish 30, the resistance is too high. If 30 feels comfortable, it is too low.
Weeks 1-2: Start at 50% of perceived maximum. Focus on technique — sitting upright, full exhalation before each inhalation, maximal effort through the full range of the breath. Two sessions per day, 30 breaths per session.
Weeks 3-6: Increase resistance by one increment every 5-7 days, provided you can complete 30 breaths at the current level. Target 60-70% of MIP by week 6.
Weeks 7-12: Maintain the resistance level that allows you to complete 30 breaths with the final 5-8 being a genuine effort. If adaptation has plateaued, increase by one further increment.
Maintenance (ongoing): After the initial 12-week adaptation block, once-daily sessions at the established resistance level are sufficient to maintain gains. Dropping to zero sessions results in detraining of the respiratory muscles within 4-8 weeks, similar to detraining of skeletal muscle.
Who Benefits Most
Not every cyclist will experience the same return from IMT. The research and clinical experience suggest the following groups benefit disproportionately:
Cyclists who describe breathlessness as their primary limiter. If your typical experience during hard efforts is "my legs feel fine but I cannot get enough air in," your respiratory muscles are likely fatiguing before your locomotor muscles. IMT directly addresses this.
Masters cyclists. Respiratory muscle strength declines by approximately 1-2% per year after age 50, independent of cardiovascular fitness. A 55-year-old cyclist with strong legs and a well-trained heart may be limited by weakening respiratory muscles that have been quietly declining for a decade. IMT can reverse much of this age-related decline.
Heavier cyclists. A 90kg cyclist at the same relative power output (e.g., 3.5 W/kg) produces an absolute power of 315W, requiring significantly higher ventilation than a 70kg cyclist at 3.5 W/kg (245W). The ventilatory demand scales with absolute work rate, and heavier cyclists' respiratory muscles are working harder in absolute terms.
Cyclists returning from respiratory illness. Post-COVID, post-pneumonia, post-bronchitis — any illness that involved the lungs can leave the respiratory muscles deconditioned. IMT is used in clinical rehabilitation for precisely this reason, and the transition to athletic populations is logical.
Time trialists and those who sustain high power for extended periods. The respiratory metaboreflex is most relevant during sustained efforts above 80% of VO2max lasting 10+ minutes. If your racing involves long time trials, sustained climbs, or breakaway efforts, the metaboreflex has more time to affect you.
Cyclists who may benefit less: Those who are already highly trained with no subjective sense of respiratory limitation, and those whose primary limiter is clearly cardiovascular (low VO2max) or muscular (low FTP relative to VO2max). IMT will not fix a weak engine — it protects an engine that is already strong from being throttled by the breathing system.
Integration With Cycling Training
The most common mistake is treating IMT like a warm-up — doing 30 breaths on the PowerBreathe and then jumping straight on the turbo for intervals. This is backwards. Pre-fatiguing your respiratory muscles before a session that demands high ventilation makes the session worse, not better.
Separate IMT from hard cycling sessions by at least 2 hours. The simplest schedule:
- Morning: IMT session (30 breaths, 3-5 minutes) before breakfast or during your morning routine
- Evening: IMT session before bed or after dinner
- Cycling: Whenever it fits your schedule, without concern for IMT timing as long as the 2-hour buffer is maintained
On race days, do not perform IMT within 4 hours of the start. You want fully fresh respiratory muscles for competition.
During a taper, maintain IMT at the same resistance and frequency. The respiratory muscles do not need tapering in the same way that locomotor muscles do — the sessions are too short and too localised to generate systemic fatigue.
During illness, stop IMT and restart when you are fully recovered. Respiratory muscle training while your respiratory system is fighting an infection is counterproductive.
What IMT Does Not Do
To set expectations correctly:
IMT does not increase your VO2max. Your VO2max is limited by cardiac output and oxygen-carrying capacity, not by your ability to move air in and out of your lungs. IMT improves the efficiency and endurance of the muscles that ventilate your lungs, but it does not change the amount of oxygen your blood can carry.
IMT does not replace cardiovascular training. It is a supplement — a marginal gain that works best when layered on top of a well-structured cycling programme. A cyclist who trains 2 hours a week and does IMT will not outperform a cyclist who trains 10 hours a week without IMT. The fundamentals still come first.
IMT does not work overnight. The minimum commitment for measurable results is 4-6 weeks of consistent twice-daily use. If you try it for a week, feel no different, and put the device in a drawer, you have not given it a fair trial.
IMT is not the same as breathing technique. Nasal breathing, rhythmic breathing patterns, diaphragmatic breathing during recovery — these are technique interventions that improve how you use your respiratory muscles. IMT improves the strength and endurance of the muscles themselves. Both have value. They address different problems.
The Practical Recommendation
If you are a cyclist over 40 who trains consistently, whose breathing limits you before your legs do during hard efforts, and who is looking for a legal, evidence-supported, low-time-investment way to gain a few per cent — respiratory muscle training is worth trying.
Buy a pressure-threshold device (POWERbreathe Plus at the budget end, K-Series if you want data). Follow the 30-breath, twice-daily protocol at 50-70% of MIP. Commit to 8 weeks minimum. Separate it from your riding. Track whether your subjective breathing during hard efforts improves.
It is not revolutionary. It is not going to transform you from a Cat 4 to a Cat 2. But for the right cyclist, with the right limiter, 6-10 minutes a day for the cost of a few inner tubes, it is one of the best-supported marginal gains available.
Your legs are probably not the problem. Your breathing might be.
Marginal gains only work when you have the fundamentals right. The Roadman community on Skool is where training structure, nutrition, and details like this come together. See what is inside.