Most fitness pros focus on strength, endurance, recovery, but overlook the one system that powers them all: your breath.
Respiratory Muscle Training (RMT) is a performance enhancer hiding in plain sight. By targeting and strengthening the muscles used to breathe, primarily the diaphragm and intercostals, RMT increases breathing efficiency, oxygen delivery, and fatigue resistance. It’s the foundation for greater stamina, stronger recovery, and a more resilient nervous system.
RMT has been used in special operations prep, elite athletic training, and even frontline healthcare to increase physical and mental performance. In one clinical study, Special Forces applicants who completed just four weeks of RMT improved their two-mile run time by 4% and saw a 10x increase in selection rate. Other studies have shown measurable improvements in HRV, stress resilience, and sleep quality, even in high-burnout environments.
At Capacity, we treat breath as the entry point to training your entire system, and the Breather Fit is the device we trust to deliver that training. This page dives into the science, studies, and real-world results that prove it.
Studies showed the effectiveness of RMT in improving the overall performance of athletes, particularly when combining inspiratory and expiratory muscle training.
The BREATHER FIT is the first device to offer both types of training in one device.
Active youth who incorporated inspiratory muscle training at high resistance improved their breathing strength, VO2 max, and 6-minute walk distance.
*VO2 Max: The maximum amount of oxygen an individual can use during maximal exercise.
Carrying load on your back, like rucking or backpacking, increases the fatigue of respiratory muscles compared to normal/regular running or walking. Training these muscles with resistance breathing increased the athlete’s distance covered before fatigue while carrying the load by 20%.
When adding RMT to their training, swimmers took 17% more time to tire compared to swimmers using sham* respiratory muscle trainers or none at all.
*Sham Devices: Devices that look similar to the device being tested, but provide no resistance.
Army ranger recruits who used the Breather Fit decreased their 2-mile run time on average by 39 seconds and were more likely to be selected for special forces.
Not only did rowers who trained their respiratory muscles greatly improve the speed of their 5000m row but they also rowed 3.5% farther in a 6-minute all-out test.
After training their inhale musculature, young swimmers greatly improved their times in the 50m, 100m, and 200m distances compared to a control group.
Professional soccer players in Brazil trained their respiratory muscles over 2 weeks. These players significantly increased their sprint times and exercise tolerance in that short period.
In a controlled trial, athletes breathing only through their nose at 75% VO₂ max were able to run ~32% longer before exhaustion when using external nasal dilator strips
Healthy adults wearing nasal strips delayed the switch to mouth breathing, achieving ~15% longer nasal-only breathing time and ~14% higher nasal ventilation at peak exercise.
A double-blind trial of 71 adolescent athletes found that wearing an external nasal strip increased maximal oxygen uptake by about 5% (39.5 vs 37.5 mL/kg/min) compared to a placebo strip.
In a randomized crossover test, 11–15-year-old runners had ~4% higher VO₂ max when using a nasal dilator strip versus a placebo, along with improved nasal breathing and less perceived exertion.
Adolescent runners reported ~5% lower perceived breathing effort during maximal running tests while wearing nasal strips, indicating easier breathing under intense exercise.
University athletes who wore an elevation training mask during 8 weeks of high-intensity interval cycling saw a significantly larger VO₂max increase (~11% vs ~2% in controls) and higher ventilatory thresholds.
In a study where one group wore an elevation mask during 8 weeks of resistance workouts, the mask group saw ~18% greater VO₂max and higher blood lactate at exhaustion, indicating enhanced anaerobic capacity, compared to control.
In a 6-week cycling HIIT program, only the mask-wearing group significantly improved their ventilatory threshold (~14% increase) and power at that threshold (~19% gain), key markers of endurance capacity, beyond the changes seen in the control group.
In a controlled 6-week program, the group training with a simulated-altitude mask achieved a significantly greater VO₂max improvement, ending about 6% higher than the control group’s VO₂max.
Six sessions of breath-hold hypoventilation training in competitive swimmers increased the number of 25 m sprints they could perform before exhaustion by ~35% compared to normal breathing training.
Limiting breathing frequency during swim training (2 breaths per pool length vs. ~7 normally) for 12 sessions led to a ~6% improvement in running economy in novice swimmers, reflecting more efficient oxygen utilization after this respiratory muscle stress protocol.
Trained cyclists who completed 6 weeks of IMT (resistance breathing exercises) significantly improved their 20 km and 40 km time trial performance (finishing ~3.8–4.6% faster) relative to a placebo group, presumably by reducing respiratory fatigue during endurance effort.
In a simulated shooting task, military trainees who used box breathing before firing scored 1.9 points higher (≈19% improvement) on initial shot accuracy than controls.
In a semester-long trial, graduate students practicing daily pranayama had only 33% high test anxiety (vs 67% in controls) and achieved significantly better exam performance than the control group.
A controlled study found that a single 5-minute session of slow alternate-nostril pranayama made participants respond ~8% faster on a demanding 2-back working memory task, with accuracy also improving about 6%.
In a randomized trial, participants practicing Wim Hof Method breathing (with cold exposure) showed a significantly greater decrease in post-stress rumination than those doing slow breathing controls, suggesting improved mental focus and recovery under pressure.
In a controlled trial, participants practicing Wim Hof Method breathing (with cold exposure) had nearly triple the levels of anti-inflammatory IL-10 and significantly lower pro-inflammatory cytokines after a toxin challenge, indicating a heightened recovery response.
A study in moderately trained females found that breathing at a slow 6 breaths-per-minute pace during a 5-minute post-exercise cool-down significantly sped up heart rate recovery compared to both passive rest and active recovery, reflecting quicker parasympathetic activation.
A clinical trial isolating pranayama techniques showed that slow, deep yogic breathing can significantly increase heart rate variability (RMSSD increased ~20–65% during breathing sessions), indicating strong parasympathetic activation and improved recovery state.
After 6 weeks of inspiratory breathing muscle training, athletes who breathed against resistance during recovery cleared blood lactate faster (about 0.66 mmol/L lower lactate over the first 20 minutes post-exercise) than those with normal passive recovery, aiding quicker metabolic recovery.
