Breathing Rate vs. Heart Rate: Which Metric Matters More for Runners?

From resting heart rate to training zones to heart rate variability, heart rate data gets a lot of glory when it comes to running—and for good reason! But now, some athletes are starting to talk about respiratory metrics like breathing rate, blood oxygen, and tidal volume (how deep you breathe).These numbers can reflect the health of your respiratory system, which “can certainly affect performance” for runners, says Markus Amann, PhD, a professor of anesthesiology at the University of Utah whose research focuses on breathing, circulation, and central nervous system fatigue.Now, new wearables, like Tymewear VitalPro, are even hitting the market, focusing on respiratory numbers, claiming to estimate ventilatory thresholds and using those estimates to prescribe training intensity more accurately than via heart rate data alone.But these metrics (and the wearables) are probably not as actionable or meaningful as heart rate data—especially for nonelite runners. “More often, performance is limited by the cardiovascular system and the muscles' ability to sustain high-intensity exercise,” says Jordan A. Guenette, PhD, associate director of the Centre for Heart Lung Innovation at The University of British Columbia.Still, it makes sense to stay aware of how your respiratory system is working and how it factors into your overall running performance. It’s also important to know when you should focus more on your breathing to increase efficiency and improve performance.How the Respiratory System Affects PerformanceFirst, it helps to understand what’s going on physiologically when it comes to the respiratory system during running. When you run, all of your muscles, organs, and tissues are essentially “competing” for cardiac output—the amount of blood that your heart pumps out per minute, says Amann.In elite athletes, cardiac output can be more than 30 liters a minute while in the average runner, it’s closer to 15 or 20, Amann adds. “The biggest hog when running is of course the legs—they need the most blood,” he says, but the brain, heart, and respiratory system want a “piece of that pie,” too.Your body has protective mechanisms in place so that, once you reach a certain intensity, which is around 80 percent of VO₂ max, the respiratory muscles “steal” the blood from the legs. “The performance limitation comes in because at these high intensities, there is a constriction (called vasoconstriction) that kicks in and limits the amount of blood that flows to the legs in favor of the respiratory muscles,” Amann explains. “When you are a very highly trained athlete, the pulmonary system often has not kept up with adaptation with training so the legs basically outrun the lungs.”While this can happen to less experienced runners, too, Amann points out that this only happens at high intensities (above 85 percent of VO₂ max) and he wouldn’t consider it a major limiting factor in beginners.When the legs outlast the lungs, this can cause a feeling of being out of breath, even when your muscles don’t feel like the limiting factor. “As runners become fitter, their heart rate at a given pace typically decreases because the cardiovascular system becomes more efficient at delivering oxygen to the muscles and using that oxygen to produce energy,” Guenette says. “However, when exercise intensity increases, ventilation still has to rise substantially because the muscles are producing more carbon dioxide and other metabolic byproducts that need to be managed [by the respiratory system].”Breathing does become more efficient as runners get more aerobically fit (you’ll have a lower breathing rate for the same pace), but not because of increasing lung size or airway dimensions (changes similar to cardio system), but simply because your body gets better at using oxygen and handling the metabolic demands of running, Guenette explains.How Breathing Should Feel During a Run Guenette breaks down how breathing should feel during different types of runs. Most runners do not need to consciously control their breathing, he says. “The respiratory system automatically adjusts breathing frequency, depth, and whether we breathe through the nose, mouth, or both to match the demands of exercise, and in healthy runners, this regulation is extremely effective.”That said, becoming more aware of breathing can still be useful. “It can help runners stay relaxed, avoid starting hard efforts too aggressively, and develop a better sense of effort,” he says. “The goal is not to force a particular breathing pattern, but to use breathing as one of several signals that help gauge exercise intensity and effort.”Easy runs: Breathing should feel relaxed and controlled. “You should be able to speak in full sentences without much effort,” he says. “Ventilation is relatively low and the sensation of breathing is comfortable.” For easy runs, some runners find nasal breathing comfortable, and it can be a useful way to keep intensity controlled, he adds.Tempo runs: Breathing becomes more noticeable but still manageable. “Most runners can talk in short phrases, but not full sentences,” he says. “You are breathing deeper and faster because your body is producing more carbon dioxide, and your ventilatory drive increases to clear it. The sensation should feel steady and sustainable.”At this point, trying to deliberately slow or control breathing usually does not improve performance and may make the effort feel more difficult, Guenette says. “A better approach is to let breathing respond naturally while using pace, perceived effort, or heart rate to guide intensity,” he explains.VO₂ max intervals: Breathing becomes very intense and the sensation of breathlessness increases substantially. “That is normal for work done near the top end of your aerobic capacity,” Guenette points out. “Talking becomes nearly impossible and ventilation rises sharply because the metabolic demand is so high.”But even if you do start to breathe really heavily, it's not necessarily a bad thing. “The sensation of breathlessness reflects the body's increasing need for ventilation and the perception of the work required to breathe,” Guenette says. “Multiple factors contribute, including the amount of air being moved, the effort of the breathing muscles, sensory feedback from the respiratory system, and the brain’s drive to increase ventilation.”Factors That Influence Breathing When RunningMany factors influence how hard it feels to breathe while running, Guenette says, including:Allergies or nasal congestion can make airflow feel restricted, which can increase the sense of breathing discomfort. Poor air quality can irritate the airways and make breathing feel more noticeable for any given pace. Hot conditions can force the cardiovascular and respiratory systems to work harder to help the body cope with the increased thermal stress, which can make breathing feel more difficult. High humidity can add to that sensation by making exercise feel even more uncomfortable. Altitude reduces the amount of oxygen available with each breath, so breathing rate rises at intensities that would normally feel easy at sea level. Anxiety or stress can elevate breathing rate and make breathing feel less controlled.Running mechanics could potentially play a role too. Thoracic mobility and posture influence how freely the chest and torso can expand, but this is an area where the evidence is still fairly limited. Signs Something May Be OffWhile there is a lot of individual variability in how runners perceive breathing, and some runners may be more attuned to breathing sensations than others, here are a few signs that something might be off and it would be worth talking to a healthcare provider, per Guenette:Unusually high breathing effort during easy runsDifficulty controlling breathing at moderate intensitiesWheezing or chest tightnessA sudden drop in performance accompanied by breathlessnessWhat You Can Do About Your Respiratory MusclesFirst, the bad news: You can’t really increase lung size or volume—that’s largely genetic, Amann says. If you’re curious where you stand, you can get a pulmonary function test at a hospital or clinic that can tell whether you have limitations (that could point to conditions like emphysema or COPD, as well as things like being a smoker) that may limit performance, as well as whether your lung size and capacity are adequate for your age.The most meaningful “improvements” in respiratory numbers would be seen by people who had a condition and then took steps to manage it, Amann says.For anyone, it’s possible that respiratory muscle training with a device such as the PowerBreathe, designed to train your breathing muscles to work more efficiently, could yield performance benefits. This type of device “can improve whole-body exercise performance and reduce breathlessness during exercise,” Guenette says. But the research is mixed. “I think there are as many papers out there that say it has a beneficial effect on performance as there are that say the opposite,” Amann says.The idea is that you train your respiratory muscles to require less energy, thereby avoiding them “stealing” blood flow from the legs at higher intensities. “The diaphragm and other breathing muscles can become stronger and more fatigue-resistant through targeted respiratory muscle training, just like it does with any other skeletal muscle,” Guenette adds.TRY THESE DIAPHRAGM EXERCISESIt’s also possible that running itself could improve pulmonary function, Amann says. A 2026 study in Cureus found that regular swimming and running were positively associated with improved pulmonary function compared with a sedentary lifestyle in healthy young adult males.So, Should You Track Breathing Metrics? While the experts agree that runners shouldn’t try to mess with their body’s innate respiratory function (by, say, trying to change your breathing rate), there are some cases where ventilatory data may be helpful.“If there is one respiratory metric worth paying attention to, it is probably breathing rate, simply because it is the easiest to measure consistently,” Guenette says. “Breathing rate reflects many of the same physiological stresses as heart rate, including changes in exercise intensity, fatigue, heat, dehydration, stress, and illness,” he explains.While for most runners, heart rate remains the more reliable and actionable metric, breathing rate can still offer useful context over time. “If it trends slightly lower at an easy pace, that may reflect improved aerobic fitness,” Guenette says. “If it’s unusually high for a familiar run, it may indicate fatigue, heat, poor sleep, stress, illness, or inadequate recovery.” As with any physiological metric, it’s best interpreted alongside heart rate, pace, and perceived effort rather than on its own.Jonah Rosner, MS, CSCS, a sport scientist, performance coach, and the founder of Marathon Science, has been testing the Tymewear VitalPro chest strap, which purports to measure breathing rate, tidal volume (how deep you breathe), and minute ventilation (the increase in the amount of air that you breathe every minute) in addition to heart rate, for this express purpose.“For me, the biggest benefit is adding real-time breathing data to the pace, heart rate, and perceived-effort information I already use,” he says. “Heart rate can take time to catch up when intensity changes, while pace can be affected by hills, heat, and wind. Seeing breathing rate and minute ventilation gives me another view of how demanding the session actually is without needing to conduct every assessment in a lab.”“For an amateur runner, the value is less about chasing another number and more about learning what easy, moderate, and hard efforts actually feel like,” Rosner adds. “It is not a diagnosis by itself, but it can help a runner adjust earlier instead of waiting until the session falls apart.”The VitalPro also purports to estimate ventilatory thresholds and prescribe training intensity. “For day-to-day intensity control, I find this more practical than repeated lactate testing, which takes more time and is most useful when the sampling and testing protocol are carefully standardized,” Rosner says.Amann says it all comes down to the accuracy of the data (and there are few sound studies on that): “If the measurements are reasonably accurate, there is potential value in the approach,” says Amann. “Ventilatory thresholds are physiologically meaningful markers and, in theory, may provide more individualized training guidance than generic heart-rate formulas.”The challenge, he notes, is confidence in the threshold estimates themselves. “For most recreational runners, I still think heart rate remains the most practical and accessible training tool,” he says.