When it comes to measuring running performance, most athletes still rely on heart‑rate monitors, but a growing number are looking at breathing rate as an alternative metric.
Why heart rate stays the go‑to metric
Heart‑rate data has long been prized because it directly reflects the cardiovascular system’s ability to deliver oxygen to working muscles. Jordan A. Guenette, PhD, associate director of the Centre for Heart Lung Innovation at the University of British Columbia notes that “more often, performance is limited by the cardiovascular system and the muscles’ ability to sustain high‑intensity exercise.” This makes heart rate a reliable indicator for most non‑elite runners.
Heart‑rate monitors also have the advantage of mature algorithms that translate beats per minute into training zones. For many, the simplicity of checking a wrist‑based sensor and adjusting pace accordingly is sufficient for daily training and race preparation.
What breathing rate adds to the picture
Breathing rate, along with related metrics such as tidal volume and minute ventilation, provides insight into the respiratory system’s workload. Markus Amann, PhD, a professor of anesthesiology at the University of Utah, explains that at around 80 % of VO₂ max, the respiratory muscles begin to “steal” blood from the legs, a phenomenon that can limit performance at high intensities.
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In elite athletes, cardiac output can exceed 30 L per minute, while the average runner typically reaches 15–20 L per minute. The legs demand the greatest share of this blood flow, but the brain, heart, and lungs also compete for the supply. When the respiratory system draws more blood, the runner may feel out of breath even though leg fatigue is not yet the limiting factor.
For most recreational runners, this “steal” only occurs above 85 % of VO₂ max, so it rarely becomes a primary concern. Still, tracking breathing rate can flag unusual fatigue, heat stress, or illness.
Understanding how breathing feels at different paces helps runners use the metric wisely. Easy runs should allow full sentences without strain, while tempo runs limit speech to short phrases. Near‑maximal intervals make talking nearly impossible, a normal sign of high ventilatory demand.
Beyond the data, runners should consider environmental and personal factors that affect breathing. Allergies, poor air quality, high temperature, humidity, altitude, and stress can all raise perceived effort. Even posture and thoracic mobility may influence how freely the chest expands, though research on this is still limited.
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Breathing rate is the most accessible respiratory metric, according to Guenette, because it can be measured consistently with many modern wearables. Devices such as the Tymewear VitalPro chest strap claim to estimate ventilatory thresholds and provide real‑time breathing data alongside heart rate and pace.
While the concept sounds promising, the accuracy of respiratory measurements remains a question. Amann cautions that “if the measurements are reasonably accurate, there is potential value in the approach,” but notes that few sound studies have validated the threshold estimates produced by consumer devices.
From a broader perspective, the interest in breathing metrics reflects a shift toward more holistic training data. As wearables become capable of monitoring multiple physiological signals, athletes can cross‑reference heart‑rate trends with breathing patterns to detect early signs of overtraining or illness. This multidimensional view may help runners maintain consistency, especially when external conditions vary.
Improving respiratory efficiency directly is limited; lung size is largely genetic. However, respiratory muscle training devices such as PowerBreathe claim to enhance muscle endurance, potentially reducing the “steal” effect at high intensities. Research on these devices is mixed, with some studies showing benefits and others finding no impact.
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For runners who suspect a respiratory limitation, a pulmonary function test can identify issues like reduced lung capacity or obstruction. In the absence of a medical condition, the most practical approach remains to let the body regulate breathing naturally while using heart rate, pace, and perceived effort as primary guides.
Breathing rate adds nuance.
In summary, heart rate continues to be the most actionable metric for most runners, but breathing rate offers complementary context. A lower breathing rate at a familiar easy pace may signal improved aerobic fitness, while an unusually high rate could indicate fatigue, heat stress, or illness. Combining both signals can help athletes make more informed training decisions without overcomplicating their routine.
