Breathing Frequency: The Overlooked Metric That Could Revolutionize Endurance Training
For decades, endurance athletes and coaches have searched for the perfect way to measure training load and intensity. Heart rate and power have long been the go-to metrics, but both have their limitations. Heart rate can be influenced by factors like sleep and hydration while power measures external load, not the internal stress on the body. Perceived exertion (RPE) is often considered the gold standard but it’s subjective and hard to quantify in real time.
But what if there was a metric that was both quantifiable and closely matched our perception of effort? Enter breathing frequency.
What Is Breathing Frequency?
Breathing frequency is simply the number of breaths you take per minute. Like heart rate it’s easy to measure, especially with the latest wearable technology. But unlike heart rate breathing frequency is directly controlled by the same part of the brain that governs our perception of exertion. In other words, as your effort increases your breathing rate rises in step with how hard you feel you’re working.
Why Is Breathing Frequency So Valuable?
An interview with Dr. Stephen Seiler and colleagues highlights several reasons why breathing frequency may be the best metric for endurance athletes:
Direct Link to Perceived Effort: Research shows that breathing frequency matches perceived exertion (RPE) more closely than heart rate or power, regardless of whether the effort is continuous or intermittent. This makes it a ‘truth teller’ for how hard your body is actually working.
Less Affected by External Factors: While heart rate can drift due to fatigue, dehydration or heat, breathing frequency remains tightly coupled to effort, especially as fatigue sets in.
Predicts Failure Points: When an athlete’s breathing frequency reserve (the difference between resting and max breathing rate) matches their heart rate reserve, they are at their physiological limit and about to fail or drop off the pace. This makes breathing frequency a powerful tool for pacing and monitoring fatigue.
Potential for Better Training Load Metrics: Traditional metrics like Training Stress Score (TSS) are based on external load and don’t always reflect the true cost to the body. Breathing frequency could help create new, more accurate measures of training stress.
Dt Stephen Seiler
How Does It Work in Practice?
With the advent of accurate chest-strap wearables, it’s now possible to measure breathing frequency in real time during training and racing. Early studies and field tests with professional cycling teams show that breathing frequency can provide actionable insights such as:
Identifying when an athlete is approaching their limit even if heart rate or power don’t show it.
Individualizing training and recovery by tracking how breathing frequency responds to different types of workouts.
Potentially replacing invasive lab tests (like lactate threshold) with non-invasive, field-based ventilatory threshold measurements.
Challenges and Considerations
Like any new metric, breathing frequency isn’t without its challenges. Interpreting the data requires individualization - just as with heart rate, each athlete will have their own range and response patterns. There are also technical hurdles in developing reliable, comfortable sensors and integrating the data into training platforms.
Moreover, breathing frequency should not be used in isolation. The best approach is to triangulate: use external load (power), physiological response (heart rate, breathing frequency) and subjective feedback (RPE) together for a complete picture.
The Future of Breathing Frequency in Endurance Sports
As wearable technology matures and more research emerges, breathing frequency is poised to become a mainstream metric for endurance athletes. It offers a unique window into the body’s response to training and could help athletes and coaches better manage stress, optimize adaptation and avoid overtraining.
In the quest for the perfect metric, breathing frequency may not be the only answer - but it’s a powerful new tool that brings us closer to truly understanding and optimizing endurance performance.
Bevan McKinnon / June 2025
LINKS:
Follow Dr Stephen Seiler on X at https://x.com/stephenseiler
More about Dr Stephen Seiler at https://www.uia.no/english/about-uia/employees/stephens/