In endurance training, Rating of Perceived Exertion (RPE) has long been a trusted compass—an intuitive guide to how hard an athlete feels they’re working. But how reliable is this perception in real-time, especially under fatigue, heat, or glycogen depletion? More importantly, can we measure how well athletes are controlling their RPE, and should we compare what they report to what their body is actually saying?
This is where respiratory frequency (fR)—the number of breaths per minute—steps into the spotlight as a powerful, often overlooked physiological metric. Recent research shows a strong, consistent correlation between fR and RPE across various exercise protocols, from continuous to interval training. In fact, fR may be a better marker of actual physical effort than heart rate, VO₂, or even blood lactate in many contexts.
Why? Because fR is directly modulated by central motor command—the same neural drive that governs perceived exertion. This means that when an athlete breathes faster, it reflects not just metabolic load but also the neural sense of effort they are experiencing. And unlike HR or VO₂, fR responds nearly instantaneously to changes in workload, especially during high-intensity intervals.
The Importance of Comparing Expected vs. Reported RPE
Coaches often prescribe training zones based on expected effort levels. When an athlete reports RPE significantly higher or lower than expected, it could indicate under-recovery, illness, or motivational issues—or simply a mismatch between physical and perceived strain.
Here’s where fR becomes a valuable validator. For instance, if an athlete reports RPE = 13 (“somewhat hard”) but their fR is at 88% of their fRmax (which typically correlates with RPE ~17), you now have an objective reason to question the subjective report.
By continuously measuring fR with CHASKi, coaches can monitor in-session effort in real time—and correlate it with RPE post-session to track how well athletes are tuning into their bodies.
Applications for Training Monitoring
- Session Quality Control: Use discrepancies between fR and RPE to identify when athletes are mentally off or physiologically overreaching.
- Fatigue Detection: Because fR is sensitive to muscle damage, glycogen depletion, and heat stress, unexpected rises in fR for a given RPE can flag red zones.
- Objective Feedback Loop: By mapping normalized fR to RPE scales (e.g., 80% fRmax ≈ RPE 15), you can build a robust, real-time feedback system—especially valuable for self-coached athletes.
Bottom Line
Controlling RPE is critical—not just feeling the effort but regulating it to match training goals. Comparing expected RPE with both reported RPE and objective fR gives coaches a sharper lens on training quality and athlete status. As wearables evolve, expect fR to play a starring role in precision endurance training.
Ready to Take RPE Monitoring to the Next Level?
With CHASKi, you don’t have to rely on guesswork. Our wearable tracks Respiratory Frequency in real time, giving you objective insight into how hard your athletes are truly working—second by second. Whether you’re coaching a squad or optimizing your own training, CHASKi helps you compare expected vs. actual RPE with precision.
See how fR can revolutionize your training monitoring—try CHASKi today.
Sources
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[3] Marcora, S. M. (2009). Perception of effort during exercise is independent of afferent feedback from skeletal muscles, heart, and lungs. Journal of Applied Physiology, 106(6), 2060–2062. https://doi.org/10.1152/japplphysiol.90378.2008
[4] Nicolò, A., Bazzucchi, I., Haxhi, J., Felici, F., & Sacchetti, M. (2014). Comparing continuous and intermittent exercise: an “isoeffort” and “isotime” approach. PloS one, 9(4), e94990. https://doi.org/10.1371/journal.pone.0094990
[5] Nicolò, A., Marcora, S. M., & Sacchetti, M. (2016). Respiratory frequency is strongly associated with perceived exertion during time trials of different duration. Journal of Sports Sciences, 34(13), 1199–1206. https://doi.org/10.1080/02640414.2015.1102315
[6] Nicolò, A., Massaroni, C., & Passfield, L. (2017). Respiratory frequency during exercise: The neglected physiological measure. Frontiers in Physiology, 8, 922. https://doi.org/10.3389/fphys.2017.00922
[7] Robertson, R. J., Falkel, J. E., Drash, A. L., Swank, A. M., Metz, K. F., Spungen, S. A., & Allison, T. G. (1986). Effect of blood pH on peripheral and central signals of perceived exertion. Medicine and Science in Sports and Exercise, 18(2), 114–122. https://doi.org/10.1249/00005768-198602000-00019