RPE: The Most Underrated Metric in Endurance Training

With all the new tech and data available—power meters, heart rate monitors, and advanced analytics—it’s easy to overlook one of the simplest yet most valuable training tools: Rate of Perceived Exertion (RPE). While heart rate and power have their place, RPE remains the most adaptable and insightful metric for endurance training. I always start by assessing effort first, then use other data—like HR, pace, or power—as secondary validation. And I’m not alone. Research consistently shows that RPE is not just a backup metric; in many cases, it outperforms other data points when it comes to effective training and race execution.

The Science Behind RPE

RPE is a perceptual measure of effort, typically rated on a 6–20 or 1–10 scale, depending on the system used. The most well-known version, the Borg Scale, was developed in the 1970s to correlate with heart rate (Borg, 1982). More recent research shows that RPE can be as reliable as HR and power for prescribing and monitoring training intensity (Faulkner et al., 2022; Roos et al., 2020).

Studies indicate that endurance athletes who develop strong pacing skills using RPE are better able to manage effort fluctuations and sustain performance in variable conditions (Smits et al., 2019). This is particularly useful in triathlon, where terrain, temperature, and fatigue all impact performance.

Why I Prioritize RPE Over HR and Power

1. Heart Rate is Inconsistent

HR is a useful physiological marker, but it’s highly variable. External factors like heat, dehydration, caffeine, and stress can influence HR, making it unreliable for real-time decision-making (Laursen & Buchheit, 2019). It also lags behind effort changes, meaning it’s not ideal for pacing short intervals (Maunder et al., 2018).

2. Power is Objective but Doesn’t Reflect Internal Effort

Power meters measure work output in watts, providing real-time data on effort. While this is valuable, it doesn’t account for how an athlete feels. Holding a prescribed wattage can sometimes lead to overexertion, especially when fatigue sets in. Studies show that experienced endurance athletes often regulate effort more effectively using RPE than power alone (Foster et al., 2017).

3. RPE Adapts to Daily Variability

Unlike HR and power, RPE adapts to fluctuations in fatigue, stress, and environmental conditions. Research supports the idea that training with RPE helps athletes develop better pacing skills and avoid burnout (Impellizzeri et al., 2019). Because it’s based on internal feedback rather than external numbers, it’s the most flexible and intuitive metric for long-term training success.

RPE and Pace: The Missing Considerations

If workouts are prescribed in pace, they need to include a range rather than a fixed number, along with considerations for external factors. Pace can be affected by:

• Surface type: Running on trails versus pavement will significantly impact pace.

• Elevation changes: Hills naturally slow you down going up and speed you up going down.

• Temperature and humidity: Heat and humidity can make a usual pace feel much harder.

• Wind: A headwind makes maintaining a given pace much more challenging, while a tailwind makes it easier.

Relying only on pace without considering these variables can lead to overexertion or underperformance. Instead, using RPE allows for real-time adjustments based on how effort truly feels, making training more effective.

Tuning Into Your Body: The Race-Day Advantage

One of the biggest benefits of training with RPE is that it teaches athletes to tune into their bodies—a skill that becomes invaluable on race day. If an athlete relies too heavily on external data like power or HR, they may struggle when conditions change or when their devices fail. By developing an intrinsic sense of effort, athletes can make real-time adjustments based on how they feel, rather than being tied to rigid numbers.

A real-world example of this is during a bike workout, where athletes often ask: “What wattage should I hold?” While power targets are useful, an athlete who knows what their threshold effort feels like can adjust more effectively to wind, hills, or fatigue. I can predict an approximate range of power I can push at a specified effort. Some days I’m on the upper end of that power and it feels great; other times, to get to that same number, I really have to dig. Relying on the feel of a threshold workout helps me execute it at the right intensity, ensuring I don't push too hard or hold back too much.

How to Integrate HR, Power, and RPE

Rather than relying solely on one metric, the best approach is to use RPE as the foundation and HR or power as validation tools:

• Start with RPE – Learn to recognize how different intensities feel. For example, a Zone 2 endurance effort should feel like an RPE of 4–5, while a threshold effort should feel like an 8 (Seiler & Kjerland, 2006).
  

• Use HR and power as secondary metrics – Check HR and power after the session to ensure your effort matches the intended training zone.
  

• Adjust for fatigue and conditions – On days when HR is high due to heat or stress, or power is lower due to fatigue, using RPE ensures you don’t push too hard or back off unnecessarily.

Conclusion: Effort First, Metrics Second

Training smart isn’t about fixating on numbers—it’s about learning to trust your effort. HR and power provide useful insights, but RPE remains the most adaptable, reliable tool for endurance athletes. Developing a strong sense of effort perception will make you a better, more intuitive competitor. Use the numbers, but let effort lead the way—because when it comes down to it, on race day, your body knows best.

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The information provided in this blog post is based on personal experiences and research. It is intended for informational purposes only and should not be taken as medical, legal, or professional advice. Athletes should consult with their healthcare provider or a qualified coach before making significant training or health-related decisions.