What Is Rate of Perceived Exertion?
Rate of Perceived Exertion (RPE) is a subjective measure of how hard a person feels they are working during physical activity. It quantifies the internal sense of effort — including factors like breathing rate, heart rate, muscle fatigue, and overall discomfort — on a numerical scale. The two most commonly used scales are the Borg Scale (6 to 20) and the Modified Borg Scale (0 to 10).
RPE provides a practical, equipment-free way to monitor exercise intensity. Because it accounts for the individual's overall physiological and psychological state on a given day, it can be more responsive to real-time conditions than fixed heart rate targets.
Why It Matters for Your Exam
RPE is tested on both NASM and ACE exams as a method for monitoring cardiorespiratory and resistance training intensity. You need to know both scales, how they correlate to percentage of maximal heart rate, and when RPE is the preferred monitoring method over heart rate.
Key exam scenarios include clients on beta-blockers or other medications that blunt heart rate response — in these cases, RPE becomes the primary method for gauging intensity because heart rate is no longer a reliable indicator. You should also know that the original Borg Scale (6-20) was designed so that multiplying the rating by 10 roughly approximates heart rate (e.g., RPE 15 corresponds to approximately 150 bpm).
Key Points to Remember
- The Borg Scale ranges from 6 to 20. A rating of 6 means no exertion at all; 20 means maximal effort. It was designed to correlate with heart rate when multiplied by 10.
- The Modified Borg Scale (CR-10) ranges from 0 to 10. It is simpler and often preferred in practical training settings. Zero is rest; 10 is maximal effort.
- RPE is essential when heart rate monitoring is unreliable, such as with clients taking beta-blockers, those with atrial fibrillation, or in aquatic exercise settings.
- Moderate intensity corresponds to approximately 12-14 on the Borg Scale (or 4-6 on the CR-10), aligning roughly with 64-76% of maximal heart rate.
- RPE is subjective but validated. Research consistently shows strong correlations between RPE and objective physiological markers of intensity.
Example
A trainer works with a 55-year-old client on metoprolol (a beta-blocker) for high blood pressure. Because the medication suppresses heart rate, heart rate zones would be inaccurate. Instead, the trainer uses the Modified Borg Scale: RPE 4-6 for steady-state cardio ("somewhat hard — you can talk but not sing") and RPE 7-8 for short interval bursts. This ensures appropriate training intensity regardless of the medication's effect on heart rate.
This content is for educational purposes and does not replace your official NASM or ACE study materials.