The Rate of Perceived Exertion (RPE) is a simple, yet powerful, subjective method for gauging and controlling the intensity of physical activity. Developed in the 1960s, RPE provides a numerical rating that corresponds to how hard an individual feels they are working during exercise. This tool is widely used in both cardiovascular and strength training to monitor and regulate workout difficulty in real-time. By assigning a number to your personal feeling of effort, RPE helps ensure that training aligns with specific fitness goals and your body’s daily capacity.
What is the Rate of Perceived Exertion?
The core concept of RPE is a self-assessment of the physical sensations experienced during exercise. It represents a holistic measure that integrates various internal signals from the body, including increasing heart rate, faster breathing, muscle fatigue, and sweating. RPE is a psychophysiological tool, meaning it connects the body’s physical responses with a person’s psychological interpretation of effort.
Because RPE is subjective, it differs from objective metrics like a heart rate monitor. The scale asks the individual to consider their overall feeling of effort, not just one isolated factor. Using RPE allows for an intuitive, equipment-free estimation of intensity that has proven accurate in scientific settings.
Understanding the RPE Scales
There are two primary RPE scales, each serving a slightly different purpose in fitness and exercise science.
The Borg Scale (6-20)
The original model is the Borg Rating of Perceived Exertion, which uses a range of 6 to 20. This seemingly unusual range was deliberately chosen because it correlates closely with the heart rate. Multiplying the RPE score by 10 gives an approximate heart rate (e.g., an RPE of 13 suggests about 130 beats per minute). An RPE of 6 signifies no exertion, like sitting, while an RPE of 20 represents maximal effort.
The Simplified Scale (1-10)
A more modern and commonly adopted system, particularly in strength training, is the simplified 1-10 scale. On this scale, 1 is equated with very light activity, and 10 is absolute maximal effort. For cardiovascular exercise, an RPE of 4-6 is typically a moderate, conversational pace, while 7-9 is a vigorous effort where speaking becomes difficult.
Repetitions in Reserve (RIR)
The 1-10 scale is often linked to the concept of Repetitions in Reserve (RIR), which indicates how many more repetitions a person could have completed before reaching muscular failure. This provides a direct, actionable metric for lifters to manage training load. For example, an RPE of 8 means the exerciser felt they had two repetitions left (2 RIR). An RPE of 10 signifies training to complete momentary muscle failure (0 RIR).
How to Use RPE to Guide Training
RPE is a practical tool that enables a strategy known as autoregulation, allowing exercisers to adjust their workout intensity based on how they feel on any given day. Instead of rigidly following a set weight or speed, a training program can prescribe a target RPE for a set or duration. For instance, a strength program might call for three sets of five repetitions at an RPE 8.
The lifter selects a weight that allows them to complete five reps while feeling they could have performed two more. If they feel stronger, they increase the weight to maintain the RPE 8 target. If fatigued, they decrease the weight, ensuring the intended effort level is met without excessive strain. This flexibility accounts for external factors like poor sleep, stress, or nutrition.
In endurance training, RPE can be used to maintain a consistent effort level regardless of external conditions like wind or terrain. A runner might aim for a long run at an RPE 5, which represents a pace where conversation is still relatively easy. If they encounter a hill or strong headwind, they slow down their pace to keep the RPE at 5, ensuring the training stimulus remains appropriate for the session’s goal.
RPE Compared to Other Intensity Measures
RPE offers a significant advantage over objective measures like Heart Rate (HR) or percentage of One Rep Max (%1RM) by accounting for internal variables. Objective measures provide a fixed external number, such as 150 beats per minute or a weight that is 80% of a maximum lift. These metrics do not inherently adjust for daily fluctuations in recovery, mental fatigue, or illness.
For example, a heart rate of 150 beats per minute might feel like a moderate RPE 6 on a well-rested day, but feel like a difficult RPE 8 following poor sleep. RPE captures this difference in perceived difficulty. While HR monitors and %1RM are valuable for precise physiological tracking, RPE ensures the intensity is appropriate for the body’s state that day.
Percentage-based training also faces challenges because the relationship between a percentage of 1RM and possible repetitions varies widely between individuals. RPE, especially when linked to Repetitions in Reserve, provides a personalized system for managing fatigue and training load. This makes RPE a powerful tool for preventing overtraining while ensuring a sufficient training stimulus is applied.