Is Rate of Perceived Exertion a Useful Strength Training Tool?
For runners and other endurance athletes, rate of perceived exertion (RPE) is a valuable metric. Training programs often have athletes use RPE to self-regulate their efforts. For instance, a program might ask an athlete to run a given distance at a “moderate pace,” defined as an RPE of 5 or 6 on a 10-point scale. As one might expect, the RPE for endurance workouts depends on intensity, duration, the athlete’s fitness, and similar factors.
The use of RPE in resistance exercise is less well-established. In a study published in the Journal of Strength and Conditioning Research, Marc Testa, Timothy D. Noakes, and François-Denis Desgorces explained that several factors may make RPE less useful for self-regulation of resistance workouts. One is simply the nature of resistance training: strength response is non-linear, and athletes often train at substantial fractions of their maximum capacity. While a runner might be able to extend a workout from 10 miles to 11 without difficulty, most lifters would find a 10% increase in load to be much more challenging.
A second factor is that low volume, high intensity (measured by % of 1RM) resistance workouts are qualitatively different from high volume, low intensity workouts. It is not clear that comparing RPE between the two is meaningful. This point will seem obvious to CrossFitters: do five heavy clean and jerk doubles with ample rest between sets require a greater RPE than 30 light clean and jerks done as rapidly as possible? Which workout should an athlete do on an “easy” day?
As this example illustrates, a third factor is the imperfect correlation between maximum strength and strength endurance. Strength endurance - defined as maximum reps at a given fraction of 1RM - can vary widely between individuals with similar maximum strength.
In order to evaluate the factors contributing to RPE for resistance exercise, the researchers measured the strength and strength endurance of 80 college-age athletes (55 men and 25 women) from a variety of different sports. Participants had varying amounts of experience with resistance training, and were divided into three cohorts:
- Highly trained (29 men and 10 women), with an average of 24 strength workouts in the last three months.
- Moderately trained (26 men and 8 women), with an average of 9 strength workouts in the last three months.
- Novices (18 men and 7 women), with no previous resistance training experience.
Before beginning the study, the novices received technical training in bench press technique. Then, researchers tested the 1RM bench press for all participants. As one would expect, training experience and gender correlated with bench press strength. In a second session, one week after the first, participants tested their maximum reps at both heavy (about 90% of 1RM) and moderate (about 67% of 1RM) loads. The results from the first two sessions were used to assign weights and repetitions for the third session, which tested RPE.
In the third session, one week after the second, participants performed a total of four bench press sets: two sets at low reps, with heavy and moderate weights, and two sets at high reps, also at heavy and moderate weights. They were asked to report their RPE based on a standard 10-point scale. Lifts were performed “blind,” in that the weights were covered with plastic bags filled with Styrofoam to obscure the amount of weight being lifted.
Low Rep Test Results
For low reps, the study found no relationship between RPE and gender, total load, or absolute intensity (% of 1RM). However, in the highly trained group, there was a correlation between RPE and relative volume (% of maximum reps at that weight). This relationship was not seen in the other groups. The authors suspect that more highly trained individuals either receive more sensory feedback or are more able to interpret the sensory signals that they receive.
High Rep Test Results
In the high rep sets, this effect was seen in all three groups. Higher relative volume led to increased RPE. From a programming standpoint, this means that the predictive value of RPE increases with volume for resistance exercise. So, using RPE as a tool for self-regulation would be more applicable in sessions involving higher numbers of reps.
Using the RPE 1-10 scale, while not a sufficiently accurate tool for self-regulation of low volume workouts, may have value for higher volume training. For instance, changes in RPE give one possible measure of changes in the athlete’s ability to repeat lifts. The authors emphasize, however, that RPE-based assessments cannot replace direct testing of maximal strength or strength endurance.
1. Marc Testa, Timothy D. Noakes, and François-Denis Desgorces, “Training State Improves The Relationship Between Rating Of Perceived Exertion And Relative Exercise Volume During Resistance Exercises,” J. Strength and Cond. Res., 26(11), 2990-2996 (2012)
Photo courtesy of Shutterstock.