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Short Research Report

Self-Rated Accuracy of Rating of Perceived Exertion-Based Load Prescription in Powerlifters

Helms, Eric R.1; Brown, Scott R.1; Cross, Matt R.1; Storey, Adam1; Cronin, John1,2; Zourdos, Michael C.3

Author Information
Journal of Strength and Conditioning Research: October 2017 - Volume 31 - Issue 10 - p 2938-2943
doi: 10.1519/JSC.0000000000002097
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Abstract

Introduction

It has been reported that there is a wide disparity of repetitions allowed at various percentages of 1 repetition maximum (1RM) among individuals (7) and large fluctuations of resistance training performance based on daily readiness (5,9). Thus, the repetitions in reserve (RIR)-based rating of perceived exertion (RPE) scale (11) was designed to autoregulate training load based on daily readiness (3) and equate effort per set across individuals. Therefore, instead of prescribing a number of repetitions at a particular percentage of 1RM, a number of repetitions can be prescribed with a target RPE i.e., 8 repetitions at an 8 RPE (2 RIR).

The RIR-based scale has specific utility because less than maximal Borg RPE ratings are sometimes given by subjects even when performing sets to failure (2); by contrast, the RIR-based scale seems especially accurate when training near to failure. Importantly, it was demonstrated that trained men and women estimated RIR accurately (an RIR error of <1) when performing sets 0–3 repetitions from failure with a predetermined load (1); however, RIR was less accurate when performing sets further from failure (1,2). In addition, RPE/RIR accuracy has been shown to improve with training experience (3). However, there is no study examining the accuracy of self-selected loads (i.e., no predetermined load) to comply with the desired RPE.

Therefore, the aim of this study was to assess nationally qualified male and female powerlifters' ability to accurately select loads resulting in a target RIR-based RPE for a single set in the squat, bench press, and deadlift on hypertrophy-, power- and strength-type sessions over 3 weeks. We hypothesized that accuracy would be the same between lifts, as similar RPE has been previously reported among the powerlifts at 1RM in powerlifters (4). In addition, we hypothesized accuracy during lower RPE hypertrophy, and power sessions (target RPE = 8) would be less than the higher RPE strength sessions (target RPE = 9). Finally, we postulated that accuracy would improve over 3 weeks, as subjects gained familiarity with this training approach.

Methods

Experimental Approach to the Problem

Competitive powerlifters performed the squat and bench press 3× per week and the deadlift 2× per week (only strength and power sessions) for 3 weeks in a daily undulating format. Weekly session order was hypertrophy-, power-, then strength-type on nonconsecutive days (i.e., Monday, Wednesday, Friday) (10). Immediately before an initial 1RM testing session, which occurred 72 hours before the first training session, the RIR-based RPE scale was shown to each participant and described in detail (11). The scale was shown to subjects after all warm-up and working sets during testing.

During training, an RPE target was provided for a specific number of repetitions on the initial working set for each lift; thus, subjects self-selected the load they believed would result in the target RPE. Only the load for the initial set was selected by the participants (subsequent sets were adjusted based on postset RPE score). Therefore, to determine RPE accuracy, differences between the target RPE and actual RPE after the initial set for each exercise were analyzed.

Subjects

Fourteen powerlifters were recruited and 12 completed the protocol; 9 men (height 1.71 ± 0.06 m; body mass 81.9 ± 12.5 kg) and 3 women (height 1.62 ± 0.08 m; body mass 59.0 ± 5.8 kg). Two (men: n = 2) dropped out due to injury or inability to complete all sessions. Inclusion criteria were as follows: (a) minimum resistance training experience 1 year; (b) meeting the New Zealand powerlifting national qualifying strength requirements in previous competition (within 1 year) or during testing (6); (c) compliance with the banned substance list of the International Powerlifting Federation (IPF) (8); (d) be between 18 and 49 years old; and (e) be free from injury/illness. All subjects were informed of potential risks and signed an informed consent document before participation (Aukland University of Technology ethics approval number 15/06).

Procedures

Rating of Perceived Exertion

The RIR-based RPE scale (i.e., RPE scores which correspond to RIR) (Figure 1) (11) was used throughout the study. The scale was shown and explained to each subject in the same exact manner before pretesting and was shown to each subject after all warm-up and working sets.

F1
Figure 1.:
Repetitions in reserve–based RPE scale. RPE = rating of perceived exertion.

Training Protocol

Three weeks of training were completed with a program similar to a previous undulating powerlifting protocol (10) in that each session had a specific goal: Monday: “hypertrophy” (8 repetitions at an 8 RPE), Wednesday: “power” (2 repetitions at an 8 RPE), and Friday: “strength” (3 repetitions at a 9 RPE). The squat and bench press were performed in all sessions, whereas deadlift was performed only on power and strength sessions to minimize injury risk and to comply with common powerlifting methods. Subjects were trained in the “offseason”, i.e., they were not in the immediate precompetition training phase. Subjects were instructed to not modify their nutrition or nutritional supplementation during the study, and all sessions for each individual were conducted at the same time of day whenever possible. In each session, lifts were performed in competition order: squat, then bench press, and then deadlift (if performed), after a dynamic warm-up and warm-up sets. There was a 5-minute rest period after the completion of a lift before the next was initiated. After each warm-up set, RPE was obtained, and after all warm-up sets, the subject was informed of the repetition and RPE target for the day. After warm-up sets, a 3-minute rest was administered, then subjects performed the working set with a self-selected load with the goal of meeting the target repetitions and RPE. Consultation of previous session data was allowed to assist load selection.

Statistical Analyses

To quantify the directionality of error, “RPE difference” (RPEDIFF) of target vs. reported RPE was recorded (reported RPE score—RPE target). Thus, negative numbers represent “undershooting” target RPE, whereas positive numbers represent an “overshoot.” Because RPE corresponds to RIR, missed repetitions counted as a full RPE score overshoot. These data are displayed in Figure 2.

F2
Figure 2.:
RPEDIFF values of powerlifters performing the squat, bench press, and deadlift over 3 weeks.

To display “absolute accuracy,” the mean absolute RPEDIFF (negative sign excluded for RPE undershoot) for each lift for each session was calculated. Thus, absolute RPEDIFF values were averaged for squat hypertrophy week 1, 2, and 3, bench press power week 1, 2, and 3, deadlift strength week 1, 2, and 3 etc., for each subject. These data are displayed in Table 1.

T1
Table 1.:
Three-week average absolute RPEDIFF values.*†

Nonparametric statistical comparisons were made using RPEDIFF values (sign included). Both RPEDIFF over and undershoot values were averaged to generate mean so that differences in directionality (under and overshooting) of accuracy could be assessed. Comparisons were made from each week, for each lift, for the same training session compared with the other lifts (i.e., squat hypertrophy vs. bench press hypertrophy). In addition, comparisons were made within the same lift, between training sessions (i.e., bench press hypertrophy vs. bench press power vs. bench press strength). Finally, comparisons were made between weeks for the same lift, during the same session to assess the effect of time (i.e., deadlift power week 1 vs. deadlift power week 2 vs. deadlift power week 3).

A Friedman test with an alpha set at 0.05 was used for comparisons between 2 variables (i.e., squat and bench press comparisons on hypertrophy sessions). When 3 variables were compared (i.e., hypertrophy vs. power vs. strength for the bench press), a Friedman test followed by a post hoc Wilcoxon signed rank test was used. A Bonferroni correction was used for 3 variable comparisons. Analysis was performed using a statistical software package (IBM SPSS Statistics 21, SPSS Inc., Chicago, IL).

Results

Rating of Perceived Exertion “Under” and “Overshoot”

Figure 2 displays RPEDIFF without the sign dropped to demonstrate RPE “over” and “undershoot” throughout the study with “X” values displaying RPEDIFF among individual subjects (darker x's signify a greater number of subjects with the same RPEDIFF).

Absolute RPEDIFF Scores

Table 1 displays RPEDIFF values, with the sign dropped, for the group and individuals to show “absolute accuracy.”

Within-Lift RPEDIFF Comparisons Between Sessions

Squat RPEDIFF comparisons between hypertrophy (−0.19 ± 0.21 RPE), power (−0.10 ± 0.45 RPE), and strength (0.01 ± 0.37 RPE) sessions were not significantly different (raw p = 0.07–0.76; Bonferroni corrected p = 0.22–0.99). Bench press RPEDIFF for hypertrophy (0.14 ± 0.44 RPE) was closer to the RPE target compared with power (−0.21 ± 0.35 RPE), but this difference only approached significance after ad hoc testing (raw p = 0.03; Bonferroni corrected p = 0.10). Bench press RPEDIFF for strength (0.15 ± 0.42 RPE) was significantly closer than power to the target RPE (raw p = 0.02; Bonferroni corrected p = 0.05). Bench press RPEDIFF for strength vs. hypertrophy was not significantly different (raw p = 0.94; Bonferroni corrected p = 0.99). Finally, deadlift RPEDIFF for strength (0.04 ± 0.41 RPE) was not significantly different than power (–0.08 ± 0.23 RPE, p = 0.16).

Within-Session RPEDIFF Comparisons Between Lifts

Bench press RPEDIFF was closer to the RPE target compared with squat on hypertrophy sessions (p = 0.02). All comparisons of RPE differences during power sessions among the lifts were nonsignificant (raw p = 0.17–0.72; Bonferroni corrected p = 0.50–0.99). Likewise, all comparisons of RPE differences during strength sessions among the lifts were nonsignificant (raw p = 0.58–0.81; Bonferroni corrected p = 0.99).

RPEDIFF Over Time

To assess whether the accuracy of load selection to reach RPE targets changed over time, RPEDIFF was assessed across weeks. There was a difference approaching statistical significance indicating that week-3 (−0.04 ± 0.26 RPE) vs. week-1 (−0.33 ± 0.39 RPE) accuracy may have improved during squat hypertrophy sessions (raw p = 0.04; Bonferroni corrected p = 0.11). Likewise, a difference approaching significance indicated that week-2 (0.08 ± 0.67 RPE) vs. week-1 (−0.46 ± 0.69 RPE) accuracy may have improved for squat in power sessions (raw p = 0.03; Bonferroni corrected p = 0.09). Week-3 RPEDIFF for squat in power sessions (0.08 ± 0.29 RPE) was significantly more accurate vs. week-1 (raw p = 0.01; Bonferroni corrected p = 0.03). All other comparisons across weeks did not approach nor reach significance after Bonferroni correction.

Discussion

The purpose of this investigation was to assess if powerlifters could accurately self-select loads corresponding to a target RPE and number of repetitions. Our first hypothesis, that RPEDIFF would be similar between lifts, was mostly supported in that the comparisons were nonsignificant during strength and power sessions. However, RPE scores for bench press were closer to the target RPE than squat during hypertrophy sessions (p = 0.02). Our second hypothesis, that RPE scores during strength sessions would be closer to the target (RPE 9) than hypertrophy and power sessions (RPE 8), was mostly unsupported as the accuracy of strength session RPE was only statistically superior to power for the bench press (Bonferroni corrected p = 0.05). Finally, our premise that reported RPE would be closer to the target over time as accuracy improved, was only true for squat hypertrophy sessions in week 3 vs. week 1 (Bonferroni corrected p = 0.03).

A potential explanation for why RPE was closer to the target for bench press compared with squat during hypertrophy sessions is that squats arguably require more technical skill and generate more systemic fatigue because of the amount of musculature involved. Thus, there is a greater chance of a technique error, causing greater RPE variability, with high repetition squats compared with the bench press. To reconcile our second hypothesis being unsupported, Hackett et al. recently reported RIR to be accurately estimated when repetitions were within 0–3 of failure (1,2), which would encompass all present target RPEs (8–9 RPE = 1–2 RIR). Regarding our final hypothesis of improvement over time with RPE, statistically there was only an improvement in the squat during power sessions (week 2 vs. 1, Bonferroni corrected p = 0.09; week 3 vs. 1, Bonferroni corrected p = 0.03), although there was also a trend for improvement during squat hypertrophy sessions (week 3 vs. 1, Bonferroni corrected p = 0.11). As previously stated, the squat arguably requires the most technical proficiency to perform. This, combined with lower target RPE on power and hypertrophy sessions relative to strength sessions, may be why a learning effect was observed only when a lower RPE was combined with the most complex lift. However, it can be observed from the data in Figure 2 (panels A, B, and C) that the spread of RPE scores tightened around the target, as the lifters progressed from weeks 1–3, with the exception of 2 outlier performances in week 3. In addition, it is possible that 3 weeks is not a long enough time frame to demonstrate improvements in RPE accuracy.

Overall, accurate loads were selected to reach the target RPE. Even when extending absolute RPEDIFF 2 SDs from the mean, values were ∼1 RPE from the target on average (Table 1). However, limitations do exist: Sets were not performed to failure (except in error when exceeding the target RPE) thus, whether RPE scores represented “true” RIR is unknown; however, it has previously been reported that intraset RIR ratings were accurate when sets were close to failure (1,2). Finally, accuracy was only examined in 1 set, thus future research should examine the ability to meet an RPE target with a self-selected load on subsequent sets once fatigue (neuromuscular and metabolic) is present.

Practical Applications

Powerlifters can select loads to reach a self-rated target RPE with precision after a familiarization session explaining and using the RPE scale. However, achieving peak accuracy levels for the squat at RPE targets below 9 may require at least 3 weeks. In addition, it seems that RPE ratings for the bench press are more accurate when performing low repetition sets closer to failure, and powerlifters are slightly better at selecting a load for an RPE target with high repetitions (8 repetitions at RPE 8) in the bench press vs. squat. However, the between-lift difference magnitude is low in that on average, powerlifters had an absolute error of 0.33 RPE, with a mean range of 0.22–0.44 RPE (Table 1). Thus, practical differences in accuracy between lifts, and sessions may be inconsequential. Practically, we recommend that RPE targets can be used for load prescription in powerlifters; however, it is unknown if untrained lifters can effectively self-select a target RPE load.

References

1. Hackett DA, Cobley S, Davies T, Michael S, Halaki M. Accuracy in estimating repetitions to failure during resistance exercise. J Strength Cond Res 31: 2162–2168, 2017.
2. Hackett DA, Johnson NA, Halaki M, Chow CM. A novel scale to assess resistance-exercise effort. J Sports Sci 30: 1405–1413, 2012.
3. Helms ER, Cronin J, Storey A, Zourdos MC. Application of the repetitions in reserve-based rating of perceived exertion scale for resistance training. Strength Cond J 38: 42–49, 2016.
4. Helms ER, Storey A, Cross MR, Brown SR, Lenetsky S, Ramsay H, Dillen C, Zourdos MC. RPE and velocity relationships for the back squat, bench press, and deadlift in powerlifters. J Strength Cond Res 31: 292–297, 2017.
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6. New Zealand Powerlifting Federation. Available at: http://www.nzpowerlifting.co.nz/. Accessed March 6, 2015.
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8. World Anti-Doping Agency. Available at: https://wada-main-prod.s3.amazonaws.com/resources/files/wada-2016-prohibited-list-summary-of-modifications-en.pdf. Accessed May 20, 2017.
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11. Zourdos MC, Klemp A, Dolan C, Quiles JM, Schau KA, Jo E, Helms E, Esgro B, Duncan S, Garcia Merino S, Blanco R. Novel resistance training-specific rating of perceived exertion scale measuring repetitions in reserve. J Strength Cond Res 30: 267–275, 2016.
Keywords:

resistance training; autoregulation; powerlifting; periodization

© 2017 National Strength and Conditioning Association