Topics in Stroke Rehabilitation
ISSN: 1074-9357 (Print) 1945-5119 (Online) Journal homepage: http://www.tandfonline.com/loi/ytsr20
Validity of Rating of Perceived Exertion Ranges in Individuals in the Subacute Stage of Stroke Recovery Michael Sage, Laura E. Middleton, Ada Tang, Kathryn M. Sibley, Dina Brooks & William McIlroy To cite this article: Michael Sage, Laura E. Middleton, Ada Tang, Kathryn M. Sibley, Dina Brooks & William McIlroy (2013) Validity of Rating of Perceived Exertion Ranges in Individuals in the Subacute Stage of Stroke Recovery, Topics in Stroke Rehabilitation, 20:6, 519-527 To link to this article: http://dx.doi.org/10.1310/tsr2006-519
Published online: 05 Jan 2015.
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Michael Sage, MSc,1,2 Laura E. Middleton, PhD,2,3,4 Ada Tang, PhD,5,6 Kathryn M. Sibley, PhD,2 Dina Brooks, PhD,1,2,7 and William McIlroy, PhD1,2,3,4 1 Graduate Department of Rehabilitation Studies, University of Toronto, Toronto, Canada; 2Toronto Rehabilitation Institute, Toronto, Canada; 3Department of Kinesiology, University of Waterloo, Waterloo, Canada; 4Heart and Stroke Foundation Centre for Stroke Recovery, Sunnybrook Research Institute, Toronto, Canada; 5Department of Physical Therapy, University of British Columbia, Vancouver, Canada; 6 GF Strong Rehabilitation Research Lab, Vancouver, Canada; 7Department of Physical Therapy, University of Toronto, Toronto, Canada
Background: Rating of perceived exertion (RPE) is used to monitor or prescribe workload of exercise, but its utility among individuals with a stroke remains in question. Objective: To examine the validity of RPE at multiple percentages of peak aerobic capacity (Vo2peak) in individuals in the subacute stage of stroke recovery. Methods: Thirty-seven patients with stroke in the subacute stage of recovery from an inpatient rehabilitation institute completed a graded maximal exercise test on a semi-recumbent cycle ergometer. Respiratory gas exchange was monitored for analysis of Vo2, while heart rate and RPE (Borg CR10 Scale) were measured at the end of each minute. RPE was compared with expected ranges when at 60%, 70%, and 80% of Vo2peak. Post hoc analyses were performed to determine whether patient characteristics differed between participants who fell within and outside the expected RPE range at 80% of Vo2peak. Results: Median (interquartile range) RPE at 60%, 70%, and 80% Vo2peak were 3.0 (3.0-3.5), 3.0 (3.0-5.0), and 4.75 (3.0-5.75), respectively; 76.2%, 69.0%, and 38.9% of participants fell into the expected RPE range at each intensity. Patient characteristics were similar between participants who fell within and outside the expected RPE range at 80% Vo2peak. Conclusion: RPE appears to be a reasonable indicator of exercise intensity after stroke at moderate (60%-70% Vo2peak) but not high-intensity exercise (80% Vo2peak). This conclusion is based on the high degree of between-subject variability in RPE at 80% Vo2peak. Future research should identify whether RPE can be adapted to accurately capture exertion during high-intensity exercise after stroke. Key words: exercise, rating of perceived exertion, stroke, rehabilitation
A
erobic capacity is often reduced after stroke, which restricts a person’s ability to complete activities of daily living and function independently.1,2 Accordingly, aerobic exercise is recommended in best practice guidelines to improve aerobic capacity, walking speed, and functional independence after stroke.3 Aerobic exercise is prescribed and monitored by frequency, duration, and intensity. Although it is relatively simple to track frequency and duration, the evaluation of exercise intensity after stroke can be challenging. The American College of Sports Medicine (ACSM) guidelines recommend using heart rate (HR) or rating of perceived exertion (RPE).4 HR is preferred because it is a direct measure of physiologic intensity. However, RPE is recommended when HR response to exercise is not predictable, practical, or feasible. Because some medications frequently prescribed after a stroke, such as betablockers, can alter the HR response to exercise,
RPE is often used to prescribe and monitor exercise intensity. Although RPE is commonly used, its suitability for monitoring exercise intensity in the stroke population is unknown. RPE was developed to rate the subjective degree of heaviness or strain experienced in physical activity.5 Within a person and across workloads and work types, RPE correlates well with physiological measures of exercise intensity including HR, oxygen consumption, blood lactate concentration, and respiratory rate.6 However, between participants, RPE at a given physiological intensity can be highly variable and depends on factors such as age and exercise modality.7 In studies of RPE responses to exercise among healthy Top Stroke Rehabil 2013;20(6):519–527 © 2013 Thomas Land Publishers, Inc. www.strokejournal.com doi: 10.1310/tsr2006-519
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and cardiac populations, approximately two-thirds of participants report RPE within the expected range at moderate intensities (11-14 on the Borg RPE 15-point scale).8,9 At higher intensities, however, only half of patients with cardiac disease report RPE within the expected range (14-17 on the Borg RPE scale) compared with nearly 70% of healthy individuals. Therefore, RPE appears valid in healthy populations, but its validity among individuals with clinical conditions is less clear. Concern about the use of RPE to estimate workload intensity may be accentuated in people with stroke. Stroke-related impairments (physical or cognitive) may alter RPE for a given exercise intensity. In a study focusing on graded exercise test performance among people with stroke, a positive association was found between the ability to achieve maximal physiological effort (defined by age-predicted maximal HR) and motor and cognitive function. Moreover, RPE values provided at the end of the tests were higher among persons who were not able achieve age-predicted maximal HR, suggesting a mismatch between reported and actual exertion.10 Additionally, in the chronic phase of stroke recovery, individuals achieved significantly lower HR than predicted on the basis of RPE during walk tests.11 Furthermore, people with stroke who rested during a 6-minute walk test (6MWT) reported significantly higher RPE than those who did not rest, despite comparable HR response, which suggests an inconsistent association between RPE and physiologic effort.12 These findings suggest that RPE may not be a valid index of intensity of exercise after stroke. Understanding the validity of RPE ranges for exercise intensity prescription is particularly important in the early stages of stroke recovery when deficits are most pronounced. This is an important phase in which to implement aerobic training programs and requires care in prescription and monitoring of intensity for safety purposes. Despite the common use of RPE for prescription in clinical and community settings, RPE ranges have not yet been validated against physiological measures of exercise intensity among patients with stroke. It is reasonable to expect that people with stroke may report different or more variable RPE for a given exercise intensity, similar to individuals with cardiac disease. Consequently, the primary
objective of this study was to examine the validity of expected RPE ranges at 60%, 70%, and 80% of peak aerobic capacity (Vo2peak) in patients with stroke in the subacute stage of recovery. Methods This project is a secondary analysis of graded maximal exercise tests results from a subacute stroke population in Toronto, Ontario, Canada.2 The study was approved by the ethics board at the Toronto Rehabilitation Institute and the University of Toronto. All participants provided written informed consent. Subjects
Participants were recruited from the inpatient stroke rehabilitation program at the Toronto Rehabilitation Institute. Participants were medically stable and in the subacute stage of stroke recovery (80% Vo2peak; one was excluded because the maximal exercise test was too short to match RPE to 60%, 70%, or 80% of Vo2peak; and 1 was excluded because equipment malfunctioned during the test, leaving a sample size of 37. Maximal exercise test
All participants completed a graded maximal exercise test on a semi-recumbent cycle ergometer (Biodex Medical Systems, Inc., Shirley, NY). The test protocol was designed to accommodate the strength and fatigability of patients in the subacute phase of stroke recovery, with a target total test
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RPE Validity in Subacute Stroke
time of 8 to 10 minutes.2 Participants warmed up for 2 minutes at 10 W and then immediately performed the exercise test. The exercise test included a 5-W increase in work rate every minute with a target cadence of 50 rpm throughout. If necessary, the foot on the participant’s hemiparetic side was secured to the pedal. The participant could terminate the test at any time. Otherwise, the test was conducted and terminated according to ACSM criteria14 or was terminated if a participant was unable to maintain 50 rpm despite cueing. The reason for termination was recorded by the researcher at the completion of the test. Blood pressure, HR, and 5-lead electrocardiogram readings were monitored throughout the test to ensure safety, and a physician was present when deemed medically necessary. Respiratory gas exchange was monitored with a metabolic cart (AEI Technologies, Inc., Pittsburgh, PA). To minimize variability in peak ventilation values, respiratory gas exchange was measured in 30-second intervals according to American Thoracic Society/American College of Chest Physicians guidelines.15 Vo2peak was defined as the highest value reached during the exercise test, from which 60%, 70%, and 80% Vo2peak values were calculated. For the purpose of determining whether participants achieved maximal exertion levels, test results were evaluated for a plateau in Vo2, a respiratory exchange ratio (RER) greater than 1.0, and a peak HR within 10 beats/min (bpm) of age-calculated maximum (208 – [0.7 ⫻ Age]). RPE was reported every minute using the Borg Category Ratio Scale (CR-10), a 10-point RPE scale.16 In some cases, RPE was not available for one or more submaximal intensities. RPE was not available if an individual was already near peak levels in the first exercise stage (10 W resistance) or if there was no reported RPE that closely corresponded to one of the calculated intensities (60%, 70%, or 80% Vo2peak). Other measurements
Participants reported demographic variables and medications. Stroke characteristics including date, type, and location were extracted from the medical records. In addition, a number of measures regarding stroke-related deficits were completed. For
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example, stroke-related impairment was assessed using the National Institutes of Health Stroke Scale (NIHSS).17 Functional ability was measured using the Functional Independence Measure (FIM).18 Leg motor impairment was assessed using the ChedokeMcMaster Stroke Assessment (CMSA).19 Expected RPE ranges
Previous research analyzing the relationship between physiologic variables and perceived exertion relied on the 15-point RPE scale. To the best of our knowledge, this is the first report of this nature to use the 10-point RPE scale. The 10-point scale was developed as a simpler category scale with ratio properties.5 It was used because patients with stroke may have an easier time providing a rating of exertion from 1 to 10 as opposed to the more traditional rating on the Borg 15-point RPE scale. Expected RPE ranges for the 10-point RPE scale (CR-10) were generated on the basis of established RPE ranges from the Borg 15-point RPE scale by matching the word anchors for each exercise intensity range.8,20 For example, an RPE range of 11 to 14 on the 15-point RPE scale has been used to represent 60% intensity using maximal HR reserve.8 An RPE rating of 11 on the 15-point scale has a word anchor “fairly light” and matches a rating of 2 on the CR-10, which has the word anchor “weak (light).” An RPE of 14 on the 15-point RPE scale falls between the word anchors “somewhat hard” and “hard” and matches a rating of 4 on the CR-10, which has the word anchor “somewhat strong.”7 Using this technique, we established expected RPE ranges from the CR-10 of 2 to 4 for 60%, 3 to 5 for 70%, and 5 to 7 for 80% of Vo2peak. Statistical analysis
Pa rticipant characteristics were described by mean (SD) or percent (n), as appropriate. Frequency distributions were generated to show the variability of RPE at 60%, 70%, and 80% of Vo2peak. The RPE at each intensity was described by median (interquartile range) and by the proportion of participants falling in the expected RPE range. The proportion of participants falling within versus outside the expected RPE range was compared between intensities using the chi-square test.
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Because considerably fewer participants fell into the expected RPE range at 80% of Vo2peak than at 60% or 70% of Vo2peak in this study and in comparison with healthy participants in a previous study,8 we conducted a secondary analysis to determine whether participant characteristics were associated with the likelihood of reporting within the expected RPE range using chi-square tests or t tests as appropriate. All statistical analyses were conducted using SAS software version 9.1.3 (SAS Institute, Inc., Cary, NC). Results Our study sample (n = 37) had an average age of 65.7 years, was 46.0% female, and completed the exercise test an average of 14.5 days post stroke. See Table 1 for a full account of participant demographics, comorbidities, medications, and stroke characteristics. Mean Vo2peak was 11.3 (±2.5) mL·kg-1·min-1, peak RER was 0.99 (±.09), peak HR was 107.3 (±23.8) bpm, and peak RPE was 6.7 (±2.7). At least 1 of the ACSM criteria for maximal exertion was achieved by 24 of 37 individuals (64.8%), with the majority (18 of 37) achieving an RER ≥1. Among those who did not meet ACSM criteria, the most common reasons for stopping the test early were related to functional impairments including leg effort (6 of 13) and inability to maintain 50 rpm (2 of 13). At 60% and 70% of Vo2peak, more than two-thirds of participants reported an RPE within the expected range (Figure 1). However, fewer than half of the participants reported an RPE within the expected
Table 1. Baseline characteristics of study participants (n = 37) Characteristic
Mean (SD) or n (%)
Age, years Sex (% female) Type of stroke (% ischemic) Stroke hemisphere (% left) Time since stroke, days Medications Beta-blockers (% yes) ACE inhibitors (% yes) Comorbidities Hypertension Dyslipidemia Diabetes Coronary artery disease History of smoking Previous stroke or TIA NIHSS CMSA leg CMSA foot FIM
65.7 (14.3) 17 (46.0%) 27 (75%) 15 (41.7%) 14.5 (10.2) 9 (24.3%) 18 (48.6%) 18 (64.9%) 14 (37.8%) 5 (13.5%) 9 (24.3%) 14 (37.8%) 9 (24.3%) 4.6 (2.4) 4.7 (1.2) 4.0 (1.2) 86.7 (15.8)
Note: ACE = angiotensin-converting enzyme; CMSA = Chedoke-McMaster Stroke Assessment; FIM = Functional Independence Measure; NIHSS = National Institutes of Health Stroke Scale; TIA = transient ischemic attack.
range of 5 to 7 at 80% of Vo2peak (Table 2). In light of this difference, we conducted follow-up analyses to determine whether participant characteristics were associated with the likelihood of falling within versus outside of the expected RPE range at 80% of Vo2peak. However, no differences in participant characteristics were found between subjects who did and those who did not report within the expected RPE range at 80% of Vo2peak (Table 3).
Table 2. Mean RPE and percentage in the expected range at 60%, 70%, and 80% of Vo2peak and corresponding heart rate and workload (median, range) Percent of peak Vo2
Median HR, bpm (range)
Median workload, W (range)
Expected RPE range
Percent reporting (n)a
Median RPE (IQR)
Percent within range (n)
60% 70% 80%
82 (60-112) 86 (52-122) 96 (57-133)
20 (5-30) 20 (10-40) 30 (10-65)
2-4 3-5 5-7
56.8% (21) 78.4% (29) 97.3% (36)
3.0 (3.0–3.5) 3.0 (3.0–5.0) 4.75 (3.0–5.75)
76.2% (16) 69.0% (20) 38.9% (14)*
Note: HR = heart rate; IQR = interquartile range; RPE = rating of perceived exertion; Vo2peak = peak aerobic capacity. a This column indicates the percentage and number of participants that provided an RPE report at the corresponding intensity. Not all participants reported RPE at all 3 intensities, generally because the baseline intensity was above 60% or 70% of their Vo2peak. *P < .05 compared with proportion at 60% of peak Vo2.
RPE Validity in Subacute Stroke
60.0%
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60% Peak VO2
% of Total
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80% Peak VO2
60.0% 50.0% % of Total
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0.0%
40.0% 30.0% 20.0% 10.0% 0.0% 0
1
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5 RPE
Figure 1. Histograms displaying percentage of people reporting each RPE at 60%, 70%, and 80% of Vo2peak. Broken lines mark expected RPE range for each intensity. Note that the majority of people fall within the expected range at 60% and 70% of Vo2peak; at 80% of Vo2peak, fewer than half of the people are within the expected range.
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Table 3. Comparisons between subgroups of participants providing RPE values inside or outside the expected range at 80% of peak Vo2 (RPE: 5-7)
Age, years Sex (% female) Heart rate, bpm Work rate, W Type of stroke (% ischemic) Side of stroke (% left) Time since stroke, days ≥1 ACSM criteria for Vo2max (% yes) Peak Vo2, mL/kg/min CMSA leg CMSA foot NIHSS FIM
Within expected RPE range (n=14)
Outside expected RPE range (n=22)
P*
66.1 (10.4) 4 (28.6%) 97.9 (21.4) 34.3 (10.0) 12 (85.7%) 5 (38.5%) 15.2 (15.4) 10 (71.4%) 11.7 (1.9) 4.6 (1.2) 4.0 (1.4) 5.4 (3.0) 88.1 (17.5)
62.8 (16.0) 12 (54.5%) 93.4 (13.8) 25.9 (14.4) 14 (66.7%) 9 (40.9%) 14.0 (5.7) 14 (63.6%) 11.4 (2.7) 4.8 (1.2) 4.0 (1.2) 4.0 (1.9) 86.0 (15.3)
.49 .13 .14 .20 .32 .44 .75 .59 .72 .63 1.00 .13 .72
Note: Values are expressed as mean (SD) or n (%). ACSM = American College of Sports Medicine; CMSA = Chedoke-McMaster Stroke Assessment; FIM = Functional Independence Measure; NIHSS = National Institutes of Health Stroke Scale; RPE = Rating of Perceived Exertion; Vo2max = maximum oxygen consumption. *P < .05 for difference between groups.
Discussion To the best of our knowledge, this is the first study to examine the validity of RPE ranges against a physiological measure of exercise intensity among individuals in the early stage of stroke recovery in inpatient rehabilitation. The majority of participants reported within the expected RPE ranges during moderate-intensity exercise but not during high-intensity exercise. We could not identify any differences in participant characteristics between persons reporting within versus outside the expected RPE range at high intensity. Our data support the view that RPE is appropriate for prescribing and monitoring lowto moderate-intensity exercise among most people after stroke but not for prescribing high-intensity exercise (≥80% Vo2peak). In this study, approximately two-thirds of people in the subacute stage of stroke recovery reported RPE within the expected range at moderate exercise intensities (60% and 70% of Vo2peak), but fewer than 40% reported RPE within the expected range at higher exercise intensities (80% of Vo2peak). These results are
consistent with findings from a prior study of healthy and cardiac populations, 8 in which nearly 70% of patients with cardiac disease reported within expected RPE ranges during moderate-intensity exercise, but fewer than half reported within expected RPE ranges at high intensities. In contrast, the proportion of healthy participants reporting within expected RPE ranges remained above 60% at all exercise intensities.8 Together, these results suggest that RPE in clinical populations may not be a valid indicator of physiological work during higher intensity exercise. That healthy participants are equally likely to report within expected RPE ranges at moderateand high-intensity exercise suggests that health status may affect RPE variability at higher intensities.8,9 One reason for the increased RPE variability among clinical populations could be that fewer participants reach true maximal aerobic capacity. Two-thirds of our population did meet at least one ACSM criteria for maximal Vo2; however, the maximal work rate appeared to be restrained by functional impairments rather than aerobic
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RPE Validity in Subacute Stroke
capacity in our sample, because 25 of 37 (67.6%) tests were stopped because of leg effort or inability to maintain 50 rpm. If RPE is valid for a percentage of maximal Vo2 rather than a percentage of maximal work capacity, then it would be reasonable for RPE to be underreported for people stopping because of functional rather than aerobic reasons. In our sample, half of the participants reported below the expected RPE range at 80% of Vo2peak. It is important to note, however, that presence of functional impairment and failure to meet ACSM criteria did not predict reporting within or outside of the expected RPE range. In contrast to the results of this study, Tang et al10 observed higher RPE values among individuals who were unable to achieve maximal effort on a graded exercise test after stroke, which was in turn related to level of cognition and motor impairment. Individuals with impaired cognitive abilities may have an altered perception of maximal effort during exercise tests and thus may overreport exertion. Nonetheless, these findings suggest that the variability of RPE reports at high intensities after stroke may be due to a complex interaction of several factors that may or may not be related to cardiopulmonary function. A final reason for reporting outside the expected RPE range may be inactivity before the stroke. Stroke and cardiac populations may be more likely to have a history of inactivity relative to healthy populations.21,22 If previously inactive, these populations may not be able to judge their personal physical exertion relative to their maximum capacity. Participants who reported outside the expected RPE range during highintensity exercise had HRs comparable to those of participants who reported within the expected range, even though the majority reported RPE below the expected range. Although the influence of inactivity before the medical event in clinical populations is unclear, inactivity does not influence RPE reporting in healthy populations; active and inactive individuals report similar RPE at ventilatory threshold despite large differences in Vo2.23 Thus, a history of inactivity is not likely to be the main factor leading to variable RPE reporting by patients with stroke but may be one of several factors that together confound perceived exertion in stroke populations.
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Even though our results suggest that RPE ranges are similarly valid for stroke populations and healthy populations at moderate intensities, RPE can be highly variable. Two-thirds of our sample reported within the expected 3-point range, but the range of ratings of perceived exertion was wide at each intensity (Figure 1). Additionally, the median RPE at 60% and 70% Vo2peak were identical. Given these findings, we suggest that RPE and physiological variables (eg,, HR, blood pressure, Vo2) be used in conjunction to monitor exercise intensity when possible. However, exercise monitoring and prescription based solely on RPE at moderate exercise intensity does appear to be sufficient for many people. Study limitations
Eight participants were excluded because the first stage of the maximal exercise test was already >80% Vo2peak. Thus, our results may not be generalizable to the least fit individuals. In addition, 23 participants were missing an RPE for one of the exercise intensities. These missing data generally occurred if the Vo2 during warm-up was greater than 60%, 70%, or 80% of calculated Vo2peak, and, as such, it is possible that sample bias influenced our findings. However, it is worth noting that post hoc analyses that included only people with RPE at all 3 intensities confirmed our results. Thus, the loss of individuals and smaller sample size likely did not alter the findings of this study. However, our moderate sample size may have been too small to detect associations between participant characteristics and RPE reporting. As discussed previously, several participants may not have achieved their true physiologic maximum Vo2, which would influence RPE and the proportion of participants reporting within expected RPE ranges. It is unclear whether the observed relationships between RPE and Vo2 ranges extend to individuals in the chronic stage of stroke recovery. Given that our results are similar to findings in other clinical populations and that participant characteristics were not associated with RPE validity, we anticipate that our findings would be replicated in a chronic stroke population; however, future research is needed to confirm this proposition.
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Conclusions
RPE is frequently used to prescribe exercise intensity in clinical populations in which HR may be variable, such as patients with stroke. However, the validity of RPE ranges among individuals post stroke has not previously been examined. In our study, RPE ranges were valid at moderate exercise intensities and therefore could be considered a practical and valid method for prescribing and monitoring exercise intensity clinically among most patients with stroke. Some clinicians and researchers are now exploring the use of interval training in clinical populations. Among our participants, however, RPE was highly variable during higher intensity exercise, likely because some individuals with stroke-associated functional impairment had difficulty achieving true maximal aerobic capacity. This has important clinical implications; RPE should not be relied on as the sole indicator of physiological exercise intensity at higher intensities among people with stroke.
Future studies should aim to determine whether specific stroke characteristics (eg, functional impairment, cognitive status) influence the validity of RPE reporting. Acknowledgments Conflicts of interest: The authors declare no conflict of interest. Financial support/disclosures: M. Sage is supported by Heart and Stroke Foundation Doctoral Research Award. Dr. Middleton was supported by a Canadian Institute of Health Research fellowship. Dr. Tang is supported by fellowships through the Canadian Institute of Health Research and Michael Smith Foundation for Health Research. Dr. Sibley is supported by a Canadian Institute of Health Research fellowship and the Toronto Rehabilitation Institute. Dr. Brooks holds a Canada Research Chair (Tier 2). Dr. McIlroy holds a University Research Chair.
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ISSN: 1074-9357 (Print) 1945-5119 (Online) Journal homepage: http://www.tandfonline.com/loi/ytsr20
Validity of Rating of Perceived Exertion Ranges in Individuals in the Subacute Stage of Stroke Recovery Michael Sage, Laura E. Middleton, Ada Tang, Kathryn M. Sibley, Dina Brooks & William McIlroy To cite this article: Michael Sage, Laura E. Middleton, Ada Tang, Kathryn M. Sibley, Dina Brooks & William McIlroy (2013) Validity of Rating of Perceived Exertion Ranges in Individuals in the Subacute Stage of Stroke Recovery, Topics in Stroke Rehabilitation, 20:6, 519-527 To link to this article: http://dx.doi.org/10.1310/tsr2006-519
Published online: 05 Jan 2015.
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Citing articles: 2 View citing articles
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Date: 24 March 2016, At: 08:55
Grand Rounds
Validity of Rating of Perceived Exertion Ranges in Individuals in the Subacute Stage of Stroke Recovery Downloaded by [Library Services City University London] at 08:55 24 March 2016
Michael Sage, MSc,1,2 Laura E. Middleton, PhD,2,3,4 Ada Tang, PhD,5,6 Kathryn M. Sibley, PhD,2 Dina Brooks, PhD,1,2,7 and William McIlroy, PhD1,2,3,4 1 Graduate Department of Rehabilitation Studies, University of Toronto, Toronto, Canada; 2Toronto Rehabilitation Institute, Toronto, Canada; 3Department of Kinesiology, University of Waterloo, Waterloo, Canada; 4Heart and Stroke Foundation Centre for Stroke Recovery, Sunnybrook Research Institute, Toronto, Canada; 5Department of Physical Therapy, University of British Columbia, Vancouver, Canada; 6 GF Strong Rehabilitation Research Lab, Vancouver, Canada; 7Department of Physical Therapy, University of Toronto, Toronto, Canada
Background: Rating of perceived exertion (RPE) is used to monitor or prescribe workload of exercise, but its utility among individuals with a stroke remains in question. Objective: To examine the validity of RPE at multiple percentages of peak aerobic capacity (Vo2peak) in individuals in the subacute stage of stroke recovery. Methods: Thirty-seven patients with stroke in the subacute stage of recovery from an inpatient rehabilitation institute completed a graded maximal exercise test on a semi-recumbent cycle ergometer. Respiratory gas exchange was monitored for analysis of Vo2, while heart rate and RPE (Borg CR10 Scale) were measured at the end of each minute. RPE was compared with expected ranges when at 60%, 70%, and 80% of Vo2peak. Post hoc analyses were performed to determine whether patient characteristics differed between participants who fell within and outside the expected RPE range at 80% of Vo2peak. Results: Median (interquartile range) RPE at 60%, 70%, and 80% Vo2peak were 3.0 (3.0-3.5), 3.0 (3.0-5.0), and 4.75 (3.0-5.75), respectively; 76.2%, 69.0%, and 38.9% of participants fell into the expected RPE range at each intensity. Patient characteristics were similar between participants who fell within and outside the expected RPE range at 80% Vo2peak. Conclusion: RPE appears to be a reasonable indicator of exercise intensity after stroke at moderate (60%-70% Vo2peak) but not high-intensity exercise (80% Vo2peak). This conclusion is based on the high degree of between-subject variability in RPE at 80% Vo2peak. Future research should identify whether RPE can be adapted to accurately capture exertion during high-intensity exercise after stroke. Key words: exercise, rating of perceived exertion, stroke, rehabilitation
A
erobic capacity is often reduced after stroke, which restricts a person’s ability to complete activities of daily living and function independently.1,2 Accordingly, aerobic exercise is recommended in best practice guidelines to improve aerobic capacity, walking speed, and functional independence after stroke.3 Aerobic exercise is prescribed and monitored by frequency, duration, and intensity. Although it is relatively simple to track frequency and duration, the evaluation of exercise intensity after stroke can be challenging. The American College of Sports Medicine (ACSM) guidelines recommend using heart rate (HR) or rating of perceived exertion (RPE).4 HR is preferred because it is a direct measure of physiologic intensity. However, RPE is recommended when HR response to exercise is not predictable, practical, or feasible. Because some medications frequently prescribed after a stroke, such as betablockers, can alter the HR response to exercise,
RPE is often used to prescribe and monitor exercise intensity. Although RPE is commonly used, its suitability for monitoring exercise intensity in the stroke population is unknown. RPE was developed to rate the subjective degree of heaviness or strain experienced in physical activity.5 Within a person and across workloads and work types, RPE correlates well with physiological measures of exercise intensity including HR, oxygen consumption, blood lactate concentration, and respiratory rate.6 However, between participants, RPE at a given physiological intensity can be highly variable and depends on factors such as age and exercise modality.7 In studies of RPE responses to exercise among healthy Top Stroke Rehabil 2013;20(6):519–527 © 2013 Thomas Land Publishers, Inc. www.strokejournal.com doi: 10.1310/tsr2006-519
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and cardiac populations, approximately two-thirds of participants report RPE within the expected range at moderate intensities (11-14 on the Borg RPE 15-point scale).8,9 At higher intensities, however, only half of patients with cardiac disease report RPE within the expected range (14-17 on the Borg RPE scale) compared with nearly 70% of healthy individuals. Therefore, RPE appears valid in healthy populations, but its validity among individuals with clinical conditions is less clear. Concern about the use of RPE to estimate workload intensity may be accentuated in people with stroke. Stroke-related impairments (physical or cognitive) may alter RPE for a given exercise intensity. In a study focusing on graded exercise test performance among people with stroke, a positive association was found between the ability to achieve maximal physiological effort (defined by age-predicted maximal HR) and motor and cognitive function. Moreover, RPE values provided at the end of the tests were higher among persons who were not able achieve age-predicted maximal HR, suggesting a mismatch between reported and actual exertion.10 Additionally, in the chronic phase of stroke recovery, individuals achieved significantly lower HR than predicted on the basis of RPE during walk tests.11 Furthermore, people with stroke who rested during a 6-minute walk test (6MWT) reported significantly higher RPE than those who did not rest, despite comparable HR response, which suggests an inconsistent association between RPE and physiologic effort.12 These findings suggest that RPE may not be a valid index of intensity of exercise after stroke. Understanding the validity of RPE ranges for exercise intensity prescription is particularly important in the early stages of stroke recovery when deficits are most pronounced. This is an important phase in which to implement aerobic training programs and requires care in prescription and monitoring of intensity for safety purposes. Despite the common use of RPE for prescription in clinical and community settings, RPE ranges have not yet been validated against physiological measures of exercise intensity among patients with stroke. It is reasonable to expect that people with stroke may report different or more variable RPE for a given exercise intensity, similar to individuals with cardiac disease. Consequently, the primary
objective of this study was to examine the validity of expected RPE ranges at 60%, 70%, and 80% of peak aerobic capacity (Vo2peak) in patients with stroke in the subacute stage of recovery. Methods This project is a secondary analysis of graded maximal exercise tests results from a subacute stroke population in Toronto, Ontario, Canada.2 The study was approved by the ethics board at the Toronto Rehabilitation Institute and the University of Toronto. All participants provided written informed consent. Subjects
Participants were recruited from the inpatient stroke rehabilitation program at the Toronto Rehabilitation Institute. Participants were medically stable and in the subacute stage of stroke recovery (80% Vo2peak; one was excluded because the maximal exercise test was too short to match RPE to 60%, 70%, or 80% of Vo2peak; and 1 was excluded because equipment malfunctioned during the test, leaving a sample size of 37. Maximal exercise test
All participants completed a graded maximal exercise test on a semi-recumbent cycle ergometer (Biodex Medical Systems, Inc., Shirley, NY). The test protocol was designed to accommodate the strength and fatigability of patients in the subacute phase of stroke recovery, with a target total test
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RPE Validity in Subacute Stroke
time of 8 to 10 minutes.2 Participants warmed up for 2 minutes at 10 W and then immediately performed the exercise test. The exercise test included a 5-W increase in work rate every minute with a target cadence of 50 rpm throughout. If necessary, the foot on the participant’s hemiparetic side was secured to the pedal. The participant could terminate the test at any time. Otherwise, the test was conducted and terminated according to ACSM criteria14 or was terminated if a participant was unable to maintain 50 rpm despite cueing. The reason for termination was recorded by the researcher at the completion of the test. Blood pressure, HR, and 5-lead electrocardiogram readings were monitored throughout the test to ensure safety, and a physician was present when deemed medically necessary. Respiratory gas exchange was monitored with a metabolic cart (AEI Technologies, Inc., Pittsburgh, PA). To minimize variability in peak ventilation values, respiratory gas exchange was measured in 30-second intervals according to American Thoracic Society/American College of Chest Physicians guidelines.15 Vo2peak was defined as the highest value reached during the exercise test, from which 60%, 70%, and 80% Vo2peak values were calculated. For the purpose of determining whether participants achieved maximal exertion levels, test results were evaluated for a plateau in Vo2, a respiratory exchange ratio (RER) greater than 1.0, and a peak HR within 10 beats/min (bpm) of age-calculated maximum (208 – [0.7 ⫻ Age]). RPE was reported every minute using the Borg Category Ratio Scale (CR-10), a 10-point RPE scale.16 In some cases, RPE was not available for one or more submaximal intensities. RPE was not available if an individual was already near peak levels in the first exercise stage (10 W resistance) or if there was no reported RPE that closely corresponded to one of the calculated intensities (60%, 70%, or 80% Vo2peak). Other measurements
Participants reported demographic variables and medications. Stroke characteristics including date, type, and location were extracted from the medical records. In addition, a number of measures regarding stroke-related deficits were completed. For
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example, stroke-related impairment was assessed using the National Institutes of Health Stroke Scale (NIHSS).17 Functional ability was measured using the Functional Independence Measure (FIM).18 Leg motor impairment was assessed using the ChedokeMcMaster Stroke Assessment (CMSA).19 Expected RPE ranges
Previous research analyzing the relationship between physiologic variables and perceived exertion relied on the 15-point RPE scale. To the best of our knowledge, this is the first report of this nature to use the 10-point RPE scale. The 10-point scale was developed as a simpler category scale with ratio properties.5 It was used because patients with stroke may have an easier time providing a rating of exertion from 1 to 10 as opposed to the more traditional rating on the Borg 15-point RPE scale. Expected RPE ranges for the 10-point RPE scale (CR-10) were generated on the basis of established RPE ranges from the Borg 15-point RPE scale by matching the word anchors for each exercise intensity range.8,20 For example, an RPE range of 11 to 14 on the 15-point RPE scale has been used to represent 60% intensity using maximal HR reserve.8 An RPE rating of 11 on the 15-point scale has a word anchor “fairly light” and matches a rating of 2 on the CR-10, which has the word anchor “weak (light).” An RPE of 14 on the 15-point RPE scale falls between the word anchors “somewhat hard” and “hard” and matches a rating of 4 on the CR-10, which has the word anchor “somewhat strong.”7 Using this technique, we established expected RPE ranges from the CR-10 of 2 to 4 for 60%, 3 to 5 for 70%, and 5 to 7 for 80% of Vo2peak. Statistical analysis
Pa rticipant characteristics were described by mean (SD) or percent (n), as appropriate. Frequency distributions were generated to show the variability of RPE at 60%, 70%, and 80% of Vo2peak. The RPE at each intensity was described by median (interquartile range) and by the proportion of participants falling in the expected RPE range. The proportion of participants falling within versus outside the expected RPE range was compared between intensities using the chi-square test.
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Because considerably fewer participants fell into the expected RPE range at 80% of Vo2peak than at 60% or 70% of Vo2peak in this study and in comparison with healthy participants in a previous study,8 we conducted a secondary analysis to determine whether participant characteristics were associated with the likelihood of reporting within the expected RPE range using chi-square tests or t tests as appropriate. All statistical analyses were conducted using SAS software version 9.1.3 (SAS Institute, Inc., Cary, NC). Results Our study sample (n = 37) had an average age of 65.7 years, was 46.0% female, and completed the exercise test an average of 14.5 days post stroke. See Table 1 for a full account of participant demographics, comorbidities, medications, and stroke characteristics. Mean Vo2peak was 11.3 (±2.5) mL·kg-1·min-1, peak RER was 0.99 (±.09), peak HR was 107.3 (±23.8) bpm, and peak RPE was 6.7 (±2.7). At least 1 of the ACSM criteria for maximal exertion was achieved by 24 of 37 individuals (64.8%), with the majority (18 of 37) achieving an RER ≥1. Among those who did not meet ACSM criteria, the most common reasons for stopping the test early were related to functional impairments including leg effort (6 of 13) and inability to maintain 50 rpm (2 of 13). At 60% and 70% of Vo2peak, more than two-thirds of participants reported an RPE within the expected range (Figure 1). However, fewer than half of the participants reported an RPE within the expected
Table 1. Baseline characteristics of study participants (n = 37) Characteristic
Mean (SD) or n (%)
Age, years Sex (% female) Type of stroke (% ischemic) Stroke hemisphere (% left) Time since stroke, days Medications Beta-blockers (% yes) ACE inhibitors (% yes) Comorbidities Hypertension Dyslipidemia Diabetes Coronary artery disease History of smoking Previous stroke or TIA NIHSS CMSA leg CMSA foot FIM
65.7 (14.3) 17 (46.0%) 27 (75%) 15 (41.7%) 14.5 (10.2) 9 (24.3%) 18 (48.6%) 18 (64.9%) 14 (37.8%) 5 (13.5%) 9 (24.3%) 14 (37.8%) 9 (24.3%) 4.6 (2.4) 4.7 (1.2) 4.0 (1.2) 86.7 (15.8)
Note: ACE = angiotensin-converting enzyme; CMSA = Chedoke-McMaster Stroke Assessment; FIM = Functional Independence Measure; NIHSS = National Institutes of Health Stroke Scale; TIA = transient ischemic attack.
range of 5 to 7 at 80% of Vo2peak (Table 2). In light of this difference, we conducted follow-up analyses to determine whether participant characteristics were associated with the likelihood of falling within versus outside of the expected RPE range at 80% of Vo2peak. However, no differences in participant characteristics were found between subjects who did and those who did not report within the expected RPE range at 80% of Vo2peak (Table 3).
Table 2. Mean RPE and percentage in the expected range at 60%, 70%, and 80% of Vo2peak and corresponding heart rate and workload (median, range) Percent of peak Vo2
Median HR, bpm (range)
Median workload, W (range)
Expected RPE range
Percent reporting (n)a
Median RPE (IQR)
Percent within range (n)
60% 70% 80%
82 (60-112) 86 (52-122) 96 (57-133)
20 (5-30) 20 (10-40) 30 (10-65)
2-4 3-5 5-7
56.8% (21) 78.4% (29) 97.3% (36)
3.0 (3.0–3.5) 3.0 (3.0–5.0) 4.75 (3.0–5.75)
76.2% (16) 69.0% (20) 38.9% (14)*
Note: HR = heart rate; IQR = interquartile range; RPE = rating of perceived exertion; Vo2peak = peak aerobic capacity. a This column indicates the percentage and number of participants that provided an RPE report at the corresponding intensity. Not all participants reported RPE at all 3 intensities, generally because the baseline intensity was above 60% or 70% of their Vo2peak. *P < .05 compared with proportion at 60% of peak Vo2.
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60.0%
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60% Peak VO2
% of Total
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80% Peak VO2
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1
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5 RPE
Figure 1. Histograms displaying percentage of people reporting each RPE at 60%, 70%, and 80% of Vo2peak. Broken lines mark expected RPE range for each intensity. Note that the majority of people fall within the expected range at 60% and 70% of Vo2peak; at 80% of Vo2peak, fewer than half of the people are within the expected range.
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Table 3. Comparisons between subgroups of participants providing RPE values inside or outside the expected range at 80% of peak Vo2 (RPE: 5-7)
Age, years Sex (% female) Heart rate, bpm Work rate, W Type of stroke (% ischemic) Side of stroke (% left) Time since stroke, days ≥1 ACSM criteria for Vo2max (% yes) Peak Vo2, mL/kg/min CMSA leg CMSA foot NIHSS FIM
Within expected RPE range (n=14)
Outside expected RPE range (n=22)
P*
66.1 (10.4) 4 (28.6%) 97.9 (21.4) 34.3 (10.0) 12 (85.7%) 5 (38.5%) 15.2 (15.4) 10 (71.4%) 11.7 (1.9) 4.6 (1.2) 4.0 (1.4) 5.4 (3.0) 88.1 (17.5)
62.8 (16.0) 12 (54.5%) 93.4 (13.8) 25.9 (14.4) 14 (66.7%) 9 (40.9%) 14.0 (5.7) 14 (63.6%) 11.4 (2.7) 4.8 (1.2) 4.0 (1.2) 4.0 (1.9) 86.0 (15.3)
.49 .13 .14 .20 .32 .44 .75 .59 .72 .63 1.00 .13 .72
Note: Values are expressed as mean (SD) or n (%). ACSM = American College of Sports Medicine; CMSA = Chedoke-McMaster Stroke Assessment; FIM = Functional Independence Measure; NIHSS = National Institutes of Health Stroke Scale; RPE = Rating of Perceived Exertion; Vo2max = maximum oxygen consumption. *P < .05 for difference between groups.
Discussion To the best of our knowledge, this is the first study to examine the validity of RPE ranges against a physiological measure of exercise intensity among individuals in the early stage of stroke recovery in inpatient rehabilitation. The majority of participants reported within the expected RPE ranges during moderate-intensity exercise but not during high-intensity exercise. We could not identify any differences in participant characteristics between persons reporting within versus outside the expected RPE range at high intensity. Our data support the view that RPE is appropriate for prescribing and monitoring lowto moderate-intensity exercise among most people after stroke but not for prescribing high-intensity exercise (≥80% Vo2peak). In this study, approximately two-thirds of people in the subacute stage of stroke recovery reported RPE within the expected range at moderate exercise intensities (60% and 70% of Vo2peak), but fewer than 40% reported RPE within the expected range at higher exercise intensities (80% of Vo2peak). These results are
consistent with findings from a prior study of healthy and cardiac populations, 8 in which nearly 70% of patients with cardiac disease reported within expected RPE ranges during moderate-intensity exercise, but fewer than half reported within expected RPE ranges at high intensities. In contrast, the proportion of healthy participants reporting within expected RPE ranges remained above 60% at all exercise intensities.8 Together, these results suggest that RPE in clinical populations may not be a valid indicator of physiological work during higher intensity exercise. That healthy participants are equally likely to report within expected RPE ranges at moderateand high-intensity exercise suggests that health status may affect RPE variability at higher intensities.8,9 One reason for the increased RPE variability among clinical populations could be that fewer participants reach true maximal aerobic capacity. Two-thirds of our population did meet at least one ACSM criteria for maximal Vo2; however, the maximal work rate appeared to be restrained by functional impairments rather than aerobic
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RPE Validity in Subacute Stroke
capacity in our sample, because 25 of 37 (67.6%) tests were stopped because of leg effort or inability to maintain 50 rpm. If RPE is valid for a percentage of maximal Vo2 rather than a percentage of maximal work capacity, then it would be reasonable for RPE to be underreported for people stopping because of functional rather than aerobic reasons. In our sample, half of the participants reported below the expected RPE range at 80% of Vo2peak. It is important to note, however, that presence of functional impairment and failure to meet ACSM criteria did not predict reporting within or outside of the expected RPE range. In contrast to the results of this study, Tang et al10 observed higher RPE values among individuals who were unable to achieve maximal effort on a graded exercise test after stroke, which was in turn related to level of cognition and motor impairment. Individuals with impaired cognitive abilities may have an altered perception of maximal effort during exercise tests and thus may overreport exertion. Nonetheless, these findings suggest that the variability of RPE reports at high intensities after stroke may be due to a complex interaction of several factors that may or may not be related to cardiopulmonary function. A final reason for reporting outside the expected RPE range may be inactivity before the stroke. Stroke and cardiac populations may be more likely to have a history of inactivity relative to healthy populations.21,22 If previously inactive, these populations may not be able to judge their personal physical exertion relative to their maximum capacity. Participants who reported outside the expected RPE range during highintensity exercise had HRs comparable to those of participants who reported within the expected range, even though the majority reported RPE below the expected range. Although the influence of inactivity before the medical event in clinical populations is unclear, inactivity does not influence RPE reporting in healthy populations; active and inactive individuals report similar RPE at ventilatory threshold despite large differences in Vo2.23 Thus, a history of inactivity is not likely to be the main factor leading to variable RPE reporting by patients with stroke but may be one of several factors that together confound perceived exertion in stroke populations.
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Even though our results suggest that RPE ranges are similarly valid for stroke populations and healthy populations at moderate intensities, RPE can be highly variable. Two-thirds of our sample reported within the expected 3-point range, but the range of ratings of perceived exertion was wide at each intensity (Figure 1). Additionally, the median RPE at 60% and 70% Vo2peak were identical. Given these findings, we suggest that RPE and physiological variables (eg,, HR, blood pressure, Vo2) be used in conjunction to monitor exercise intensity when possible. However, exercise monitoring and prescription based solely on RPE at moderate exercise intensity does appear to be sufficient for many people. Study limitations
Eight participants were excluded because the first stage of the maximal exercise test was already >80% Vo2peak. Thus, our results may not be generalizable to the least fit individuals. In addition, 23 participants were missing an RPE for one of the exercise intensities. These missing data generally occurred if the Vo2 during warm-up was greater than 60%, 70%, or 80% of calculated Vo2peak, and, as such, it is possible that sample bias influenced our findings. However, it is worth noting that post hoc analyses that included only people with RPE at all 3 intensities confirmed our results. Thus, the loss of individuals and smaller sample size likely did not alter the findings of this study. However, our moderate sample size may have been too small to detect associations between participant characteristics and RPE reporting. As discussed previously, several participants may not have achieved their true physiologic maximum Vo2, which would influence RPE and the proportion of participants reporting within expected RPE ranges. It is unclear whether the observed relationships between RPE and Vo2 ranges extend to individuals in the chronic stage of stroke recovery. Given that our results are similar to findings in other clinical populations and that participant characteristics were not associated with RPE validity, we anticipate that our findings would be replicated in a chronic stroke population; however, future research is needed to confirm this proposition.
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Conclusions
RPE is frequently used to prescribe exercise intensity in clinical populations in which HR may be variable, such as patients with stroke. However, the validity of RPE ranges among individuals post stroke has not previously been examined. In our study, RPE ranges were valid at moderate exercise intensities and therefore could be considered a practical and valid method for prescribing and monitoring exercise intensity clinically among most patients with stroke. Some clinicians and researchers are now exploring the use of interval training in clinical populations. Among our participants, however, RPE was highly variable during higher intensity exercise, likely because some individuals with stroke-associated functional impairment had difficulty achieving true maximal aerobic capacity. This has important clinical implications; RPE should not be relied on as the sole indicator of physiological exercise intensity at higher intensities among people with stroke.
Future studies should aim to determine whether specific stroke characteristics (eg, functional impairment, cognitive status) influence the validity of RPE reporting. Acknowledgments Conflicts of interest: The authors declare no conflict of interest. Financial support/disclosures: M. Sage is supported by Heart and Stroke Foundation Doctoral Research Award. Dr. Middleton was supported by a Canadian Institute of Health Research fellowship. Dr. Tang is supported by fellowships through the Canadian Institute of Health Research and Michael Smith Foundation for Health Research. Dr. Sibley is supported by a Canadian Institute of Health Research fellowship and the Toronto Rehabilitation Institute. Dr. Brooks holds a Canada Research Chair (Tier 2). Dr. McIlroy holds a University Research Chair.
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