The influence of peripheral afferent signals on the rating of perceived exertion and time to exhaustion during exercise at different intensities

This study determined which peripheral variables would better predict the rating of perceived exertion (RPE) and time to exhaustion (TE) during exercise at different intensities. Ten men performed exercises at first lactate threshold (LT1), second lactate threshold (LT2), 50% of the distance from LT1 to LT2 (TT_50%), and 25% of the distance from LT2 to maximal power output (TW_25%). Lactate, catecholamines, potassium, pH, glucose, V?O₂, VE, HR, respiratory rate (RR) and RPE were measured and plotted against the exercise duration for the slope calculation. Glucose, dopamine, and noradrenaline predicted RPE in TT_50% (88%), LT2 (64%), and TW_25% (77%), but no variable predicted RPE in LT1. RPE (55%), RPE+HR (86%), and RPE+RR (92% and 55%) predicted TE in LT1, TT_50%, LT2, and TW_25%, respectively. At intensities from TT_50% to TW_25%, variables associated with brain activity seem to explain most of the RPE slope, and RPE (+HR and+RR) seems to predict the TE.     

Respiratory and leg muscles perceived exertion during exercise at altitude

We compared the rate of perceived exertion for respiratory (RPE,resp) and leg (RPE,legs) muscles, using a 10-point Borg scale, to their specific power outputs in 10 healthy male subjects during incremental cycle exercise at sea level (SL) and high altitude (HA, 4559 m). Respiratory power output was calculated from breath-by-breath esophageal pressure and chest wall volume changes. At HA ventilation was increased at any leg power output by ～ 54%. However, for any given ventilation, breathing pattern was unchanged in terms of tidal volume, respiratory rate and operational volumes of the different chest wall compartments. RPE,resp scaled uniquely with total respiratory power output, irrespectively of SL or HA, while RPE,legs for any leg power output was exacerbated at HA. With increasing respective power outputs, the rate of change of RPE,resp exponentially decreased, while that of RPE,legs increased. We conclude that RPE,resp uniquely relates to respiratory power output, while RPE,legs varies depending on muscle metabolic conditions.     

Effects of order of presentation of exercise intensities and of sauna baths on perceived exertion during treadmill running

Summary Thirteen male subjects performed a running test on the treadmill consisting of four standard exercise intensities [65%, 75%, 85%, 95% maximal O₂ uptake (VO_2max)] presented in ascending, descending or random order. At the end of each exercise intensity, O₂ consumption, heart rate (f _c), venous blood lactate concentration ([la]_b) and perceived exertion were assessed. This last variable was determined according to the Borg nonlinear CR-20 scale. The same variables were also determined during exercise at a standard intensity (65% or 95%VO_2max) performed before and after a Finnish sauna bath. Ratings of perceived exertion showed a good test-retest reliability (r=0.77); they were the same when the exercise intensity was expressed in relative (%VO_2max) or absolute (speed) terms, and were independent of the order of presentation of the exercise. The latter had no effect onf _c either but it did, however, influence [la]_b, which was significantly higher in the descending, as compared to the ascending or random modes of presentation. The sauna bath increasedf _c at a given exercise intensity, but left perceived exertion and [la]_b unchanged. It was concluded that at least under the present experimental conditions,f _c and venous [la]_b do not play a major role as determinants of perceived exertion.     

Rating of perceived exertion during two different constant-load exercise intensities during arm cranking in paraplegic and able-bodied participants

This study assessed the relationship between rating of perceived exertion (RPE) and time to exhaustion during arm cranking exercise while exercising at two different constant-load exercise intensities in able-bodied and paraplegic individuals. The second aim of this study was to assess the rate of change in the RPE between the two different constant-load exercise intensities in absolute and relative terms. Ten able-bodied men and ten paraplegic men performed four exercise tests: (1) a ramp exercise test (started at 0 W and increased by 15 W min⁻¹), (2) a graded exercise test (GXT) (started at 30 W and increased by 15 W every 2 min); these tests were performed in counterbalanced order, (3) a constant-load exercise test equal to 50% delta [i.e., the difference between the gas exchange threshold and peak power output (Δ)], (4) a constant-load exercise test equal to 70% Δ; these tests were also performed in counterbalanced order. There was a strong linear relationship between the RPE and time to exhaustion (R ² ≥ 0.88) irrespective of exercise intensity and participants’ group. As expected, the rate of change in the RPE was significantly greater during 70% Δ compared to 50% Δ when the RPE was regressed against absolute time regardless of group. However, differences in the rate of change in the RPE were removed when the RPE was regressed against proportion of time, irrespective of group. These findings have important implications for predicting time to exhaustion while exercising at constant-load exercise intensity during arm cranking in able-bodied and paraplegic individuals.     

Effect of air ionization on heart rate and perceived exertion during a bicycle exercise test

Summary The influence of ionization of air on heart rate (HR) and ratings of perceived exertion (RPE) during bicycle exercise was studied in nine healthy medical students selected according to a randomized schedule from the class of 90 students. The exercise tests were performed both under negative and positive ionization. The study was made with a double-blind, cross-over design. The body surface exposed to ionic current was made large by reducing the clothing of the subject. A significant overall tendency to lower HR and RPE values under negative ionization was observed (p<0.01, sign test). The RPE values were significantly lower (p<0.01, paired t-test and the Wilcoxon test) under negative than under positive ionization at the maximal work load level but not at other relative load levels. However, when separately tested at each relative load level HR values did not differ significantly in negative and positive ionization.The results of this pilot study indicate that ionic composition of the air can modify the RPE and possibly also HR during exercise; negative air ionization seems to be beneficial compared with positive ionization. The mechanisms involved are obscure, but we suggest that negative ionization of air may increase oxidative metabolism through generation of a superoxide radical (O₂ ^–) that is reduced to H₂O₂ by superoxide dismutases.     

The effects of different inspiratory muscle training intensities on exercising heart rate and perceived exertion

This study investigated the relationship between the intensity of an inspiratory muscle training programme and its effect on respiratory muscle strength, exercising heart rate, and ratings of perceived exertion. A total of 66 subjects were randomly assigned to one of three groups. One group trained at 100% of maximum inspiratory pressure (MIP) for 6 weeks (MAX, n=22). A second group performed 6 weeks of inspiratory muscle training at 80% of MIP (SUB, n=21) and a third control group received no inspiratory training (CON, n=23). Both the MAX and SUB training groups improved MIP relative to the control group [32 (19) cmH₂O, P=0.01; 37 (25) cmH₂O, P=0.001, respectively]. A significant decrease in heart rate [–6 (9) beats min^–1, P=0.02] and rating of perceived exertion [–0.5 (1.4), P=0.04] was observed for the MAX group only. It is concluded that 6 weeks of both MAX and SUB training were sufficient to improve inspiratory muscle strength. However, exercising heart rate and perceived exertion decreased with MAX training only.     

Prediction of maximal oxygen uptake from submaximal ratings of perceived exertion and heart rate during a continuous exercise test: the efficacy of RPE 13

This study assessed the utility of a single, continuous exercise protocol in facilitating accurate estimates of maximal oxygen uptake ( [(V)\dot] \textO ₂ \dot{V} {\text{O}}_{ 2} max) from submaximal heart rate (HR) and the ratings of perceived exertion (RPE) in healthy, low-fit women, during cycle ergometry. Eleven women estimated their RPE during a continuous test (1 W 4 s⁻¹) to volitional exhaustion (measured [(V)\dot] \textO ₂ \dot{V} {\text{O}}_{ 2} max). Individual gaseous exchange thresholds (GETs) were determined retrospectively. The RPE and HR values prior to and including an RPE 13 and GET were extrapolated against corresponding oxygen uptake to a theoretical maximal RPE (20) and peak RPE (19), and age-predicted HRmax, respectively, to predict [(V)\dot] \textO ₂ \dot{V} {\text{O}}_{ 2} max. There were no significant differences (P > 0.05) between measured (30.9 ± 6.5 ml kg⁻¹ min⁻¹) and predicted [(V)\dot] \textO ₂ \dot{V} {\text{O}}_{ 2} max from all six methods. Limits of agreement were narrowest and intraclass correlations were highest for predictions of [(V)\dot] \textO ₂ \dot{V} {\text{O}}_{ 2} max from an RPE 13 to peak RPE (19). Prediction of [(V)\dot] \textO ₂ \dot{V} {\text{O}}_{ 2} max from a regression equation using submaximal HR and work rate at an RPE 13 was also not significantly different to actual [(V)\dot] \textO ₂ \dot{V} {\text{O}}_{ 2} max (R ²  = 0.78, SEE = 3.42 ml kg⁻¹ min⁻¹, P > 0.05). Accurate predictions of [(V)\dot] \textO ₂ \dot{V} {\text{O}}_{ 2} max may be obtained from a single, continuous, estimation exercise test to a moderate intensity (RPE 13) in low-fit women, particularly when extrapolated to peak terminal RPE (RPE₁₉). The RPE is a valuable tool that can be easily employed as an adjunct to HR, and provides supplementary clinical information that is superior to using HR alone.     

Differentiated ratings of perceived exertion at ventilatory threshold in children and adults

The purpose of this study was to examine overall, leg and chest ratings of perceived exertion (RPE) at ventilatory threshold (Th_vent) in 16 children (mean age 10.9 years) and 17 adults (mean age 24.3 years). Th_vent and maximum oxygen consumption (V˙O_{2 max} ) were measured during a graded exercise test on a cycle ergometer. Overall, leg and chest RPE were obtained at the end of each exercise stage. V˙O_{2 max} was 49.9 (8.5) and 47.1 (6.1) ml · kg^?1· min^?1 [mean (SD)] in the adults and children, respectively (P > 0.05). Relative to V˙O_{2 max} , Th_vent was 61.7 (5.3)% in the adults and 64.7 (5.2)% in the children (P > 0.05). Overall, leg, and chest RPE values at Th_vent for the adults were 11.5 (2.6), 11.9 (2.5), and 10.5 (2.5), while for the children these values were 13.6 (2.2), 14.1 (2.2), and 12.6 (2.3), respectively. All RPE values were higher for the children (P < 0.05). These results suggest that children are able to discriminate levels of exertion in different parts of their body during graded exercise. Furthermore, children rate an intensity corresponding to Th_vent to require a greater overall, leg and chest effort than adults exercising at a similar intensity. This indicates that children experience more pronounced cardiorespiratory and muscular sensations during this type of exercise.     

Similarity in physiological and perceived exertion responses to exercise at continuous and intermittent critical power

The purpose of this study was to compare the physiological responses [oxygen uptake (VO₂), heart rate (HR) and blood lactate concentrations ([BLa])] and the rating of perceived exertion (RPE) response until exhaustion (TTE) at the continuous (CP_c) and intermittent (CP_i) critical power workloads. Ten moderately active men (25.5 ± 4.2 years, 74.1 ± 8.0 kg, 177.6 ± 4.9 cm) participated in this study. The incremental test was applied to determine the highest values of oxygen uptake (VO_2max), heart rate (HR_max), blood lactate concentrations ([BLa_max]), and maximal aerobic power (MAP). Continuous and intermittent exhaustive predictive trials were performed randomly. The hyperbolic relation between power and time was used to estimate CP_c and CP_i. CP_i was derived from predictive trial results at an effort and recovery ratio of 30:30 s. Exercise at CP_c and CP_i as well as the physiological and RPE responses were measured until exhaustion. The values of physiological variables during CP_c and CP_i did not differ in either TTE test and were lower than the VO_2max, HR_max and [BLa_max] values. RPE was maximal at the end of exercise at CP_c and CP_i. There was a high correlation between VO_2max (L min⁻¹) and CP_c and CP_i intensities (r ≥ 0.90) and between MAP, CP_c and CP_i (r ≥ 0.95). Similar physiological and RPE responses were found at CP_c and CP_i for the times analyzed.     

Regulating intensity using perceived exertion: effect of exercise duration

To examine whether the validity of perception-based intensity regulation would be affected by exercise duration, 20 subjects were recruited to complete a maximal exercise test (GXT) and four submaximal trials of varying duration and intensity using a cyle ergometer. During GXT, ratings of perceived exertion (RPE), oxygen uptake (VO₂), heart rate (HR), and power output (PO) equivalent to 50 and 75% VO_2peak were determined. During each trial, subjects were to produce and maintain a workload using RPE estimated at 50 or 75% VO_2peak for 20 or 40 min, and VO₂, HR, and PO were measured throughout the exercise. No differences in average VO₂ were found between the estimation and production trial of either duration. However, average HR and PO were lower (P < 0.05) during the production trial of both durations. It appears that exercise duration has a minimal impact upon the accuracy of using RPE to regulate a target metabolic demand.     

The use of ratings of perceived exertion for regulating exercise levels in rowing ergometry

The purpose of this study was to examine the validity of the use of ratings of perceived exertion (RPE) to estimate and regulate exercise intensity during rowing ergometry. Nine competitive male rowers [mean age 28.6 years, (SD 6.3)] completed two rowing trials on an ergometer. The first trial (estimation) consisted of an incremental protocol designed to elicit a range of work outputs (WO) and heart rates (HR). The subjects indicated their perception of effort using a 15-point scale at each intensity level. In the second trial (production), 7–14 days later, the subjects were asked to produce exercise intensities corresponding to five levels of RPE: 15,11,17,13, and 19. Data analysis revealed high Pearson correlation coefficients between HR and RPE (r = 0.95,P < 0.01) and WO and RPE (r = 0.96,P < 0.01) during the estimation trial. In addition, significant correlations (P < 0.01) were obtained between the estimation and production trials for HR (r = 0.82) and WO (r = 0.84). Posthoc analysis of variance revealed that the observed differences in mean HR were not significant (P > 0.05) at three of the five intensity levels (RPE 15,17 and 19), but were at the two lowest RPE levels (11 and 13). Significant mean differences in WO were seen at all but RPE 17. These data support the validity of the RPE scale as a measure of physiological strain among competitive male rowers, and offer support for its use as a method of regulating the intensity of rowing ergometry, especially at higher levels.     

The effect of passive heating and face cooling on perceived exertion during exercise in the heat

Increased body temperature is thought to be an important component of the higher perception of exertion that is a feature of fatigue during exercise in the heat but a causal relationship has yet to be demonstrated. We have investigated the effect of passive heating on the perception of exertion during a standard bout of exercise and also assessed the effect of cooling the head on compensating for the increased body temperature on the feelings of exertion. Ten male subjects performed a 14-min cycling exercise [average power ~63% of maximum power output ( _max)] at an ambient temperature of 35°C at resting rectal temperature [mean (SD): 37.49 (0.27)°C; control (CON) trial] on one occasion, and after sitting in a sauna to raise rectal temperature [mean (SD): 38.95(0.13)°C; sauna (SAU) trial]. During the exercise, subjects reported their ratings of overall perceived exertion (RPE), perceived exertion of the legs (RPE_legs) and thermal comfort (TC). A blood sample was collected by the end of the exercise for determination of plasma glucose, lactate and prolactin and haematocrit. RPE values were significantly elevated after passive heating [mean (SE): 14.5 (0.7) units in CON and 17.2 (0.5) units in SAU, at the end of exercise; P<0.001] as were the RPE_legs (P<0.01), while ratings of TC were similar in CON and SAU trials. Passive heating increased blood glucose (P<0.05) but had no effect on lactate at the end of the exercise. Plasma prolactin was markedly elevated as a result of the sauna exposure [mean (SE): 1598 (152) versus 225 (31) mU l^–1 in SAU and CON trials, respectively; P<0.001]. Six of the subjects repeated the two trials but with the face cooled during exercise (trials CON_FAN and SAU_FAN) that was achieved by combining face fanning and spraying the face with a mist of cooled water. Face cooling decreased RPE values after sauna to a point that no differences between the two conditions existed. RPE_legs scores and heart rate, however, remained higher in SAU_FAN compared with CON_FAN (P<0.05). We conclude that hyperthermia is a causative element of the increased perception of exertion during submaximal exercise in the heat and that the effect of increased core temperature on the feelings of exertion is modulated by face cooling.     

The effects of voluntary contraction intensity and gender on perceived exertion during isokinetic quadriceps exercise

The objectives of the present study were to: (1) examine perceived exertion across different target voluntary contraction intensities, (2) compare perceived exertion ratings with actual target intensities, and (3) compare perceived exertion ratings between males and females. The subjects for this study included 30 healthy, college-aged male (n=15) and female (n=15) volunteers. All subjects were free of orthopedic, cardiopulmonary, systemic and neurological disease. Each subject completed five maximal isokinetic, concentric quadriceps contractions in a seated position at 60° · s⁻¹ to determine their single, highest peak torque. All subjects then completed, in a random order, 3–5 submaximal isokinetic contractions at 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90% of their single, highest peak torque. Each relative contraction level (i.e., percentage) was achieved by having the subjects attempt to match the peak of their torque curve to a horizontal line on a computer monitor. Perceived exertion was measured by asking the subjects to provide a number that corresponded to the feelings in their quadriceps during exercise by viewing a modified category-ratio (CR-10) scale. The results of a two-factor (gender × intensity) analysis of variance revealed a significant, intensity main effect (F _8,232=92.19, P < 0.001, η²=0.77, 1–β=0.99) and no significant gender main effect (F _8,232=2.66, P = 0.11, η²=0.09, 1–β=0.35) or interactions (F _8,232 = 1.01, P=0.43, η²=0.04, 1–β=0.46). The findings of this study demonstrate that perceived exertion is significantly (P < 0.05) different from the specific target values on the CR-10 scale at 10%, and 50–90% maximum voluntary contraction. The results revealed that the increase in perceived exertion across the contraction intensities could be fit to both linear (F _1,29=205.41, P < 0.001, η²=0.88, 1–β=0.99) and quadratic (F _1,29=10.05, P=0.004, η²=0.26, 1–β=0.87) trends. These findings suggest that perceived exertion is underestimated during submaximal isokinetic exercise, and is not different between males and females. Accepted: 18 October 2000     

The rate of heat storage mediates an anticipatory reduction in exercise intensity during cycling at a fixed rating of perceived exertion

The aim of the present study was to examine the regulation of exercise intensity in hot environments when exercise is performed at a predetermined, fixed subjective rating of perceived exertion (RPE). Eight cyclists performed cycling trials at 15°C (COOL), 25°C (NORM) and 35°C (HOT) (65% humidity throughout), during which they were instructed to cycle at a Borg rating of perceived exertion (RPE) of 16, increasing or decreasing their power output in order to maintain this RPE. Power output declined linearly in all three trials and the rate of decline was significantly higher in HOT than in NORM and COOL (2.35 ± 0.73 W min⁻¹, 1.63 ± 0.70 and 1.61 ± 0.80 W min⁻¹, respectively, P < 0.05). The rate of heat storage was significantly higher in HOT for the first 4 min of the trials only, as a result of increasing skin temperatures. Thereafter, no differences in heat storage were found between conditions. We conclude that the regulation of exercise intensity is controlled by an initial afferent feedback regarding the rate of heat storage, which is used to regulate exercise intensity and hence the rate of heat storage for the remainder of the anticipated exercise bout. This regulation maintains thermal homeostasis by reducing the exercise work rate and utilizing the subjective RPE specifically to ensure that excessive heat accumulation does not occur and cellular catastrophe is avoided.     

Prediction of peak oxygen uptake from sub-maximal ratings of perceived exertion elicited during a graded exercise test in obese women

The purpose was to assess the validity of predicting peak oxygen uptake     from Ratings of Perceived Exertion (RPE)≤15, during a graded exercise test (GXT), in obese women. Forty-three obese women performed GXT to volitional exhaustion. During GXT, oxygen uptake     and RPE were measured. Individual linear regressions between     and RPE≤15 were extrapolated to RPE 20 in order to predict     . Actual and predicted     were not significantly different (13.9±3.0 vs 14.2±3.3 ml kg⁻¹ min⁻¹, respectively; p =.26). The Pearson product moment correlation between actual and predicted     was high ( r =0.82). The 95% limits of agreement analysis on these values (bias±1.96SD) was −0.3±3.7 ml kg⁻¹ min⁻¹. Results suggested that RPE≤15 elicited during a sub-maximal GXT provides accurate     prediction. Therefore, it is not necessary to perform GXT to voluntary exhaustion to determine     in obese women.     

Blood glucose extraction as a mediator of perceived exertion during prolonged exercise

Summary The effect of blood glucose extraction on the perception of exertion was examined during prolonged arm exercise. Eight male subjects consumed in counterbalanced order a standard daily diet containing either (1) 75 g dihydroxyacetone and 25 g sodium pyruvate (DHAP) or (2) an isocaloric amount of placebo, to manipulate blood glucose extraction. Following each 7-day diet, subjects exercised to exhaustion at 60% of peak arm oxygen consumption. Ratings of perceived exertion (Borg, CR-10 scale) were obtained for the arms (RPE-A), legs (RPE-L), chest (RPE-C) and overall body (RPE-O) every 10 min of exercise. After 60 min of continuous exercise, blood samples were drawn from the radial artery and axillary vein. Ratings of perceived exertion did not differ between trials during the first 50 min of exercise. At the 60-min time point, perceived exertion was lower (P < 0.01) in the DHAP than placebo trials for the arms (RPE-A: 4.25 vs 5.50) and overall body (RPE-O: 3.25 vs 4.00). These differences persisted throughout exercise. RPE-L and RPE-C did not differ between trials. Whole-arm arterial-venous glucose difference was higher (P < 0.05) in the DHAP (1.00 mmol · 1^–1) than placebo (0.36 mmol·1^–1) trials, as was fractional extraction of glucose (22.5 vs 9.0%). Respiratory exchange ratio was the same between trials. Triceps muscle glycogen was (1) higher in the DHAP than placebo trial at pre-exercise (P < 0.05), (2) decreased during exercise and (3) did not differ between trials at exercise termination. Free fatty acids, glycerol, -hydroxybutyrate, lactic acid, pH, norepinephrine and epinephrine did not differ between trials. These findings suggest that blood glucose extraction mediates the perceived intensity of exertion arising from active limbs during prolonged arm exercise.     

The effects of specificity of training on rating of perceived exertion at the lactate threshold

Summary To determine the effects of cycle and run training on rating of perceived exertion at the lactate threshold (LT), college men completed a 40-session training program in 10 weeks (n=6 run training,n=5 cycle training,n=5 controls). Pre-and post-training variables were measured during graded exercise tests on both the bicycle ergometer and treadmill. ANOVA on the pre- and post-training difference scores resulted in similar improvements in for both testing protocols, regardless of training mode. The run training group increased at the LT by 58.5% on the treadmill protocol and by 20.3% on the cycle ergometer. Cycle trainers increased LT only during cycle ergometry (+38.7%). No changes were observed in the control group. No differences for RPE at the LT were found before or after training, or between testing protocols for any group. Perception of exercise intensity at the LT ranged from “very light” to “light”. The relationship between RPE and was altered by the specific mode of training, with trained subjects having a lower RPE at a given (no change in RPE at max.). It was concluded that RPE at the LT was not affected by training, despite the fact that after training the LT occurs at a higher work rate and was associated with higher absolute and relative metabolic and cardiorespiratory demands.     

Effects of blood glucose concentration on ratings of perceived exertion during prolonged low-intensity physical exercise

The purpose of this investigation was to determine the relationship between blood glucose concentration and perceived exertion during prolonged low-intensity exercise. After a 12-h overnight fast, seven young healthy males began bicycle exercise from 0800 h at 50% Vo2max. One hour after initiation of the exercise, 20% glucose was infused by means of an infusion pump, to maintain blood glucose concentration at a level of approximately 6.5 mM for 20 min. This was followed by 20 min of sham infusion (no glucose). This 40-min cycle was repeated until 220 min of exercise. During the first 120 min of exercise, the ratings of perceived exertion (RPE) increased gradually without any effects of the glucose infusion. Thereafter, RPE tended to decrease during glucose infusion, and finally showed a significant decrease from 180 (17 +/- 2) to 190 (16 +/- 2) min. This result showed that an increase in blood glucose concentration has a significant effect on perceived exertion, even if exercise time is prolonged. The different responses of RPE during the two phases of the exercise may be explained by the difference of glycogen concentration in muscle, because glucose infusion had no effect on RPE when muscle glycogen content was presumed to be at normal level, and was effective when glycogen in the exercising muscles was presumed to be depleted.