The validity of regulating blood lactate concentration during running by ratings of perceived exertion

Comparison of Borg- and OMNI-RPE as Markers of the Blood Lactate Response to Exercise

PURPOSE

To examine the utility of the Borg (6-20) and adult OMNI walk/run (0-10) ratings of perceived exertion (RPE) scales as markers of the blood lactate response to exercise.

METHODS

Thirty-six (26 females and 10 males) individuals with the metabolic syndrome (mean+/-SEM: age, 45.8+/-2.0 yr; height, 168.4+/-1.3 cm; weight, 100.4+/-3.6 kg) completed a continuous peak oxygen uptake (VO2peak)/lactate threshold (LT) treadmill protocol. VO2 (mL.kg.min), blood lactate concentration (BLC, mM), and heart rate (bpm) were measured at the end of each stage. RPE were assessed at 2:15 and 2:45 of each 3-min stage using both RPE scales presented in a counterbalanced order. Participants were read standardized instructions specific to each scale. The LT and BLC of 2.5 and 4.0 mM were determined from the blood lactate-velocity relationship.

RESULTS

The mean Borg, OMNI, and standardized (to the Borg scale) OMNI-RPE values at the LT and BLC of 2.5 mM, 4.0 mM, and peak ranged from 10.1 to 16.9, 3.1 to 8.2, and 9.9 to 17.1, respectively. No differences were observed between Borg and standardized OMNI-RPE at any exercise intensity. The correlation within and between Borg- and OMNI-RPE and the velocities associated with LT, BLC of 2.5 mM, 4.0 mM, and peak ranged from r=0.82 to 0.93 (P<0.01). Mean differences (95% CI) between the Borg- and standardized OMNI-RPE at LT, and BLC of 2.5 mM, 4.0 mM, and peak were 0.27 (-2.26, 2.80), -0.48 (-3.14, 2.18), -0.29 (-2.92, 2.35), and 0.10 (-1.65, 1.84), respectively.

CONCLUSION

Both the Borg and OMNI walk/run scales demonstrate predictive utility as markers of the blood lactate response to incremental exercise in individuals with the metabolic syndrome.

RPE Association with Lactate and Heart Rate during High-Intensity Interval Cycling

PURPOSE

Physiological and perceptual measures during interval exercise are not well understood. The current study therefore examined the correspondence between RPE, HR, and blood lactate concentration ([La]) during interval cycling.

METHODS

VO2peak and the 4.0 mmol x L(-1) lactate threshold were determined. In session 2, subjects (N = 12) warmed up (10 min, 0 W) and completed five 2-min intervals (INT) at >4 mmol x L(-1) workload, each separated by 3 min of recovery (REC) (60 rpm, 0 W). HR, RPE, and [La] were recorded at 10 min, at the conclusion of each INT, and each REC and 5- and 10-min recovery.

RESULTS

Repeated-measures ANOVA showed [La], HR, and RPE increased significantly across time (INT and REC). At each time point, repeated-measures ANOVA was used to compare standardized data (alpha = 0.05). RPE (at INT) intensified concurrently with HR and [La] at INT. Correlations were significant for INT (P < or = 0.05) (HR-RPE: r = 0.63, [La]-RPE: r = 0.43). Similarly, RPE and HR for REC systematically increased with [La]. Correlations for REC were also significant (HR-RPE: r = 0.44, [La]-RPE: r = 0.34). Correlations were also significant for INT and REC combined (HR-RPE: r = 0.70, [La]-RPE: r = 0.22).

CONCLUSIONS

INT and REC independently showed moderate correspondence for RPE-[La] and RPE-HR. However, tighter overall coupling of HR with RPE (vs [La] with RPE) and a dissociation between RPE-[La] suggest RPE during intervals of intense cycling were more sensitive to acute metabolic demand (evidenced by HR) versus [La].

Metabolic and perceptual responses during Spinning cycle exercise

PURPOSE

The present investigation was undertaken to compare metabolic and perceptual responses between exercise performed at constant intensity (CON) and with a Spinning protocol of variable intensity (VAR).

METHOD

Fifteen subjects, including seven males and eight females (23 +/- 5 yr, 72 +/- 17 kg, and 171 +/- 10 cm), underwent two experimental trials. During each trial, subjects performed a 30-min cycle exercise protocol that was followed by a 30-min recovery period. Exercise was performed at 67 +/- 3% (means +/- SD) of HR(max) in CON. In VAR, the similar intensity (68 +/- 4% HR(max)) was also achieved, although the protocol entailed alternating phases of both higher and lower intensity arranged similarly to what is designed for a typical Spinning workout. Oxygen uptake (VO2) and HR were measured at rest and throughout both exercise and recovery, whereas RPE were recorded during exercise only. Plasma lactate concentrations [La] were determined at rest, the end of exercise, and the end of recovery.

RESULTS

No differences in average VO2, HR, and RPE were found during exercise between CON and VAR. However, average VO2 and HR were higher (P < 0.05) in VAR than CON (0.33 +/- 0.03 vs 0.26 +/- 0.02 L x min(-1) and 91 +/- 3 vs 80 +/- 2 beats x min(-1), respectively). [La] was higher (P < 0.05) at the end of exercise in VAR than CON (7.2 +/- 0.8 vs 2.7 +/- 0.3 mmol x L(-1)), but became similar at the end of recovery.

CONCLUSION

An exercise regimen in which intensity varies exerts no added effect on metabolic and perceptual responses during exercise as long as the average intensity is kept the same. However, VAR resulted in a greater [latin capital V with dot above]O2 after exercise, and this augmented postexercise oxygen consumption may be mediated in part by elevated plasma [La].

[Determination of ventilatory threshold based on subjective rating of perceived exertion]

The objective of the study was to test the possibility of using the fixed value (12-13) of the Rating of Perceived scale (RPE scale), as a valid method for determination of ventilatory threshold (VT). The sample of the subjects included 32 physically active males (age: 22.3; TV: 180.5; TM: 75.5 kg; VO2max: 57.1 mL/kg/min). During the continuous test of progressively increasing load on a treadmill, cardiorespiratory and other parameters were monitored using ECG and gas analyzer. Following the test, VT and VO2max were determined. During the test, at each level, at the scale from 6 to 20, the subjects pointed the number that suited best their currently feeling of strain. The RPE threshold was defined as constant value of 12-13. Average values of ventilatory and RPE threshold were expressed by parameters that were monitored and then compared by using t-test for dependent samples. No significant difference was found between mean values of VT and RPE threshold, when they were expressed by relevant parameters: speed, load, heart rate, absolute and relative oxygen consumption. Fixed value (12-13) of RPE scale may be used to detect the exercise intensity that corresponds to ventilatory threshold.

RPE-lactate dissociation during extended cycling

This study examined the association of blood lactate concentration [La] and heart rate (HR) with ratings of perceived exertion (RPE) during 60 min of steady workload cycling. Physically active college-aged subjects (n = 14) completed an exhaustive cycling test to determine VO(2) (peak) and lactate threshold (2.5 mmol l(-1)). Subjects then cycled for 60 min at the power output associated with 2.5 mmol l(-1) [LA]. HR, [LA], RPE-overall, RPE-legs and RPE-chest were recorded at 5, 10, 20, 30, 40, 50 and 60 min. The 60-min trials were below maximal lactate steady state, with peak lactate concentration occurring at 20 min after which [LA] declined. The 20-min point was therefore considered pivotal, and data at other points were compared to this time point. Repeated measures ANOVA with simple contrasts (alpha = 0.05) showed (a) [LA] at 40, 50 and 60 min was significantly lower than at 20 min, (b) RPE-O and RPE-L were significantly greater at 30, 40, 50 and 60 min than at 20 min, (c) RPE-C was significantly greater at 40, 50 and 60 min than at 20 min, and (d) HR was significantly greater at 30, 40, 50 and 60 min than at 20 min. Significant (P < 0.05) positive correlations were found between HR and RPE-O (r = 0.43), RPE-L (r = 0.48) and RPE-C (r = 0.41) while correlations for [LA]-HR (r = 0.13) and [LA]-RPE (RPE-O: r = -0.11, RPE-L: r = 0.01, RPE-C: r = -0.06) were weak and non-significant. There is a dissociation of RPE and [LA] owing to RPE drift and lactate kinetics in longer duration sub-maximal exercise. Apparently, [LA] is not a strong RPE mediator during extended cycling.

Utilização do esforço percebido na determinação da velocidade crítica em corrida aquática

A relação linear entre intensidade do exercício e taxa de aumento da atividade neuromuscular avaliada pela eletromiografia permite a estimativa do limiar de fadiga, que seria a intensidade que poderia ser mantida indefinidamente sem aumento dos sinais eletromiográficos ao longo do tempo. Levantou-se a hipótese de que a percepção subjetiva de esforço teria comportamento semelhante ao da ativação neuromuscular e que um limiar de esforço percebido (LEP), identificado de forma semelhante ao limiar de fadiga eletromiográfica, poderia coincidir com a velocidade crítica (VCrit). Treze indivíduos de ambos os sexos (23,0 ± 2,5 anos), em uma piscina de 15m de extensão e 2,5m de profundidade, realizaram três testes exaustivos de corrida aquática para determinação dos parâmetros do modelo de velocidade crítica, reportando o esforço percebido (escala de Borg de 6-20 pontos), a cada 15m. Para identificação do LEP, os coeficientes de inclinação das retas do aumento do esforço percebido no tempo (ordenada) e velocidades utilizadas (abscissa) foram ajustados a uma função linear que fornecia um ponto no eixo da velocidade onde, teoricamente, o esforço percebido seria estável indefinidamente. A VCrit foi estimada pelas equações usadas no modelo de velocidade crítica. Para comparação das estimativas de VCrit e do LEP, e de suas associações, foi feita ANOVA para medidas repetidas (p < 0,05) e calculada a correlação de Pearson. Os dados obtidos para a determinação da VCrit atenderam aos critérios adotados para a validade do modelo; a VCrit e o LEP não apresentaram diferença estatística (0,23 ± 0,02m/s x 0,24 ± 0,03m/s) e foram significativamente correlacionados (r = 0,85). Esses resultados sugerem que o LEP parece representar a intensidade máxima de exercício em que variáveis fisiológicas e psicofísicas encontrariam estabilidade, e que esse índice pode ser utilizado na determinação da VCrit.

Cerebral perturbations provoked by prolonged exercise

This review addresses cerebral metabolic and neurohumoral alterations during prolonged exercise in humans with special focus on associations with fatigue. Global energy turnover in the brain is unaltered by the transition from rest to moderately intense exercise, apparently because exercise-induced activation of some brain regions including cortical motor areas is compensated for by reduced activity in other regions of the brain. However, strenuous exercise is associated with cerebral metabolic and neurohumoral alterations that may relate to central fatigue. Fatigue should be acknowledged as a complex phenomenon influenced by both peripheral and central factors. However, failure to drive the motorneurons adequately as a consequence of neurophysiological alterations seems to play a dominant role under some circumstances. During exercise with hyperthermia excessive accumulation of heat in the brain due to impeded heat removal by the cerebral circulation may elevate the brain temperature to >40 degrees C and impair the ability to sustain maximal motor activation. Also, when prolonged exercise results in hypoglycaemia, perceived exertion increases at the same time as the cerebral glucose uptake becomes low, and centrally mediated fatigue appears to arise as the cerebral energy turnover becomes restricted by the availability of substrates for the brain. Changes in serotonergic activity, inhibitory feed-back from the exercising muscles, elevated ammonia levels, and alterations in regional dopaminergic activity may also contribute to the impaired voluntary activation of the motorneurons after prolonged and strenuous exercise. Furthermore, central fatigue may involve depletion of cerebral glycogen stores, as signified by the observation that following exhaustive exercise the cerebral glucose uptake increases out of proportion to that of oxygen. In summary, prolonged exercise may induce homeostatic disturbances within the central nervous system (CNS) that subsequently attenuates motor activation. Therefore, strenuous exercise is a challenge not only to the cardiorespiratory and locomotive systems but also to the brain.

Regulating Oxygen Uptake during High-Intensity Exercise Using Heart Rate and Rating of Perceived Exertion

PURPOSE

The purpose of this study was to comparatively evaluate the use of heart rate (HR) or rating of perceived exertion (RPE) in eliminating the slow component of oxygen uptake (.VO2) during high-intensity aerobic exercise.

METHODS

Nine sedentary males (age = 23.9 +/- 4.6 yr, height = 177.4 +/- 10.1 cm, weight = 75.28 +/- 12.95 kg) completed three 15-min submaximal exercise cycle ergometer tests based on: 1) constant power output (PO) corresponding to 75% .VO2max (PO75), 2) HR corresponding with 75% .VO2max (HR75), and 3) RPE response corresponding with 75% .VO2max (RPE75). .VO2, HR, RPE, and blood lactate concentration [La-] were measured during all tests. Data were analyzed using repeated measures analysis of variance, and post hoc means comparisons were performed using a Fisher's LSD test.

RESULTS

End-exercise .VO2 was significantly higher than the respective 3-min .VO2 for the PO75 and RPE75 tests, but not the HR75 test. End-exercise .VO2 was significantly greater for the PO75 test than both the RPE75 and HR75 tests, but there was no significant difference between end-exercise .VO2 for the RPE75 and HR75 tests. End-exercise HR and RPE were significantly higher for the PO75 test than both the RPE75 and HR75 tests. There were no significant differences between the RPE75 and HR75 tests for end-exercise HR or end-exercise RPE.

CONCLUSION

Results suggest using both HR and RPE are effective at reducing the slow component of .VO2 that occurs during high-intensity exercise.

Blood lactate recovery and perceived readiness to start a new run in middle-distance runners during interval training

The aim of this study was to establish to what extent ratings of perceived readiness to start a new run are dependent on recovery of blood lactate and heart rate during passive recovery between interval runs (4 x 2000 m) of increasing intensity by 15 male college-level middle-distance runners. The Perceived Readiness Rating scale was administered at each minute of recovery. Blood lactate concentration was measured immediately after runs at Min. 3 of recovery after the first and second runs, and, in addition, at Min. 6 of recovery after the third and fourth runs. Heart rate was recorded continuously during the runs and during recovery. The obtained correlation between blood lactate recovery and perceived readiness ratings after the third and fourth runs were -.36 and -.56, respectively (p<.05). Consequently, blood lactate concentration recovery appears to influence the middle-distance runners' perceived readiness estimation to begin a new run. The Perceived Readiness Rating applied by us appears useful in the training of middle-distance runners.

Relationships between recall of perceived exertion and blood lactate concentration in a judo competition

Relationships between perceived exertion and blood lactate have usually been studied in laboratory or training contexts but not in competition, the most important setting in which sports performance is evaluated. The purpose of this study was to examine the relationships between psychological and physiological indices of the physical effort in a competition setting, taking into account the duration of effort. For this, we employed two Ratings of Perceived Exertion (RPE and CR-10) and lactic acid plasma concentration as a biological marker of the effort performed. 13 male judo fighters who participated in a sports club competition provided capillary blood samples to assay lactate concentrations and indicated on scale their Recall of Perceived Exertion in the total competition and again in just the Last Fight to compare the usefulness of RPE and CR-10 in assessing discrete bouts of effort and a whole session. Analysis showed that perceived exertion or the effort made during the whole competition was positively and significantly related to maximal lactate concentration and lactate increase in competition, thus extending the validity of this scale to sports contests. The Recall of Perceived Exertion scores were not significantly correlated with the duration of effort.

Moderate-intensity muscle pain can be produced and sustained during cycle ergometry

PURPOSE

The aim of this experiment was to determine whether moderate-intensity quadriceps muscle pain could be produced and sustained during cycle ergometry.

METHODS

12 women volunteers completed a peak cycle ergometry test during which quadriceps muscle pain-intensity ratings were obtained using a 0-10 scale. On a subsequent day, participants cycled for 20 min beginning at the power output associated with quadriceps muscle pain threshold during the peak test. Participants manipulated power output during the first 10 s of each minute to produce and sustain moderate-intensity quadriceps muscle pain. During the last 20 s of each minute, VO2, ratings of quadriceps muscle pain intensity, and ratings of perceived exertion (Borg 6-20) were obtained.

RESULTS

Moderate-intensity quadriceps pain ratings were achieved within 4 min, during which time the average power output was increased from 124 to 138 W. Pain-intensity ratings were unchanged from minutes 4 to 20 (F = 0.94; df = 16, 176; P = 0.52; eta2 = 0.079). Quadriceps RPE responses mimicked the pain responses. To sustain a moderate-intensity quadriceps pain participants reduced power output significantly (F = 7.75; df = 16, 176; P < 0.001; eta2 = 0.413) and in a linear fashion by 21.7 W (15.7%). The changes in % VO2peak were similar in pattern to the changes in power output but smaller in magnitude.

CONCLUSIONS

1) College women can produce and sustain a moderate-intensity quadriceps muscle pain during cycle ergometry, 2) moderate-intensity quadriceps muscle pain is sustained by reducing power output, and 3) sustaining moderate-intensity quadriceps muscle pain during short duration cycling is associated with a "hard" perceptual effort and 69-74% VO2peak.

Regulation of exercise intensity using ratings of perceived exertion during passive visual distraction

The purpose of this investigation was to determine if passive visual distraction altered ability to regulate exercise intensity as, assessed by ratings of perceived exertion during a 30-min. treadmill run. 10 trained females (VO2max, 52.7 ml.kg-1.min.-1) performed a graded exercise test on a treadmill to assess maximal aerobic power and rating of perceived exertion, oxygen uptake (VO2), heart rate, and running velocity at the 2.5 mmol.L-1 blood lactate concentration. Subjects then used the target rating of perceived exertion to regulate exercise intensity during a control condition, and two treatment runs with passive visual distractions. During the treatment sessions, the subjects ran on a treadmill while viewing a high-action or a low-action video with no audio. The subjects were allowed to adjust the treadmill speed throughout the run to maintain the target rating of perceived exertion; however, subjects were not allowed to view the speed setting. There were no significant differences in blood lactate concentration among the conditions for the control, low action, high action, or graded exercise test (p < or = .05). No significant differences in VO2 or running velocity were found within or among the 30-min. treatment runs and the graded exercise test. Heart rate at 5 min. of exercise during control (158 +/- 3 b.min.-1), low action (158 +/- 3 b.min.-1), and high action (159 +/- 2 b.min.-1) was significantly lower than the graded exercise test (169 +/- 3 b.min.-1). Based on the data collected, visual passive distraction did not alter regulation of intensity using ratings of perceived exertion during a 30-min. treadmill run.

Repeated bouts of exercise alter the blood lactate-RPE relation

PURPOSE

To examine the effects of repeated bouts of exercise on the blood lactate [HLa]-ratings of perceived exertion (RPE) relation.

METHODS

Six moderately trained males were studied on two occasions: a sequential exercise bouts day (SEB: 1000 h, 1130 h, and 1300 h) and a delayed exercise bouts day (DEB: 1000 h, 1400 h, and 1800 h). Each of the three exercise bouts within a given condition were 30 min in duration at the power output (PO) associated with 70% of VO2peak on a cycle ergometer. A standardized meal was provided at 0600 h. VO2, PO, HR, and RER were recorded every min during exercise and blood [HLa] and RPE were measured every 5 min during exercise.

RESULTS

A 2 x 3 analysis of variance with repeated measures revealed that blood [HLa] decreased significantly with each repeated exercise bout (X +/- SEM: bout 1: SEB = 3.5 (0.3), DEB = 3.8 (0.4); bout 2: SEB = 2.6 (0.3), DEB = 2.8 (0.3); bout 3: SEB = 2.0 (0.2), DEB = 2.1 (0.4); mM). No differences were observed in the blood [HLa] response to repeated bouts of exercise between SEB and DEB. RPE-peripheral (legs, RPE-L) was higher during bout 3 compared with bout 1 (P <0.05) (bout 1: SEB = 11.8 (0.8), DEB = 12.3 (0.2); bout 2: SEB = 12.3 (0.5), DEB = 13.3 (0.4); bout 3: SEB = 13.5 (0.8), DEB = 14.0 (0.7); RPE-central (chest and breathing, RPE-C) was not affected by repeated bouts of exercise, whereas RPE-Overall (RPE-O) was higher during bout 3 compared with bouts 1 and 2 (P < 0.05) (bout 1: SEB = 12.5 (0.2), DEB = 12.3 (0.4); bout 2: SEB = 12.8 (0.4), DEB = 12.7 (0.4); bout 3: SEB = 13.7 (0.7), DEB = 13.2 (0.3)). No interaction for RPE x condition was observed. HR increased with repeated bouts of exercise with HR during exercise bout 3 being higher than HR during exercise bout 1 (164 vs. 156 bpm, P < 0.05). There was also a strong trend for HR during exercise bout 3 to be higher than HR during exercise bout 2 (P < 0.06). A trend for a reduction in VO2 with repeated exercise was observed (P < 0.07), with the reduction apparently related to the SEB condition (P < 0.12 for VO2 x condition). PO and kcal.min-1 were not affected by repeated bouts of exercise. RER decreased significantly with each repeated bout of exercise (from RER = 0.96 to RER = 0.89, P < 0.05) with no difference observed between SEB and DEB.

CONCLUSIONS

We conclude that the blood [HLa]-RPE relation is altered by repeated bouts of exercise and that this alteration does not appear to be affected by recovery time between exercise bouts (up to 3.5 h of recovery). These data suggest that, after the first exercise bout, RPE should not be used to produce a specific blood [HLa] on subsequent exercise bouts.

Validity of rating of perceived exertion during graded exercise testing in apparently healthy adults and cardiac patients

PURPOSE

Recent exercise guidelines recommend a generalized rating of perceived exertion (RPE) range of 12 to 16 (15-point Borg scale) as the perceptual range associated with a physiological training effect. However, whether an individual who selects an RPE within the generalized range during an graded exercise test or exercise training, is actually within the correlated physiological range (50 to 85% maximum oxygen consumption [VO2max]) has not been studied in large samples of apparently healthy individuals or cardiac patients. The purpose of the present study was to assess the validity of the generalized RPE recommendations in a large heterogeneous group of apparently healthy subjects and cardiac patients.

METHODS

Subjects included apparently healthy adults (N = 463) and cardiac patients (N = 217) who presented for a sign-symptom limited maximal graded exercise test (SSLMGXT). Ratings of perceived exertion associated with relative exercise intensities of 60 and 80% of maximal heart rate reserve (MHRR) and peak exercise were selected for analyses.

RESULTS

Significant interindividual variability in RPE was observed at both relative exercise intensities (6 to 20 RPE range at 60% MHRR; 8 to 20 RPE range at 80% MHRR) for both populations. Thirty-nine percent of healthy subjects and 32% of cardiac patients reported an RPE outside an 11 to 14 range at 60% of MHRR, whereas 32% of healthy subjects and 52% of cardiac patients reported an RPE outside of a 14 to 17 range at 80% of MHRR. Peak RPE was higher for the apparently healthy subjects compared with the cardiac patients (18.8 +/- 1.2 versus 16.5 +/- 1.8; P < 0.01).

CONCLUSIONS

These results challenge the applicability of the generalized RPE recommendations described in recent exercise guidelines under typical clinical exercise testing conditions. The basis for the generalized RPE recommendations warrant further investigation. Those who desire to use RPE as a marker of relative exercise intensity during SSLMGXT should take into consideration the large interindividual variability in these measures.