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.     

Different methods for monitoring intensity during water-based aerobic exercises

The aim of this study was to compare different measurement techniques (indirect calorimetry, IC; heart rate monitoring, HR; an activity monitoring system, AH; rates of perceived exertion, RPE) to estimate physical activity intensity (light, moderate, vigorous) during water-based aerobic exercises (WE). Twelve healthy young women performed five common WE of 10-min duration at three frequencies in an indoor swimming pool. Data recorded from the 5th to 9th minute of exercise were averaged to obtain mean [(V)\dot]\text O₂ {\dot V}\text O_2 (IC), HR and AH values; RPE was recorded at the end of each WE. Oxygen uptake was also estimated from HR data using three different [(V)\dot]\text O₂ {\dot V}\text O_2 versus HR regression equation models. Significant correlations (p < 0.001) were found for the indirect methods that used HR, RPE and AH data regressed as a function of [(V)\dot]\text O₂ {\dot V}\text O_2 (IC); the highest correlations were found between the measured values of [(V)\dot]\text O₂ {\dot V}\text O_2 (IC) and those estimated from the three [(V)\dot]\text O₂ {\dot V}\text O_2 versus HR equations (R > 0.7 in all cases). An ANOVA test showed no significant differences between all predicted and measured [(V)\dot]\text O₂ {\dot V}\text O_2 values; however, when the Bland & Altman analysis was considered, AH data showed the larger explained variances (95% CI) and the larger standard errors. These data indicate that the most accurate way to estimate physical activity intensity during WE is based on HR measurements.     

Regulating intensity using perceived exertion during extended exercise periods

The present study was undertaken to examine the validity of using the OMNI scale of perceived exertion to regulate intensity during extended exercise periods. Forty-eight subjects (24 male, 24 female) were recruited and each subject completed a maximal graded exercise test (GXT) and two 20-min submaximal exercises. During the GXT, ratings of perceived exertion (RPE) as well as oxygen uptake (V˙O₂) and heart rate (HR) equivalent to 50 and 70% of maximum V˙O₂ (V˙O_2max) were estimated. During each submaximal exercise, subjects were instructed to produce and maintain a workload equivalent to the RPE estimated at 50 or 70% V˙O_2max, and V˙O₂ and HR were measured every 5 min throughout the exercise. Of the 48 subjects, 12 (6 male and 6 female) performed both the estimation and production trials on a treadmill (TM/TM), 12 (6 male and 6 female) performed both the estimation and production trials on a cycle ergometer (C/C), 12 (6 male and 6 female) performed the estimation trial on a treadmill and the production trial on a cycle ergometer (TM/C), and 12 (6 male and 6 female) performed the estimation trial on a cycle ergometer and the production trial on a treadmill (C/TM). No differences in V˙O₂ between the estimation and any 5 min of the production trial were observed at either intensity in TM/TM and C/C. No differences in HR between the estimation and any 5 min of the production trial were also observed at 50% V˙O_2max in TM/TM and at both 50 and 70% V˙O_2max in C/C. However, HR was higher at 20th min of the production trial at 70% V˙O_2max in TM/TM. Both the V˙O₂ and HR were generally lower in TM/C and higher in C/TM. However, these differences diminished when values were normalized using V˙O_2max of the same mode that other groups had attained. These data suggest that under both intra- and intermodal conditions, using the OMNI perceived exertion scale is effective not only in establishing the target intensity at the onset of exercise, but also in maintaining the intensity throughout a 20-min exercise session. Electronic Publication     

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.     

Effect of exercise duration on session RPE at an individualized constant workload

Session RPE (SRPE) permits subjective ratings of global effort following exercise. SRPE is useful for evaluating training load; however, mediating factors are not well understood. This study compared SRPE among treadmill trials at a clamped workload with a varied duration. Ten subjects (VO₂max: 48.9 ± 10.5 ml kg⁻¹ min⁻¹) completed a maximal-exertion treadmill trial followed by treadmill trials of 20 (TM20), 30-(TM30), and 40-(TM40) min (counterbalanced) duration at approximately 70% individualized VO₂max. Heart rate (HR) and acute RPE (during exercise) were recorded every 5 min with blood lactate concentration [La] recorded before initiating exercise and every 10 min throughout exercise to completion. Analyses showed no significant differences among TM20, TM30, and TM40 for mean HR, [La] or acute RPE which isolated effects of duration on SRPE. Session RPE (recorded 20 min post exercise) relative to overall (SRPEO), legs (SRPEL) and breathing (SRPEB) was analyzed using a 3 (trial) × 3 (SRPE: O, L, B) repeated measures ANOVA (alpha 0.05). There was no main effect for duration, but there was a significant main effect for SRPE type with SRPEO (4.40 ± 2.18) greater than SRPEB (3.56 ± 1.98) but no difference for SRPEL (4.43 ± 2.16). Follow-up tests for within-trial differences showed no significant differences for SRPEL versus SRPEO, but blunted SRPEB estimations (vs. SRPEO and SRPEL). Primary results indicate affects of duration on SRPE are minimal. Further, within the limits of the current study, differentiating SRPE estimations do not appear advantageous; however, further work is warranted.     

Influence of intensity fluctuation on exercise metabolism

This investigation was undertaken to examine the influence of intensity fluctuation on metabolic responses during and after exercise. Twenty-four males and 24 females were randomly assigned into one of the four groups consisting of 12 subjects of equal gender. Each group performed one of four 30-min exercise protocols: (1) cycling at a constant power output of 75 W (P1), (2) cycling with power output alternating between 50 and 100 W every 5 min (P2), (3) same as P2 except power output was alternated in a reverse order (P3), and (4) same as P2 except power output was alternated between 25 and 125 W (P4). Each exercise session was followed by a 25-min recovery and all protocols yielded the same mechanical work. Oxygen uptake (VO₂), heart rate (HR), respiratory exchange ratio (RER), and plasma lactate concentrations ([La]) were measured at rest and during exercise and recovery. Ratings of perceived exertion (RPE) were recorded during exercise only. During exercise, VO₂, HR and RPE did not differ across the four protocols. RER was higher (P < 0.05) in P4 than P1 and P2. [La] was higher (P < 0.05) in P4 than P1 and P3. During recovery, VO₂ were lower (P < 0.05) in P1 than P2, P3, and P4, while [La] was higher in P4 than P3. When the total workload was equated, intensity fluctuation exerted no added effect upon metabolic responses during exercise, but provoked greater energy expenditure following exercise. Reversing the order or increasing the magnitude of intensity fluctuation would not further alter metabolic consequences.     

Estimation of %V˙O2 reserve from heart rate during arm exercise and running

The purpose of the present investigation was to examine the relationship between the percent heart rate reserve (%HRR) in arm exercise and the corresponding percent oxygen uptake (V˙O₂) reserve, and to compare this relationship to that occurring in running. Fourteen male physical education students took part in the study. Each subject performed a maximal running exercise test and a maximal arm cycling test. The subjects also performed three submaximal exercise bouts (in both exercise modes) at 30%, 60% and 80% of their HRR. The subjects were monitored for their heart rate (HR) at rest, maximal HR (HR_max), HR at submaximal work loads, maximal V˙O₂ (V˙O_2max), V˙O₂ at rest and V˙O₂ at submaximal loads. For each subject, load and exercise mode, %HRR and %V˙O₂ reserve were calculated (from HR_max and V˙O_2max as measured during running and arm cycling) and the relationship between the two was evaluated. The main finding of the present investigation is that the prediction of %V˙O₂ reserve in arm cycling from %HRR is grossly overestimated when calculated from HR_max and V˙O_2max measured during running. The prediction is better but still overestimated when calculated from HR_max and V˙O_2max measured during arm cycling. The findings indicate a better prediction of %V˙O₂ reserve from %HRR for running than for arm exercise. These findings should be taken into consideration when prescribing the target HR for arm training. Accepted: 24 July 2000     

Non-invasive evaluation of gas exchange during a shuttle walking test vs. a 6-min walking test to assess exercise tolerance in COPD patients

Walking tests, such as the "shuttle" incremental walking test (SWT) and the 6-min walking test (6'WT), are commonly utilized in evaluating exercise intolerance in patients with chronic obstructive pulmonary disease (COPD) and the distance covered is the variable usually considered. Because lung gas exchange indexes are not measured, little is known about the physiological response elicited by different walking protocols. We compared exercise adaptation during the 6'WT and SWT in 13 male stable COPD patients [mean (SE) age: 70 (1) years; forced expiratory volume in 1 s (FEV₁): 1.2 (0.1) l; arterial O₂ tension (PaO₂): 72 (2) mmHg; arterial CO₂ tension (PaCO₂): 41 (1) mmHg]. Oxygen uptake (V˙O₂), CO₂ output (V˙CO₂), minute ventilation (V˙ _E), and heart rate (HR) were monitored by a portable telemetric system. During the SWT a linear response in lung gas exchange indexes was observed while, during the 6'WT, the response was exponential. During the 6'WT, V˙O₂, V˙CO₂, V˙ _E, and HR values at steady-state (SS) were significantly lower compared to SWT peak values. For SWT, distance covered correlated with V˙O_2PEAK (R=0.86, p<0.001), V˙CO_2PEAK (R=0.87, p<0.001) and V˙ _EPEAK (R=0.74, p<0.01); moreover, distance and V˙O_2PEAK were significantly correlated with peak V˙O₂ values obtained during cycle ergometer incremental exercise (R=0.72, p<0.01 and R=0.92, p<0.0001, respectively). For 6'WT, the distance covered did not correlate with any pertinent physiological index. The two walking protocols reveal substantial differences in pathophysiologic adaptations and provide evidence that SWT is more accurate than the 6'WT in the evaluation of maximal exercise tolerance in COPD patients. Electronic Publication     

Cerebral oxygenation is reduced during hyperthermic exercise in humans

Aim: Cerebral mitochondrial oxygen tension (P_mitoO₂) is elevated during moderate exercise, while it is reduced when exercise becomes strenuous, reflecting an elevated cerebral metabolic rate for oxygen (CMRO₂) combined with hyperventilation-induced attenuation of cerebral blood flow (CBF). Heat stress challenges exercise capacity as expressed by increased rating of perceived exertion (RPE). Methods: This study evaluated the effect of heat stress during exercise on P_mitoO₂ calculated based on a Kety-Schmidt-determined CBF and the arterial-to-jugular venous oxygen differences in eight males [27 ± 6 years (mean ± SD) and maximal oxygen uptake (VO_2max) 63 ± 6 mL kg⁻¹ min⁻¹]. Results: The CBF, CMRO₂ and P_mitoO₂ remained stable during 1 h of moderate cycling (170 ± 11 W, ∼50% of VO_2max, RPE 9–12) in normothermia (core temperature of 37.8 ± 0.4 °C). In contrast, when hyperthermia was provoked by dressing the subjects in watertight clothing during exercise (core temperature 39.5 ± 0.2 °C), P_mitoO₂ declined by 4.8 ± 3.8 mmHg (P < 0.05 compared to normothermia) because CMRO₂ increased by 8 ± 7% at the same time as CBF was reduced by 15 ± 13% (P < 0.05). During exercise with heat stress, RPE increased to 19 (19–20; P < 0.05); the RPE correlated inversely with P_mitoO₂ (r² = 0.42, P < 0.05). Conclusion: These data indicate that strenuous exercise in the heat lowers cerebral P_mitoO₂, and that exercise capacity in this condition may be dependent on maintained cerebral oxygenation.     

Effect of push frequency and strategy variations on economy and perceived exertion during wheelchair propulsion

Wheelchair locomotion is a cyclical activity and participants are free to select any push frequency–propulsion strategy combination that suits their needs at a given power output. The aim of the study was to examine the physiological effects of varying push frequency and strategy on pushing economy. Twelve male, able-bodied participants completed four, randomly assigned, 5-min bouts of submaximal exercise at 32 W on a wheelchair ergometer. Each bout of exercise combined two different push frequencies (40 and 70 push min^–1), with one of two different push strategies [synchronous (SYN): both arms pushing together, and asynchronous: one arm applying force to the wheel at a time). Physiological measures included oxygen uptake (O₂), heart rate (HR) and blood lactate [La]_b concentration. Differentiated ratings of perceived exertion (RPE) were also recorded (overall, local and central). Separate ANOVA were used for O₂, HR, [La]_b and RPE as the dependent variables. Where significant differences were identified, a Bonferroni post hoc test was used. The main effect for push frequency by strategy was significant for O₂ (P<0.01). Scrutiny of the HR values showed that the SYN 40 condition was significantly less stressful than all other frequency–strategy combinations (P<0.01). RPE data supported these findings although they were found to be non-significant. When looking at [La]_b, both of the main effects were also significant showing the concentration was lower on average when the push rate was 40 as opposed to 70 (1.65 vs 2.14 mmol l^–1; P<0.01). This study provides further evidence that a low push frequency provides the most economical form of wheelchair propulsion especially when combined with a SYN strategy.     

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.     

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.     

Exercise during hyperoxia and hyperbaric oxygenation

Physiological reactions during exercise were tested under hyperoxic and hyperbaric conditions. In 6 subjects walking and running at increasing speeds on a treadmill, maximum performance showed little change when the respired air was enriched with O₂. Maximum metabolism, measured by CO₂ production, increased by 3.2%. During exercise on a bicycle ergometer, maximum O₂ uptake increased by 3% in 5 subjects breathing pure O₂ at 1 ATA. During hyperoxia the maximum O₂ consumption measured at 2 and 3 ATA did not differ significantly from that measured at 1 ATA. Heart rate showed highly comparable maximum values under the various experimental conditions. During submaximal exercise, heart rate was consistently lower when the subjects breathed O₂. The O₂-linked difference became slighter with every increase in work load. Under hyperbaric and hyperoxic conditions, ventilation was invariably reduced during exercise.     

Downhill walking induces rapid shallow breathing

To examine the effect of downhill walking a form of negative work on ventilation, we studied the exercise responses of 13 healthy subjects during uphill and downhill walking on a treadmill. Each test lasted 16 min and the peak work rate was 5.6 kph with either a positive or negative 14% grade. Throughout each test we recorded V _O2, V _E, f, V _T, HR, systolic BP and Borg's rating of perceived exertion. At the target work rates of 5.6 kph ± 14% grade, V _O2 and V _E were three times greater in uphill compared with downhill walking. However, in downhill walking, f was greater compared with uphill walking wherein V _T approximated baseline values, reflecting rapid shallow breathing, and V _T appeared to increase after reaching some critically-low level. These trends persisted when V _O2 was held constant (p<0.01). HR and systolic BP increased and decreased with the positive and negative grade respectively. At a constant V _O2 however, HR was significantly higher during downhill compared with horizontal walking (p<0.01) whereas systolic BP was not significantly different (p>0.05). We conclude that there is a significant difference in the ventilatory responses between the two types of work performed on a treadmill. Specifically, downhill walking is associated with rapid shallow breathing which may be countered by a protective feedback mechanism at critically-low levels of V _T.     

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.     

Dependence of lactate removal on muscle metabolism in man

Summary If lactate is primarily oxidized in skeletal muscle in man, it is expected that lactate uptake would increase linearly with increasing muscle metabolism (VO₂). Therefore, lactate removal was investigated (N=9) after 6 min exercise bouts (90% VO₂ max), at rest, and during 30 min of recovery exercise, when the relative intensities were constant to equate lactate production while permitting exercise metabolism (VO₂) to vary. Recovery exercises were therefore conducted at 26.8% VO₂ max for arm exercise, 26.8% VO₂ max for leg exercise, and 29% VO₂ max for combined arm and leg exercise. These exercise intensities were calculated from VO₂ max values established separately for each of the three modes of exercise. Lactate removal was slowest at rest (p<0.05). Removal during leg recovery was faster than during the arm condition (p<0.05), but the leg removal was not different from the combined arm and leg condition (p>0.05). The VO₂ cost of the arm (0.73±0.04 l/min), leg (1.04±0.05 l/min) and combined arm and leg exercise (1.23±0.10 l/min) were distinctly different from each other (p<0.05). There was a high correlation (r=0.92) between VO₂ cost, and the lactate removal rates of the corresponding recovery conditions. These findings indicate that lactate increases proportionately with the metabolically active muscle mass, providing exercise remains aerobic. Thus in man, it appears that lactate removal from the blood during recovery exercise occurs primarily in skeletal muscle.     

Reproducibility of the blood lactate threshold, 4 mmol·l<Superscript>–1</Superscript> marker,heart rate and ratings of perceived exertion during incremental treadmill exercise in humans

The aim of this study was to investigate the reproducibility of blood lactate measurements, heart rate (HR) and ratings of perceived exertion (RPE) during treadmill exercise at speeds corresponding to the lactate threshold (v _Th,la-) and a fixed blood lactate concentration of 4 mmol·l^–1(v _la-_,4). Possible differences in reproducibility related to fitness levels were also investigated. A group of 20 men [mean (SD)] [age 20.5 (1.4) years] and 16 women [age 21.2 (0.9) years] took part in the study. The subjects performed two identical incremental exercise tests consisting of at least six 4 min stages. Blood lactate concentrations, HR and RPE were recorded at the end of each stage. Limits of agreement (LoA), correlation coefficients and 95% confidence intervals for the mean difference between tests were employed to investigate the level of agreement and reproducibility of blood lactate concentration, HR and RPE. For the group as a whole, the sample correlation coefficient for speed at v _Th,la- was r=0.88, and was r=0.92 for the speed at v _la-_,4. At v _Th,la -, the correlation coefficients for the moderately fit and unfit were r=0.94 and r=0.36, respectively, and at v _la-_,4 r=0.93 and r=0.68, respectively. The LoA for the moderately fit group indicated that a change of 1.62 km·h^–1 in v _Th,la- would be necessary to be considered a change in training status. For HR and RPE, relationships between the tests were generally poor. The LoA suggested that changes in scores must be unacceptably large. These findings cast doubt on the sensitivity of testing for change of blood lactate concentration, HR and RPE in this population. Electronic Publication     

Bronchodilator effect on ventilatory,pulmonary gas exchange,and heart rate kinetics during high-intensity exercise in COPD

Respiratory mechanical abnormalities in patients with chronic obstructive pulmonary disease (COPD) may impair cardiodynamic responses and convective oxygen delivery during exercise, resulting in slower ventilatory, pulmonary gas exchange (PGE), and heart rate (HR) kinetics compared with normal. We reasoned that bronchodilators and the attendant reduction of operating lung volumes should accelerate ventilatory, PGE, and HR kinetics in the transition from rest to high-intensity exercise. Twelve clinically stable COPD patients undertook constant-work rate cycle testing at 75% of each individual’s maximum work capacity after receiving either combined nebulized bronchodilators (BD) or placebo (PL), randomly. Mean response time (MRT) and amplitude of slow component for oxygen uptake (V′O₂), carbon dioxide production (V′CO₂), ventilation (V′_E), and HR together with operating dynamic end-expiratory lung volume (EELV) were measured. Resting and exercise EELV decreased significantly by 0.38 L after BD compared with PL. After BD, V′O₂, V′CO₂, V′_E, and HR MRT accelerated (p < 0.05) by an average of 12, 22, 27, and 22 s, respectively (i.e., 15, 18, 22 and 27%, respectively). The slow component for V′O₂ declined by an average of 55 ml/min compared with PL. Speeded MRT for V′O₂ correlated with indices of reduced lung hyperinflation, such as resting EELV (r = −0.64, p = 0.025) and EELV at isotime (r = −0.77, p = 0.0032). The results confirm an important interaction between abnormal dynamic respiratory mechanics and indices of cardio-circulatory function in the rest-to-exercise transition in COPD patients.     

Accuracy of pulse oximetry during intense exercise under severe hypoxic conditions

There is a growing need to measure arterial oxygen saturation with a non-invasive method during heavy exercise under severe hypoxic conditions. Although the accuracy of pulse oximetry has been challenged by several authors, it has not been done under extreme conditions. The purpose of this study was to evaluate the accuracy of a pulse oximeter (Satlite, Datex, Finland) during exercise under hypoxic conditions where arterial oxygen saturation was below 75%, simulating exercise at extreme altitude. Ten healthy non-smoking men performed two exercise studies of 30?min under normoxia and under hypoxia on two consecutive days. The exercise intensity was 80% of maximal O₂ consumption of O_2max. Arterial oxygen saturation measured by pulse oximetry was corrected (S _pO_2[corr]) according to previously published equations and was compared to arterial oxygen saturation (S _aO₂) in blood samples taken simultaneously from the radial artery. Reference arterial saturation values ranged from 57.2 to 97.6% for the whole data set. This data set was split according to low (S _aO₂?≤?75%) and high (S _aO₂?>?75%) S _aO₂ values. The error of pulse oximetry (S _pO_2[corr]? S _aO₂) was 2.05 (0.87)% [mean (SD)] and 1.80 (1.81)% for high and low S _aO₂ values, respectively. S _pO_2[corr] and S _aO₂ were highly correlated (r?=?0.93, SEE?=?1.8) for low values. During high-intensity constant workload under severe hypoxic conditions, once corrected, pulse oximetry provides an estimate of S _aO₂ with a mean error of 2%. Thus, the correction previously described for S _pO₂ values above 75% saturation applies also to S _pO₂ values in the range of 57–75% during exercise under hypoxic conditions.