Exercise intensity prescription after myocardial infarction in patients treated with beta-blockers

PURPOSE: The aim of our study was to answer the following questions: (1) Is it possible to estimate the exercise training intensity according to heart rate in patients treated with beta-blockers after myocardial infarction? and (2) Are there any other appropriate alternate possibilities to estimate the training intensity? METHODS: This study involved 112 men (60.2 +/- 8.6 years) with a previous myocardial infarction treated with beta-blockers. Patients underwent exercise echocardiography and also completed a symptom-limited cardiopulmonary ramp test to determine peak exercise capacity, maximal heart rate, heart rate (HR) at the anaerobic threshold (AT), peak oxygen uptake (VO2peak) VO2 consumption at AT, and exercise capacity at AT. RESULTS: The mean value of HR at AT was 104.7 +/- 13.3 bpm, corresponding to 81.0% +/- 8% of VO2peak and 87.9% +/- 5.6% of HRpeak. The mean HR at 80% HRpeak was 96 +/- 13.7 bpm, at 70% heart rate reserve (HRR) 103.3 +/- 13.1 bpm and at 80% HRR 108 +/- 14.4 bpm. A close correlation was observed between HR at AT and values at 80% HRpeak (r = 0.86, P < .01). A similar correlation was found also for 70% and 80% HRR (r = 0.87 and 0.88, respectively, P < .01). Exercise intensity at AT occurred close to the value of 1 W/kg(bodyweight). CONCLUSIONS: As an upper limit in determining training intensities, the assessment of AT is the gold standard. However, findings suggest that %HRpeak, %HRR, and %VO2peak can be used alternatively. The use of workload expressed as in W/kg also appears useful.     

Heart rate recovery--a potential marker of clinical outcomes in heart failure patients receiving beta-blocker therapy

BACKGROUND: Heart rate recovery (HRR) within the first few minutes of graded exercise has been associated with impaired clinical outcomes in patients being evaluated for coronary artery disease. HRR is abnormal in patients with heart failure (HF), but has not been associated with clinical outcomes in these patients. The objective of the present study was to determine whether HRR following cardiopulmonary exercise testing (CPET) correlates with peak oxygen consumption (VO(2)), and whether it impacts clinical outcomes, including HF hospitalizations and total mortality, or the need for cardiac transplantation. METHODS: CPET was performed in 78 patients referred to the Montreal Heart Institute (Montreal, Quebec) with congestive HF between January 2000 and December 2002. All patients had New York Heart Association class II or III HF with a left ventricular ejection fraction of 45% or lower. Mean (+/- SD) age was 53+/-11 years and left ventricular ejection fraction was 27+/-9%. Forty-four per cent had ischemic cardiomyopathy, 88% received beta-blockers and 79% received angiotensin-converting enzyme inhibitors. HRR was defined as the difference from peak exercise HR to HR measured at specific time intervals. HRR was calculated 30 s, 60 s, 90 s and 120 s after exercise. RESULTS: Mean peak VO(2) was 18.0+/-5.3 mL/kg/min, resting HR was 74+/-13 beats/min and peak HR was 119+/-22 beats/min. HRR measured was 10+/-9 beats/min after 30 s, 20+/-12 beats/min after 60 s, 25+/-15 beats/min after 90 s and 30+/-13 beats/min after 120 s. At 90 s, patients with an HRR below 24 beats/min were more likely to have an HF hospitalization at five-year follow-up (eight hospitalizations [22.2%] versus two hospitalizations [2.7%]; P=0.0134). There was a correlation between peak VO(2) and HRR 90 s and 120 s after completion of the exercise test (r=0.40 after 90 s, P=0.001, and r=0.41 after 120 s, P=0.008). CONCLUSIONS: In patients with HF, blunted HRR 90 s and 120 s after CPET correlate with peak VO(2) and are associated with increased risk of worsening HF. HRR is easily measured and a useful marker for morbidity in patients with HF.     

Assessment of exercise intensity formulas by use of ventilatory threshold

Guidelines for training heart rate (HR) during aerobic exercise are often determined by predictive formulas. Measurement of the heart rate at ventilatory threshold (VT) by expired gas analysis provides a direct index of the upper limits of conditioning intensity. We evaluated 115 nonsmoking, healthy adults with measurement of peak oxygen uptake to classify groups as low- (n = 45), average-(n = 45), and high (n = 25) -fitness. Heart rate at VT was compared with the approximate midpoint (77 percent) of recommended training intensity as estimated by the Karvonen equation, predicted maximal (220-age), and measured maximal HR formulas. No significant difference among the various HR formulas at 77 percent and HR at VT were found for high-fitness individuals. Among the low- and average-fitness groups, the Karvonen formula at 77 percent was significantly higher (p less than 0.001) than HR at ventilatory threshold. Predicted and measured maximal HR at 77 percent were not above the VT among the low- and average-fitness individuals and are appropriate for training intensity. However, the Karvonen formula appears to overestimate heart rate intensity among those of low and average fitness and may be excessive for these groups.     

Effects of exercise rehabilitation program on heart rate recovery in patients with chronic heart failure.

BACKGROUND: Heart rate recovery (HRR1) immediately after exercise reflects parasympathetic activity, which is markedly attenuated in chronic heart failure (CHF) patients. The aim of our study was to examine both continuous and interval exercise training effects on HRR1 in these patients. DESIGN: The population study consisted of 29 stable CHF patients that participated at a rehabilitation program of 36 sessions, three times per week. Of the 29 patients, 24 completed the program. Patients were randomly assigned to interval {n=10 [100% peak work rate (WRp) for 30 s, alternating with rest for 30 s]} and to continuous training [n=14 (50%WRp)]. METHODS: All patients performed a symptom-limited cardiopulmonary exercise test on a cycle ergometer before and after the completion of the program. Measurements included peak oxygen uptake (VO2p), anaerobic threshold (AT), WRp, first degree slope of VO2 during the first minute of recovery (VO2/t-slope), chronotropic response [% chronotropic reserve (CR)=(peak HR - resting HR)x100/(220 - age - resting HR)], HRR1 (HR difference from peak exercise to one minute after). RESULTS: After the completion of the rehabilitation program there was a significant increase of WRp, VO2p, AT and VO2/t-slope (by 30%, P=0.01; 6%, P=0.01; 10%, P=0.02; and 27%, P=0.03 respectively for continuous training and by 21%, P<0.05; 8%, P=0.01; 6%, P=NS; and 48%, P=0.02 respectively for interval training). However, only patients exercised under the continuous training regime had a significant increase in HRR1 (15.0+/-9.0 to 24.0+/-12 bpm; P=0.02) and CR (57+/-19 to 72+/-21%, P=0.02), in contrast with those assigned to interval training (HRR1: 21+/-11 to 21+/-8 bpm; P=NS and CR: 57+/-18 to 59+/-21%, P=NS). CONCLUSIONS: Both continuous and interval exercise training program improves exercise capacity in CHF patients. However, continuous rather than interval exercise training improves early HRR1, a marker of parasympathetic activity, suggesting a greater contribution to the autonomic nervous system.     

The importance of heart rate recovery in patients with heart failure or left ventricular systolic dysfunction

BACKGROUND: The ability to better predict outcome with exercise testing in patients with heart failure (HF) and left ventricular systolic dysfunction (LVSD) may prove extremely valuable in determining which patients are at increased risk. This study evaluated the ability of heart rate recovery (HRR) to predict outcome in patients with HF and validate previous findings in LVSD. METHODS AND RESULTS: HRR was measured at 1-, 2-, 3-, and 5-minute time points after treadmill testing in 2,193 males being evaluated for chest pain at the Palo Alto and Long Beach VA Hospitals. Left ventricular ejection fraction (LVEF) was calculated using biplane ventriculography and patients were considered to have LVSD if they had an LVEF <50%. Angiographic and clinical data was available for all patients. Of the 2,193 patients, 314 patients had LVSD and 109 had a history of HF. Both HF patients and patients with LVSD with a normal HRR at 2 minutes had improved survival compared with patients that had an abnormal HRR at 2 minutes when adjusted for age and beta-blocker use (HF adjusted odds ratio 0.25, 95% CI 0.10-0.66, P < .006; LVSD alone adjusted odds ratio 0.25, 95% CI 0.13-0.47, P < .0001). Stepwise proportional hazard regression analysis revealed that only 2-minute HRR, age, LVEF, and chronic obstructive pulmonary disorder were significant predictors of mortality in patients with LVSD and only HRR at 2 minutes and LV hypertrophy were significant predictors of mortality in patients with HF. CONCLUSION: HRR is a significant predictor of mortality in patients with HF and patients with LVSD and may be useful in better determining prognosis.     

Abnormal heart rate recovery immediately after cardiopulmonary exercise testing in heart failure patients

An attenuated heart rate recovery (HRR) immediately after exercise has been shown to be predictive of mortality. It is not known whether HRR predicts mortality when measured in patients with heart failure. The present study was undertaken to evaluate the ability of HRR to predict mortality in patients with heart failure. We studied 84 NYHA class II or III chronic congestive heart failure patients who had a left ventricular ejection fraction < or = 40%. All patients underwent symptom limited cardiopulmonary exercise testing. The value for the HRR was defined as the difference in heart rate between peak exercise and one-minute later; a value < or = 18 beats per minute was considered abnormal. The patients were divided into 2 groups according to the value of HRR. Those with abnormal HRR were assigned to group I and those with normal HRR were assigned to group II. The 2 groups were compared with each other regarding baseline characteristics and exercise capacity assessed by peak VO2. There were 26 patients (31%) in group I and 58 patients (69%) in group II. Group II patients had better performance on treadmill exercise testing than group I patients. They had greater exercise duration (7.5 +/- 3.8 minutes versus 5 +/- 3.5 minutes, P = 0.006), better heart-rate reserve (79 +/- 25% versus 63 +/- 27%, P = 0.01), and higher values of maximal heart-rate (141 +/- 18 beats/min versus 132 +/- 17 beats/min, P = 0.04). Group II patients also had higher peak VO2 values (16.8 +/- 4.4 mL/kg/min versus 14.4 +/- 3.6 mL/kg/min, P = 0.01). When we separated the groups according to beta-blocker usage, beta-blockers had no prominent effect on HRR. In the follow-up period (mean 14.1 +/- 6.1 months), the presence of abnormal HRR and lower peak VO2 (< or = 14 mL/kg/min) were the only significant predictors of mortality in our patient population (adjusted hazard ratio [HR] 5.2, 95% CI, 1.3 to 24, P = 0.03 and adjusted HR 13, 95% CI, 2.1 to 25.6, P = 0.005, respectively). It seems that the attenuated HRR value one minute after peak exercise appears to be a reliable index of the severity of exercise intolerance in heart failure patients and this study supports the value of HRR as a prognostic marker among heart failure patients referred for cardiopulmonary exercise testing for prediction of prognosis.     

Exercise-based cardiac rehabilitation improves heart rate recovery in elderly patients after acute myocardial infarction

BACKGROUND: Heart rate recovery (HRR), defined as the fall in HR during the first minute after exercise, is a marker of vagal tone, which is a powerful predictor of mortality in patients with coronary artery disease and in older patients. Whether exercise training (ET) modifies HRR in elderly patients recovering from acute myocardial infarction (AMI) is still unknown. Therefore, this study aims at evaluating the effect of ET on HRR in elderly AMI patients. METHODS: This was a prospective observational study including 268 older patients after AMI (217 men, 51 women), subdivided in two groups: Group A (n = 104), enrolled in an ET program; Group B (n = 164), discharged with generic instructions to continue physical activity. At baseline and at 3-month follow-up, all Group A and 54/164 Group B patients underwent a cardiopulmonary exercise stress test, whereas 110/164 Group B patients underwent an exercise stress test. RESULTS: After completion of the ET program, in Group A we observed an improvement in oxygen consumption at peak exercise (VO2peak; from 14.7 +/- 1.3 to 17.6 +/- 1.9 mL/kg/min, p < .001), in the rate of increase of ventilation per unit of increase of carbon dioxide production (VE/VCO2slope; from 34.2 +/- 3.8 to 30.4 +/- 3.0, p < .001), and in HRR (from 13.5 +/- 3.7 to 18.7 +/- 3.5 beats/min, p < .001). The changes in VO2peak and in VE/VCO2slope after ET were correlated with the improvement of HRR (r = -0.865, p < .01; r = -0.594, p < .01, respectively). No changes in these parameters were observed in Group B patients. CONCLUSIONS: In older AMI patients, ET results in HRR improvement, which was correlated to the improvement in cardiopulmonary parameters. These findings may shed additional light on the possible mechanisms of the beneficial prognostic effects of ET in this patient population.     

Predicting peak oxygen uptake from 6-min walk test performance in male patients with left ventricular systolic dysfunction

BACKGROUND: In patients with left ventricular systolic dysfunction (LVSD), peak oxygen uptake (pVO2) has strong predictive power for mortality, and can be used to guide management. However, many patients cannot tolerate standard test protocols. The 6-min walk test (6-MWT) is often used to estimate functional capacity due to its simplicity, cost effectiveness and familiarity to patients with LVSD. The relationship between 6-MWT performance and pVO2 is not certain, but if closely related could allow substitution of an expensive and cumbersome test for a cheaper and more familiar one. METHODS AND RESULTS: 120 male patients with LVSD (LVEF <40%; (mean+/-S.D.) age 68+/-13 years; BMI 28+/-5) performed, in random order, a maximal incremental treadmill exercise test with metabolic gas exchange measurements to derive peak oxygen consumption (pVO2 = 19.8+/-5.8 mL.kg(-1).min(-1)), and a standardised 6-MWT (308+/-142 m; r = 0.44; P = 0.00001). In multivariate models including demographic data, resting blood pressure and heart rate, spirometry, routine blood samples, and walk distance, five variables were independently predictive of peak oxygen consumption. pVO2 = 11.92 + (1.48 x FEV1 (L)) + (1.12 x haemoglobin (g dl(-1))) + (0.016 x distance walked (m)) - (0.33 x BMI) - (0.11 x age (years)). This equation accounted for 48% of the variation in pVO2. CONCLUSIONS: Using these five simple variables, peak oxygen consumption can be estimated with moderate accuracy. In clinical practice, however, when an estimate of peak oxygen consumption is required, incremental exercise testing with metabolic gas exchange measurements cannot be avoided in male patients with LVSD. Further work is needed to assess the relation between estimated pVO2 and outcome.     

A comparison of ambulatory oxygen consumption during circuit training and aerobic exercise in patients with chronic heart failure.

PURPOSE: This study compared the exercise intensity of a combined aerobic and resistance exercise circuit training session with the exercise intensity of continuous aerobic exercise in patients with chronic heart failure (CHF). METHODS: Peak oxygen consumption (VO2peak) and muscular strength (1 repetition maximum) were assessed in six CHF patients (age 62 +/- 3 years). Heart rate, rate of perceived exertion (RPE), blood pressures, ambulatory oxygen consumption (VO2), and ventilatory data were measured during two types of exercise: continuous cycling on a bicycle ergometer (aerobic [AER] session) and combined AER and resistance exercise (circuit training [CIR] session). RESULTS: There were no significant differences in VO2, RPE, heart rate, or hemodynamic responses (rate pressure product, diastolic blood pressure, or mean arterial pressure) during exercise, between the two sessions. Systolic blood pressure was significantly lower during CIR (P < 0.05). Minute ventilation and tidal volume were significantly higher (P < 0.0001 and P < 0.01, respectively) and respiratory frequency significantly lower (P < 0.005) during CIR. During CIR, RPE significantly correlated with VO2 (P < 0.01), whereas heart rate did not. Conversely, during the AER session HR correlated with VO2 (P < 0.01), but RPE did not. CONCLUSIONS: Circuit training is a well-tolerated form of exercise training for CHF patients that is associated with similar oxygen and hemodynamic demand to aerobic exercise. Results suggest that RPE may be a better method of prescribing and monitoring exercise intensity during CIR, with heart rate the preferred measure of intensity during aerobic exercise.     

Early heart rate recovery after exercise predicts mortality in patients with chronic heart failure

BACKGROUND: Patients with chronic heart failure (CHF) have multiple abnormalities of autonomic regulation that have been associated to their high mortality rate. Heart rate recovery immediately after exercise is an index of parasympathetic activity, but its prognostic role in CHF patients has not been determined yet. METHODS: Ninety-two stable CHF patients (83M/9F, mean age: 51+/-12 years) performed an incremental symptom-limited cardiopulmonary exercise testing. Measurements included peak O2 uptake (VO2p), ventilatory response to exercise (VE/VCO2 slope), the first-degree slope of VO2 for the 1st minute of recovery (VO2/t-slope), heart rate recovery [(HRR1, bpm): HR difference from peak to 1 min after exercise] and chronotropic response to exercise [%chronotropic reserve (CR, %)=(peak HR-resting HR/220-age-resting HR)x100]. Left ventricular ejection fraction (LVEF, %) was also measured by radionuclide ventriculography. RESULTS: Fatal events occurred in 24 patients (26%) during 21+/-6 months of follow-up. HRR1 was lower in non-survivors (11.4+/-6.4 vs. 20.4+/-8.1; p<0.001). All cause-mortality rate was 65% in patients with HRR112 bpm (log-rank: 32.6; p<0.001). By multivariate survival analysis, HRR1 resulted as an independent predictor of mortality (chi2=19.2; odds ratio: 0.87; p<0.001) after adjustment for LVEF, VO2p, VE/VCO2 slope, CR and VO2/t-slope. In a subgroup of patients with intermediate exercise capacity (VO2p: 10-18, ml/kg/min), HRR1 was a strong predictor of mortality (chi2: 14.3; odds ratio: 0.8; p<0.001). CONCLUSIONS: Early heart rate recovery is an independent prognostic risk indicator in CHF patients and could be used in CHF risk stratification.     

Initial and final exercise heart rate transients: influence of gender, aerobic fitness, and clinical status

STUDY OBJECTIVES: To compare the independent and additive data provided by initial and final heart rate (HR) exercise transients, and to analyze both according to gender, aerobic fitness, clinical status, and medication usage. DESIGN: Retrospective study. SETTING: Exercise medicine clinic. PATIENTS: A total of 544 subjects (363 men) with a mean (+/- SD) age of 50 +/- 14 years (age range, 10 to 91 years), including asymptomatic and coronary artery disease patients. MEASUREMENTS AND RESULTS: HR transients were obtained from the following two exercise protocols: 4-s exercise test (4sET) followed by a maximal cardiopulmonary cycling exercise test (CPET). The initial HR transient was represented by the cardiac vagal index (CVI), which was obtained by the 4sET, and the final transient (ie, HR recovery [HRR]) was determined by the following equation: CPET maximal HR - the 1-min postexercise HR. Transients were modestly related (r = 0.22; p < 0.001) when adjusted for age, aerobic fitness, clinical status, and negative chronotropic action drug usage. The transients were unrelated to gender (vs CVI, p = 0.10; vs HRR, p = 0.15). Subjects with a measured maximum oxygen uptake (VO2max) exceeding 100% of the predicted maximal aerobic power showed higher CVIs than those in less aerobically fit subjects (VO2max < 50% subgroup, p = 0.009; VO2max < 75% subgroup, p = 0.034). Both transient results differed for asymptomatic and cardiac subjects (CVI, 1.32 +/- 0.02 vs 1.42 +/- 0.02, respectively [p = 0.001]; HRR, 33 +/- 1 beats/min (bpm) vs 37 +/- 1 bpm, respectively [p = 0.009]). CONCLUSIONS: The initial and final HR transients were modestly related, suggesting a potentially complementary clinical role for both measurements in the assessment of autonomic function in patients with coronary artery disease. Although both HR transients tended to behave similarly under the influence of several variables, the initial HR transient, measured during 4sET, was more likely to discriminate distinct subgroups compared with the final HR transient.     

Re-evaluation of exercise intensity for overweight Japanese men by ventilatory threshold

AIM: To re-evaluate exercise intensity for overweight Japanese men by ventilatory threshold (VT). METHODS: Cross sectional clinical intervention study. Subjects and materials: One hundred and ten overweight Japanese men aged 32-59 years were recruited. The average body mass index was 28.5+/-2.5 kg/m(2). Aerobic exercise level was evaluated by measuring VT. Fifty per cent heart rate (HR) reserve by Karvonen's formula was calculated and compared with HR at VT. Fat distribution was evaluated by visceral fat and subcutaneous fat areas measured with computed tomography scanning at umbilical levels. Anthropometric parameters such as height, body weight and body fat percentage were also measured. RESULTS: There was significant correlation between HR at VT and 50% HR reserve by Karvonen's formula (r=0.642, p<0.01). However, HR at VT was significantly lower than 50% HR reserve by Karvonen's formula (HR at VT 103.6+/-10.6 beat/min vs. 50% HR reserve 125.0+/-7.1 beat/min, p<0.01) and HR at VT was corresponded to 28.5+/-8.3% HR reserve by Karovonen's formula. CONCLUSION: The present study indicated that exercise intensity of 30% HR reserve should be recommended for overweight Japanese men.     

Long-term effects of cardiac rehabilitation on end-exercise heart rate recovery after myocardial infarction.

BACKGROUND: Heart rate recovery (HRR) is a marker of vagal tone that is a powerful predictor of mortality in patients with coronary artery disease. DESIGN: This study aims at evaluating the effects of long-term exercise training on HRR after acute myocardial infarction (AMI), in order to clarify whether prolonged exercise training could maintain a long-term improvement of HRR. METHODS: Forty-four patients after AMI were enrolled in a 3-month hospital-based exercise training programme. At the end, patients were subdivided into two groups: group A (n=22), patients discharged with a specific home-based exercise training programme and instructions for improving leisure-time physical activity; group B (n=22), patients discharged with generic instructions to maintain physical activity. All patients underwent a cardiopulmonary exercise test before, at the end of 3 months exercise training and at 6 months follow-up. RESULTS: At the end of the hospital-based exercise training programme we observed an increase in peak oxygen consumption [VO2peak; from 13.9+/-3.6 to 18+/-2.7 ml/kg per min (A) and from 14.1+/-3.9 to 17.9+/-2.1 ml/kg per min (B), P<0.001] and in HRR [from 17.1+/-1.8 to 23.4+/-1.4 beats/min (A), and from 18.8+/-2.1 to 24.3+/-1.9 beats/min (B), P<0.001]. At 6 months' follow-up we observed a further improvement in VO2peak (from 18.0+/-2.7 to 20.3+/-2.7 ml/kg per min, P<0.001) and in HRR (from 23.4+/-1.4 to 27.8+/-2.1 beats/min, P<0.001) in group A, but a significant decrease in VO2peak and in HRR in group B (P<0.001). CONCLUSION: Long-term exercise training is useful for maintaining or improving the beneficial results of the standard 3-month exercise training programme on cardiovascular capacity and HRR. This observation may bear beneficial prognostic effects on patients after AMI.     

Determination of exercise training heart rate in patients on beta-blockers after myocardial infarction.

BACKGROUND: In patients with coronary artery disease, the target intensity-level of exercise training is usually based on a training heart rate that aims to be close to the upper level of metabolic aerobic exercise. AIM: We intended to evaluate whether a training heart rate calculated with the Karvonen formula after a conventional exercise test is comparable with the heart rate at the anaerobic threshold in patients after myocardial infarction treated with beta-blockers and if not to propose a new formula. METHODS AND RESULTS: In this multicenter prospective study, 115 consecutive beta-blocked patients recovering from myocardial infarction performed a cardiopulmonary exercise test to determine the anaerobic threshold. The training heart rate determined by the Karvonen formula was compared with the heart rate at the anaerobic threshold in a derivation sample (n=58) and a validation sample (n=57) of patients. The Karvonen training heart rate was significantly lower than the heart rate at the anaerobic threshold (91+/-5 versus 102+/-17 bpm, P<0.0001) in the first sample of patients and this difference was clinically relevant in 40% of patients. Thus, a 'modified Karvonen training heart rate', equal to 0.8xx(maximum heart rate-resting heart rate)+resting heart rate, was calculated by linear regression in the derivation sample and prospectively assessed in the validation sample. The modified Karvonen training heart rate was closer to the heart rate at the anaerobic threshold than the Karvonen training heart rate, and the difference between the modified Karvonen training heart rate and the heart rate at the anaerobic threshold was clinically relevant in only 5% of patients. CONCLUSION: The Karvonen formula underestimates the heart rate at the anaerobic threshold in beta-blocked patients, which may lead to undertraining of patients with coronary artery disease; we propose another formula more adapted to these patients.     

Physiological responses to high intensity, constant-load arm exercise in COPD

The aim of the study was to compare the metabolic, ventilatory and dyspnoea responses of a single bout of high intensity, constant-load arm exercise to peak arm exercise in people with chronic obstructive pulmonary disease (COPD). Thirty people with COPD (mean age+/-SD=65+/-8 years; FEV1% predicted=56+/-12%) were included. All subjects performed an incremental arm exercise test to peak work capacity on an arm ergometer and, on a separate day, a constant-load arm exercise test at 80% of the peak work rate achieved on the incremental test. Throughout both exercise tests, oxygen consumption (VO2), minute ventilation (VE), dyspnoea and rate of perceived exertion (RPE) were measured each minute. Peak work rate on the incremental test was 33.0+/-10.1 W with a mean duration of 6.6+/-2.0 min. The mean duration of the constant-load test of 7.1+/-2.9 min was not significantly different to the incremental test (p=0.3). At end exercise, VE, dyspnoea and RPE for the constant-load test was significantly higher compared to the incremental test (VE: 41.3+/-14.4 L/min and 38.3+/-11.8 L/min; dyspnoea: 5.6+/-2.7 and 4.6+/-2.1; RPE: 7.1+/-2.3 and 6.0+/-2.0; all p<0.05). Constant-load arm exercise at 80% peak work rate elicits higher ventilatory, dyspnoea and RPE responses at end exercise compared to incremental arm exercise in people with COPD. This finding suggests that an intensity of 80% peak work rate may be too high as an initial training intensity for supported arm exercise in people with COPD.     

Decreased heart rate recovery after exercise in patients with congestive heart failure: effect of beta-blocker therapy

BACKGROUND: Decreased heart rate recovery (HRR) is a predictor of mortality in patients with coronary artery disease and preserved left ventricular function. We investigated the changes in HRR and assessed the impact of beta-blockade therapy on these parameters in patients with symptomatic congestive heart failure (CHF). METHODS AND RESULTS: HRR, defined as the difference from peak exercise heart rate (HR) to HR measured at 1, 2, and 3 minutes after maximal exercise test, was studied in 23 stable CHF patients and 12 healthy subjects. Patients with CHF performed a maximal exercise test using a Ramp protocol before and after 6 months of therapy with either metoprolol or carvedilol. Patients with CHF exhibited a significantly attenuated HRR compared with healthy subjects at 1 minute (17.8 +/- 5.8 versus 26.8 +/- 16.2 beats), 2 minutes (34.0 +/- 10.6 versus 48.0 +/- 11.2 bpm) and 3 minutes (41.0 +/- 12.4 versus 60.0 +/-12.4 bpm) after exercise (P<.05 for all parameters). Beta-blocker therapy for 6 months did not significantly improve HRR. CONCLUSION: HRR is markedly attenuated in stable CHF patients compared with healthy subjects. Long-term beta-blocker therapy appears to cause no significant improvement in HRR up to 3 minutes after maximal exercise.