Test-retest reproducibility of heart rate recovery after treadmill exercise

Long-term intra-individual reproducibility of heart rate dynamics during exercise and recovery in the UK Biobank cohort

Background

The heart rate (HR) response to exercise provides useful information about the autonomic function and has prognostic value, but its reproducibility over a long period of time, a critical requirement for using it as a clinical biomarker, is undetermined.

Aim

To determine the intra-individual reproducibility of HR dynamics during sub-maximum exercise and one minute recovery.

Methods

1187 individuals from the Cardio physical fitness assessment test of the UK Biobank repeated a standard exercise stress test twice (recall time 34.2 ± 2.8 months) and were prospectively studied.

Results

821 individuals complied with inclusion criteria for reproducibility analysis, including peak workload differences between assessments ≤10 W. Intra-individual correlation between HR profile during the first and the second assessment was very high and higher than inter-individual correlation (0.92±0.08 vs 0.87±0.11, p<0.01). Intra-individual correlation of indices describing HR dynamics was: ρ = 0.81 for maximum HR during exercise; ρ = 0.71 for minimum HR during recovery; ρ = 0.70 for HR changes during both exercise and recovery; Intra-individual correlation was higher for these indices of HR dynamics than for resting HR (ρ = 0.64). Bland-Altman plots demonstrated good agreement between HR indices estimated during the first and second assessment. A small but consistent bias was registered for all repeated measurements. The intra-individual consistency of abnormal values was about 60–70%.

Conclusions

The HR dynamics during exercise and recovery are reproducible over a period of 3 years, with moderate to strong intra-individual reproducibility of abnormal values.

Comparison between treadmill and bicycle ergometer exercise tests in mild-to-moderate hypertensive Nigerians

BACKGROUND

Comparative cardiovascular responses to treadmill and bicycle ergometer (bike) exercise tests in hypertensive Nigerians are not known. This study compared cardiovascular responses to the two modes of exercise testing in hypertensives using maximal exercise protocols.

METHODS

One hundred and ten male subjects with mild-to-moderate hypertension underwent maximal treadmill and bike test one after the other at a single visit in a simple random manner. Paired-sampled t-test was used to compare responses to both exercise tests while chi-squared test was used to compare categorical variables.

RESULTS

The maximal heart rate (P<0.001), peak systolic blood pressure (P=0.02), rate pressure product (P<0.001), peak oxygen uptake (P<0.001), and exercise capacity (P<0.001) in metabolic equivalents were signifcantly higher on the treadmill than on the bike.

CONCLUSION

Higher cardiovascular responses on treadmill in Nigerian male hypertensives in this study, similar to findings in non-hypertensives and non-Nigerians in earlier studies, suggest that treadmill may be of better diagnostic utility in our population.

Heart rate recovery: a practical clinical indicator of abnormal cardiac autonomic function

The autonomic nervous system (ANS) and cardiovascular function are intricately and closely related. One of the most frequently used diagnostic and prognostic tools for evaluating cardiovascular function is the exercise stress test. Exercise is associated with increased sympathetic and decreased parasympathetic activity and the period of recovery after maximum exercise is characterized by a combination of sympathetic withdrawal and parasympathetic reactivation, which are the two main arms of the ANS. Heart rate recovery after graded exercise is one of the commonly used techniques that reflects autonomic activity and predicts cardiovascular events and mortality, not only in cardiovascular system disorders, but also in various systemic disorders. In this article, the definition, applications and protocols of heart rate recovery and its value in various diseases, in addition to exercise physiology, the ANS and their relationship, will be discussed.

The reproducibility of heart rate recovery after treadmill exercise test

BACKGROUND

Although predictive value of heart rate recovery (HRR) has been tested in large populations, the reproducibility of HRR in treadmill exercise test has not been assessed prospectively. This prospective study examined whether HRR index has test-retest stability in the short term.

METHODS

A total of 52 healthy volunteers without cardiovascular risk factors (mean age, 30 ± 10 years, 30 females) underwent standardized graded treadmill exercise test, and the test was repeated on the 7th and the 30th days. The subjects' maximal heart rates and the decrease of heart rate from the peak exercise level to the level of 1, 2, 3, 4, and 5 minutes after the termination of the exercise were examined on each test, and heart rates for each minute from the first, second, and third tests were compared for each individual.

RESULTS

The maximal heart rates on the 1st, 7th, and the 30th days were 179 ± 11, 177 ± 10, 178 ± 10 beats/min, respectively [P = 0.07, intraclass correlation coefficient (ICC) = 0.92], and the 1st minute HRR indices after peak exercise were 33 ± 10, 33 ± 10, 33 ± 11, respectively (P = 0.66, ICC = 0.88). There was no statistical difference in the 2nd, 3rd, 4th, and 5th minute heart rates of the recovery phase among the 1st, 7th, and 30th day treadmill exercise tests, either.

CONCLUSION

Maximal heart rates and the decline of heart rate to the 5th minute on recovery phase after treadmill exercise test have short-term reproducibility.

The effects of a 4-week coffeeberry supplementation on antioxidant status, endurance, and anaerobic performance in college athletes

The main aim of this investigation was to evaluate the changes in total antioxidant capacity (TAC) and aerobic and anaerobic performance induced by supplementation of coffeeberry (CB) formulation for 4 weeks in college athletes. Twenty college athletes (14 males and 6 females) were allocated to two randomly assigned trials. Subjects in the CB group orally ingested capsules that contained CB formulation at a dose of 800 mg per day in two equal doses for 28 days, while subjects in the placebo (P) group ingested an equal number of identical-looking caps that contained cellulose. There were no changes in glucose, cholesterol, and lipoproteins within or between trials (p > 0.05). Total antioxidant capacity (TAC) was significantly higher in the CB versus P trial at the post- supplementation trial (1.66 +/- 0.16 vs. 1.51 +/- 0.05 mmol/L; p < 0.05). There were no statistically significant changes in average anaerobic power, index of anaerobic fatigue, maximal heart rate, blood lactate, and maximal oxygen uptake within or between trials (p > 0.05). Heart rate recovery (HRR) index increased significantly in CB group as compared with baseline level (38 +/- 4 vs. 32 +/- 5 beats/min; p < 0.05). Blood lactate after 10 min of recovery (Lact(rec)) significantly decreased in the CB group after supplementation protocol as compared with initial results (7.6 +/- 4.2 vs. 5.5 +/- 2.6 mmol/L; p < 0.05). No subject reported any side effects from CB or P. The results of the present study indicate that supplementation with a CB formulation slightly increased antioxidant capacity, but there were minimal effects on recovery parameters after exercise in college athletes.

Non-invasive risk stratification: prognostic implications of exercise testing

The interpretation of exercise ECGs is frequently limited to an assessment of the ST segment for evaluation of ischemia. However, exercise testing represents a simple test of the complex interactions of the autonomous nervous system and provides a multitude of information with independent prognostic information. This overview summarizes available studies on the significance of chronotropic incompetence, exercise capacity, heart rate recovery after exercise, and the incidence of ventricular premature activity during or after exercise. These parameters express subclinical pathophysiological changes which cannot be identified by other means, e. g., coronary angiography or echocardiography. A reduced maximal heart rate under exercise may indicate a "blunted" sympathetic reaction as a protective myocardial reaction to an increase in left ventricular wall stretch in preclinical forms of heart failure. A reduced exercise capacity, measured in metabolic equivalents, METs, is one of the strongest predictors of cardiac and all cause mortality. A reduced heart rate recovery after exercise indicates an increased sympathetic tone or lack physiological increase in vagal tone; increased ventricular ectopy potentially identifies preclinical cardiomyopathy. This summary of study results aims at providing a new view on exercise testing that should lead to an improved understanding of relevant information included in the exercise ECG.

Evaluation of Autonomic Function Underlying Slow Postexercise Heart Rate Recovery

The reduction in heart rate (HR) during the first minute of recovery immediately after a graded maximal exercise stress test (GXT) has recently been found to be a powerful and independent predictor of cardiovascular and all-cause mortality. Reduced vagal activity has been postulated as the cause, but this has not been proven in a population with slow HR recovery (HRR).

PURPOSE

To investigate autonomic contributions to HRR using time-frequency analysis in a group of individuals demonstrating slow HRR.

METHODS

HRR was defined as the difference in HR between peak exercise and 1 min later; a value < or = 18 bpm was set as threshold and considered abnormal. A modified continuous wavelet transform (CWT) was used to perform time-dependent spectral analysis during the baseline steady state and the following non-steady-state conditions created by GXT. This method provides dynamic measures of low-frequency (LF) and high-frequency (HF) peaks associated with autonomic activity. Individuals (N = 20) with a previous slow HRR underwent a second GXT within 3 months after their initial test. An additional eight subjects whose first GXT disclosed normal HRR were taken as a control group.

RESULTS

Seven of 20 subjects demonstrated slow HRR (14 +/- 5 bpm) on the repeat test, and 13 subjects displayed normal HRR (29 +/- 5 bpm). Subjects with slow HRR in both GXT displayed significantly (P < 0.05) lower HF and LF fluctuations during recovery than those with normal HRR.

CONCLUSIONS

Attenuated HRR after GXT, assessed by CWT, is indeed associated with abnormal vagal reactivation and prolonged sympathetic stimulation after termination of maximal exercise.

Cardiac Rehabilitation vs. Home Exercise After Coronary Artery Bypass Graft Surgery

OBJECTIVE

The autonomic dysfunction is known to adversely affect clinical outcome in patients with cardiovascular disease, and exercise training has been shown to modify the sympathovagal control of heart rate. The purposes of this study were to investigate the effect of cardiac rehabilitation on heart rate recovery in patients who received coronary artery bypass grafting (CABG) and compare the effect with that of a home-based exercise program.

DESIGN

Fifty-four male patients having undergone CABG were randomly assigned to a cardiac rehabilitation exercise program (n = 18), a home-based exercise program (n = 18), and a control group (n = 18) for 12 wks to evaluate the differences in heart rate recovery among groups.

RESULTS

Patients in the cardiac rehabilitation group had significant increases in heart rate recovery (19.1 +/- 6.2 vs. 14.0 +/- 5.4 beats/min, P = 0.022) compared with those in the control group. There were no significant differences in heart rate recovery between cardiac rehabilitation and home-based exercise groups (16.2 +/- 4.8 beats/min) or between home-based exercise and control groups. All three groups had significantly improved heart rate recovery compared with their baseline data (P < 0.001, < 0.001, and 0.007).

CONCLUSION

Our results point out that a cardiac rehabilitation exercise program has a positive effect on heart rate recovery in patients having undergone CABG and is consistent with the autonomic improvement. Although the home-based exercise group did not reveal statistical significances over those in the control group, it had comparable efficacy to that demonstrated in the cardiac rehabilitation group.

Association of metabolic syndrome with exercise capacity and heart rate recovery in patients with coronary heart disease in the heart and soul study

It is not known whether the metabolic syndrome is associated with poor exercise capacity among patients who have established coronary heart disease. We evaluated the association of the metabolic syndrome with treadmill exercise capacity and heart rate recovery among patients who had coronary heart disease. We measured treadmill exercise capacity (METs) and heart rate recovery (beats per minute) in 943 subjects who had known coronary heart disease. Of these, 377 (40%) had the metabolic syndrome as defined by criteria of the National Cholesterol Education Program. Participants who had the metabolic syndrome were more likely to have poor exercise capacity (METs <5, 33% vs 18%, p <0.0001) and poor heart rate recovery (<or=16 beats/min, 34% vs 21%, p <0.0001) than those who did not have the metabolic syndrome. In ordinal logistic regression analyses, the metabolic syndrome was associated with decreased exercise capacity (odds ratio [OR] 2.2, 95% confidence interval [CI] 1.7 to 2.8, p <0.0001) and decreased heart rate recovery (OR 1.8, 95% CI 1.4 to 2.3, p <0.0001). These associations remained strong after adjusting for potential confounding variables (OR 1.6, 95% CI 1.2 to 2.1, p = 0.003 for decreased exercise capacity; OR 1.4, 95% CI 1.1 to 1.9, p = 0.02 for decreased heart rate recovery). The metabolic syndrome is independently associated with poor exercise capacity and poor heart rate recovery in patients who have established coronary heart disease. Decreased exercise capacity may contribute to the adverse outcomes associated with the metabolic syndrome.

Initial and Final Exercise Heart Rate Transients

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.

Heart rate recovery after exercise: a predictor of ventricular fibrillation susceptibility after myocardial infarction

Heart rate recovery after exercise, thought to be related to cardiac parasympathetic tone, has been shown to be a prognostic tool for all-cause mortality. However, the relationship between this variable and confirmed susceptibility to ventricular fibrillation (VF) has not been established. Therefore, myocardial ischemia was induced with a 2-min occlusion of the left circumflex artery during the last minute of exercise in mongrel dogs with myocardial infarction (n = 105 dogs). VF was induced in 66 animals (susceptible), whereas the remaining 39 dogs had no arrhythmias (resistant). On a previous day, ECG was recorded and a time-series analysis of heart rate variability was measured 30, 60, and 120 s after submaximal exercise (treadmill running). The heart rate recovery was significantly greater in resistant dogs than in susceptible dogs at all three times, with the most dramatic difference at the 30-s mark (change from maximum: 48.1 +/- 3.6 beats/min, resistant dogs; 31.0 +/- 2.2 beats/min, susceptible dogs). Correspondingly, indexes of parasympathetic tone increased to a significantly greater extent in resistant dogs at 30 and 60 s after exercise. These differences were eliminated by atropine pretreatment. When considered together, these data suggest that resistant animals exhibit a more rapid recovery of vagal activity after exercise than those susceptible to VF. As such, postexercise heart rate recovery may help identify patients with a high risk for VF following myocardial infarction.