Submaximal Heart Rate Response Research Articles

Contrasts in intermittent endurance performance and heart rate response between female and male soccer players of different playing levels.

This study compared intermittent endurance performance and heart rate (HR) response, as well as their relationship, by sex and competitive level in soccer. A total of 68 outfield (18 elite and 16 sub-elite female, 17 elite and 17 sub-elite male) soccer players performed the Interval Shuttle Run Test (ISRT) with monitored HR. Sex and level effects were evaluated by two-way analysis of variance (ANOVA) and the relationships between parameters using Pearson’s correlation coefficient. Female players presented lower performance (effect sizes [ES]: 2.12-4.71, p < 0.01) and higher submaximal HR during the ISRT (ES: 1.66-3.40, p < 0.01). Elite players showed higher performance and reduced submaximal HR compared with their sub-elite counterparts, with a large level effect only evident between the female groups (ES: 1.22-1.56, p < 0.01). The maximum and the HR recovery 1 min after the ISRT (HRR) did not differ among all groups (ES: 0.01-0.51, p ≥ 0.18). The HRR was slightly related to the test performance for all groups (r = 0.20, p = 0.12). Large to very large negative correlations were verified between HR at 6 and 9 min during the ISRT and the test performance for each group (r = -0.54 to -0.84, p ≤ 0.04). However, 16 (3 elite and 13 sub-elite) female players did not reach the 9th minute of the test. The gap between competitive levels among female soccer players is greater than that observed for male players in intermittent endurance performance and submaximal HR response. The HRR had only a minor impact on performance and was influenced neither by sex nor by level.

Dobutamine stress echocardiography during follow-up surveillance in heart transplant patients: Diagnostic accuracy and predictors of outcomes

Cardiac allograft vasculopathy (CAV), a major cause of graft failure and mortality at >3 years after orthotopic heart transplantation (OHT), is commonly evaluated using dobutamine stress echocardiography (DSE). We sought to study: (a) the incidence of positive results and diagnostic accuracy of DSE; and (b) the predictors of adverse outcomes in OHT patients. We studied 497 consecutive patients (63 ± 10 years, 78% men) with OHT who had undergone DSE as part of routine surveillance at our center between 1998 and 2013. Every DSE and coronary angiogram performed during follow-up was reviewed. CAV was regraded according to the 2010 recommendations of the International Society for Heart and Lung Transplantation. Composite events (death, coronary revascularization, myocardial infarction and retransplantation) were recorded. There were 1,243 DSE studies performed during a median of 8.7 (6.2 to 11.9) years after transplantation. Only 22 studies (1.8%) were positive, 978 (78.7%) were negative and 243 (19.5%) were non-diagnostic (sub-maximal heart rate response) for ischemia. Among 497 patients, only 20 (4%) had at least one positive DSE study. There were 310 diagnostic DSEs with coronary angiograms performed within 1 year of one another other. In this subgroup, the sensitivity, specificity, positive predictive value and negative predictive value of DSE were 7%, 98%, 82% and 41%, respectively, to detect any CAV, and 28%, 98%, 71% and 89% to detect CAV Grades 2 or 3, respectively. There were no deaths during DSE. At 5.6 ± 3.6 years after DSE, there were 201 (40%) events. Degree of CAV (and not DSE-based ischemia, p = 0.3) independently predicted outcomes (p < 0.001). The incidence of a positive result is very low in OHT patients undergoing surveillance DSE. DSE is insufficiently sensitive for detection of early CAV. Degree of CAV and not DSE-based ischemia independently predicted outcomes.

Abnormal left ventricular contractile response to exercise in the absence of obstructive coronary artery disease is associated with resting left ventricular long-axis dysfunction.

The etiology of reduced left ventricular (LV) ejection fraction after exercise, without obstructive coronary artery disease or other established causes, is unclear. The aims of this study were to determine whether patients undergoing treadmill stress echocardiography with this abnormal LV contractile response to exercise (LVCRE) without established causes have resting LV long-axis dysfunction or microvascular dysfunction and to determine associations with this abnormal LVCRE. Of 5,275 consecutive patients undergoing treadmill stress echocardiography, 1,134 underwent cardiac computed tomography angiography or invasive angiography. Having excluded patients with obstructive coronary artery disease, hypertensive response, submaximal heart rate response, resting LV ejection fraction < 50%, and valvular disease, 110 with "abnormal LVCRE" and 212 with "normal LVCRE" were analyzed. Resting mitral annular velocities were measured to assess LV long-axis function. Myocardial blush grade and corrected Thrombolysis In Myocardial Infarction frame count were determined angiographically to assess microvascular function. Comparing normal LVCRE with abnormal LVCRE, age (mean, 59.7 ± 11.1 vs 61.4 ± 10.0 years), hypertension (53% vs 55%), diabetes (16% vs 20%), and body mass index (mean, 29.1 ± 5.4 vs 29.5 ± 6.4 kg/m(2)) were similar (P > .05). Abnormal LVCRE had reduced resting LV long-axis function with lower septal (mean, 6.1 ± 1.9 vs 7.7 ± 2.2 cm/sec) and lateral (mean, 8.1 ± 2.9 vs 10.4 ± 3.0 cm/sec) e' velocities (P < .001) and larger resting left atrial volumes (mean, 37.3 ± 10.1 vs 31.1 ± 7.2 mL/m(2), P < .001). On multivariate analysis, female gender (odds ratio [OR], 1.21; 95% confidence interval [CI], 1.15-1.99; P < .001), exaggerated chronotropic response (OR, 1.49; 95% CI, 1.09-2.05; P < .001), resting left atrial volume (OR, 2.38; 95% CI, 1.63-3.47; P < .001), and resting lateral e' velocity (OR, 1.70; 95% CI, 1.22-2.49; P = .003) were associated with abnormal LVCRE, but not myocardial blush grade or corrected Thrombolysis In Myocardial Infarction frame count. An abnormal LVCRE in the absence of established causes is associated with resting LV long-axis dysfunction and is usually seen in women.

Abstract 9333: Prognostic Value of Stress Echocardiography In Patients Achieving a High Exercise Workload (=10 Metabolic Equivalents) and Submaximal Heart Rate Response

Background: High exercise capacity (≥10 metabolic equivalents, METS) is a predictor of favorable prognosis. Submaximal studies (&lt;85% maximum predicted heart rate, MPHR) may lead to non-diagnostic results and indeterminate outcomes. The purpose of this study was to examine the prognostic value of stress echocardiography (SEcho) in patients achieving high exercise capacity and submaximal heart rate response. Methods: We evaluated 81 patients (50 ± 13 years; 62% male) achieving nine minutes (≥10 METS) and &lt;85% MPHR with treadmill SEcho. Resting left ventricular ejection fraction and regional wall motion were assessed. The left ventricle was divided into 16 segments and scored on 5-point scale of wall motion. Abnormal SEcho was defined as stress-induced ischemia (wall-motion score of ≥1 grade). Followup (3.4 ± 1.5 years) for non-fatal myocardial infarction and cardiac death (n = 2) were obtained. Results: By univariate analysis, the number of new ischemic wall motion abnormalities (hazard ratio = 2.5, confidence interval 1.2 - 5.3, p = 0.02) was the most significant predictor of cardiac events. Cumulative survival in patients achieving nine minutes (≥10 METS) and &lt;85% MPHR was significantly worse in patients with abnormal (ischemic) vs. normal (nonischemic) SEcho (1.1%/year vs. 0.2%/year, p = 0.02)[Graph]. Conclusions: The ability to achieve nine minutes (≥10 METS), despite &lt;85% MPHR by treadmill SEcho was associated with a benign prognosis (~1.0%/year). In the setting of high achieved exercise capacity and &lt;85% MPHR, SEcho results (presence or absence of ischemia) were further able to sub-stratify this low risk group.

Diagnostic value of dobutamine stress Doppler tissue imaging in diabetic patients with suspected coronary artery disease

Coronary artery disease (CAD) is often silent in diabetic patients, and it is typically in advanced stages of development by the time it manifests. Various forms of stress testing have been investigated to detect obstructive CAD in diabetes mellitus. To assess the diagnostic value of dobutamine stress pulsed-wave Doppler tissue imaging (DTI) compared with standard wall motion analysis in detection of myocardial ischemia in diabetic patients with suspected CAD. The study comprised 46 diabetic patients with suspected CAD who underwent dobutamine stress echocardiography (DSE) with DTI within 4 weeks before coronary angiography (CA). Dobutamine infusion started at 5 μ/kg/min and increased up to 40 μ/kg/min with additional atropine during submaximal heart rate responses. In addition to wall-motion score index (WMSI) analysis, pulsed-wave DTI examination of basal and mid segments of posteroseptal, lateral, anterior, inferior and anteroseptal walls was performed. Myocardial velocities were measured at rest in the apical 4, 3 and 2-chamber views. The measurements were repeated at low dose (10–15 μ/kg/min) and at peak stress (40 μ/kg/min). DTI measurements included peak systolic velocity ( S ), peak early diastolic velocity ( E ) and peak late diastolic velocity ( A ) and the results were compared to WMSI analysis. Patients were classified into two groups according to CA results; group (I) diabetics with positive CA ( n = 27) and group (II) diabetics with negative CA ( n = 19). There was no significant difference between the two groups in duration of diabetes, global WMSI at rest or the Δ changes (stress-rest/rest) of WMSI ( p > .05). Global S and global E were significantly lower in group I compared to group II at peak stress (11.3 ± 3.7 cm/s vs. 14.5 ± 2.2 cm/s, p < 0.01) and (11.3 ± 1.6 cm/s vs. 13.1 ± 2.1 cm/s, p < 0.01) respectively. The cutoff points for global S and global E to detect obstructive CAD in diabetics were 11.3 cm/s and 11.2 cm/s respectively with 75.7%, 73.4% sensitivity and 94.7%, 89.47% specificity respectively. An increment (Δ changes) less than 0.56 in S or 0.26 in E from rest to peak stress identified CAD with 78.8%, 89.3% sensitivity and 94.7%, 90.7% specificity respectively. The accuracy of DTI parameters during peak stress was higher than WMSI analysis (sensitivity 74.1% vs. 59.3% and specificity 90% vs. 79%, p < 0.01 for each). In multivariate regression analysis, only Δ S and Δ E were independent predictors of obstructive CAD in diabetics (odd ratio: 36.16, 95% CI, 1.34–532.01 and 63.77, 95% CI, 3.19–721.47) respectively. Quantitative analysis, using DTI during DSE, adds new dimension in diagnosis of myocardial ischemia. It is more sensitive, specific, accurate and reproducible compared with standard wall motion analysis for recognition of significant CAD in diabetic patients.

Diagnostic value of dobutamine stress Doppler tissue imaging in diabetic patients with suspected coronary artery disease

Background: Coronary artery disease (CAD) is often silent in diabetic patients, and it is typically in ad-vanced stages of development by the time it manifests. Various forms of stress testing have been investigated to detect obstructive CAD in diabetes mellitus. Ob-jectives: To assess the diagnostic value of dobutamine stress pulsed-wave Doppler tissue imaging (DTI) compared with standard wall motion analysis in de-tection of myocardial ischemia in diabetic patients with suspected CAD. Methods: The study comprised 46 diabetic patients with suspected CAD underwent dobutamine stress echocardiography (DSE) with DTI within 4 weeks before coronary angiography(CA). Dobutamine infusion started at 5 µ/kg/min and in-creased up to 40 µ/kg/min with additional atropine during submaximal heart rate responses. In addition to wall-motion score index (WMSI) analysis, pulsed- wave DTI examination of basal and mid segments of posteroseptal, lateral, anterior, inferior and antero- septal walls was performed. Myocardial velocities were measured at rest in the apical 4, 3 and 2-cham- ber views. The measurements were repeated at low dose (10 - 15 µ/kg/min) and at peak stress (40 µ/kg/min). DTI measurements included peak systolic velocity (S), peak early diastolic velocity (E) and peak late diastolic velocity (A) and the results were com-pared to WMSI analysis. Patients were classified into two groups according to CA results; group (I) di-abetics with positive CA (n = 27) and group (II) di-abetics with negative CA (n = 19). Results: There was no significant difference between the two groups in duration of diabetes, global WMSI at rest or the ? changes (stress-rest/rest) of WMSI (P > 0.05). Global S and global E were significantly lower in group I compared to group II at peak stress (11.3 ± 3.7 cm/sec vs. 14.5 ± 2.2 cm/sec, p < 0.01) and (11.3 ± 1.6 cm/sec vs. 13.1 ± 2.1 cm/sec, p < 0.01) respectively. The cutoff points for global S and global E to detect obstructive CAD in diabetics were 11.3 cm/s and 11.2 cm/s re-spectively with 75.7%, 73.4% sensitivity and 94.7%, 89.47% specificity respectively. An increment (? changes) less than 0.56 in S or 0.26 in E from rest to peak stress identified CAD with 78.8 %, 89.3% sensi-tivity and 94.7%, 90.7% specificity respectively. The accuracy of DTI parameters during peak stress was higher than WMSI analysis (sensitivity 74.1% vs. 59.3% and specificity 90% vs. 79%, P < 0.01 for each). In multivariate regression analysis, only ?S and ?E were independent predictors of obstructive CAD in diabetics (odd ratio: 36.16, 95% CI, 1.34- 532.01 and 63.77, 95% CI, 3.19-721.47) respectively. Conclusion: Quantitative analysis, using DTI during DSE, adds new dimension in diagnosis of myocardial ischemia. It is more sensitive, specific, accurate and reproducible compared with standard wall motion analysis for recognition of significant CAD in diabetic patients.

Tissue Velocity Imaging with Dobutamine Stress Echocardiography–A Quantitative Technique for Identification of Coronary Artery Disease in Patients with Left Bundle Branch Block

Patients with left bundle branch block (LBBB) exhibit abnormal septal motion that may limit the interpretation of stress echocardiograms and persuade the results of myocardial scintigraphy. We sought to analyze whether the use of tissue velocity imaging during graded dobutamine infusion is useful to identify and predict coronary artery disease (CAD) in patients with complete LBBB. In all, 62 patients with LBBB (mean age 62 years, 34 men) with suggested CAD underwent dobutamine stress-tissue Doppler echocardiography within 6 weeks before coronary arteriography. Dobutamine infusion started at 5 micro/kg/min and increased up to 40 micro/kg/min with additional atropine during submaximal heart rate responses. In addition to wall-motion analysis, pulsed wave tissue Doppler sampling of mitral annulus at 5 corners was performed at rest in the apical 4-chamber plus aorta and 2-chamber apical views. The measurements were repeated at low dose (10-15 micro/kg/min) and at peak stress. Tissue Doppler echocardiography measurements included early peak systolic velocity (PSV), postsystolic shortening (PSS) velocity, peak early diastolic velocity (Ve), and peak late diastolic velocity. The results were compared with 20 healthy subjects as a control group. Patients were classified into two groups according to angiographic results: LBBB with CAD (n = 32) and LBBB without CAD (n = 30). There was no significant difference between LBBB groups in global wall-motion score index at rest; the delta changes in each group were almost similar during peak stress test (P > .05). In the LBBB with CAD group, PSV increased during peak stress to a smaller extent (6.3 +/- 1.1-7.2 +/- 2.0 cm/s, approximately 24% P < .03) than in non-CAD group (6.8 +/- 1.0-9.6 +/- 2.7 cm/s, approximately 46% P < .01). Similarly, Ve increased to a lesser extent in CAD group (deltaVe 1.6 +/- 1.7 vs 2.8 +/- 1.7 cm/s, approximately 25% vs 42% P < .0001). There were no significant difference in delta late diastolic velocity between LBBB and control groups or between each of them. PSS could be recorded at rest in 24 of 32 patients (75%) in CAD group and 17 of 30 patients (57%) in non-CAD group. In LBBB with CAD group, PSS was developed and significantly augmented from 4.7 +/- 3.1 to 6.3 +/- 3.4 cm/s (P < .001) during stress. Increment less than 2.5 cm/s in PSV and Ve during peak stress identified CAD with 88% sensitivity (for each) and 90% and 87% specificity, respectively. The cut-off values of PSS velocity greater than 4 cm/s at peak stress have strong diagnostic power for prediction of obstructive CAD in patients with LBBB (82% accuracy). Tissue Doppler echocardiography with dobutamine stress allows a diagnostic benefit in the detection of CAD in patients with LBBB. The magnitude of change of PSV and Ve in addition to PSS are quantitative parameters to identify CAD in patients with LBBB where subjective wall-motion analysis failed.

Adapting the 20 Metre Shuttle Run to a Submaximal Protocol to Predict Peak VO2

PURPOSE: The purpose of this study was (1) to compare the peak oxygen uptake (VO2peak) predicted from the Leger 20 Metre Shuttle Run test (LT) with measured VO2peak in healthy subjects, and (2) to develop prediction equations for VO2peak using body mass index and heart rate responses at submaximal intensities from the LT. METHODS: Seventeen female (mean age ± SD; 21 ± 3 yrs) and 17 male subjects (23 ± 2 yrs) completed a ramped maximal exercise treadmill test (RT), a graded maximal treadmill test (GT) and the LT with a minimum of two days rest between testing sessions. Both the RT and LT involved increases in speed every minute (i.e., stage). The GT was used to confirm VO2peak from the RT. VO2peak was determined during the RT and GT using metabolic gas analysis. The VO2peak from the LT was estimated from the prediction equations developed by Leger et al. (1988), Leger and Gadoury (1989), and Stickland et al. (2003). Data were analysed using multiple regression and ANOVA. Significance was determined when p < 0.05. RESULTS: The LT stages completed were 7.5 ± 1.5 for females and 10 ± 2.3 for males. Throughout exercise and at peak, no significant differences in heart rate were found between the RT and LT (p > 0.05). VO2peak from the RT was significantly higher than the GT for both males and females (p < 0.01). The regression equation from Leger et al. (1988) under predicted VO2peak in males and over predicted VO2peak in females (p < 0.05). The Leger and Gadoury (1989) regression equation accurately predicted VO2peak in females (p > 0.05), but under predicted VO2peak in males (p < 0.05). The regression equation of Stickland et al. (2003) over predicted VO2peak in both males and females (p < 0.05). Multiple regression analysis using body mass index (X≥0), heart rate at rest (X1), minute 1 (X2), minute 2 (X3), and minute 3 (X4) from RT and LT indicated a significant relationship for males (p < 0.05; r2 = 0.76; SEE = 3.5) and females (p < 0.05; r2 = 0.6; SEE = 2.9). The following equations were developed to predict VO2peak from submaximal LT intensities: Males = 135 + (−0.72X≥0) + (−0.17X1) + (−0.03X2) + (0.33X3) + (−0.67X4 Females = 93 + (−0.25X≥0) + (−0.11X1) + (0.14X2) + (−0.28X3) + (−0.05X4 CONCLUSION: These results indicated that most LT predictive equations under- or over-estimate VO2peak. The findings of this study also suggest that body mass index and submaximal heart rate responses from the LT may be used to predict VO2peak.

Strength and physiological response to exercise in patients with chronic fatigue syndrome

OBJECTIVETo measure strength, aerobic exercise capacity and efficiency, and functional incapacity in patients with chronic fatigue syndrome (CFS) who do not have a current psychiatric disorder.METHODSSixty six patients with CFS...

Comparison of cardiovascular adaptations to long-term arm and leg exercise in wheelchair athletes versus long-distance runners

The effect of long-term arm exercise on cardiac morphology and function is unknown. To study these effects, highly trained wheelchair athletes were compared with long-distance runners and controls. In addition, the wheelchair athletes were compared with the long-distance runners to determine if long-term leg exercise confers a training effect during the performance of dynamic arm exercise. The study included 31 male subjects (mean age of 33 ± 5 years), who comprised 3 groups matched for age and weight: wheelchair athletes (n = 9), long-distance runners (n = 12), and healthy controls (n = 10). All underwent echocardiography at rest and arm ergometry exercise testing with expiratory gas analysis. The peak work rate during arm exercise was highest among the wheelchair athletes, and was significantly higher in both groups of trained athletes compared with the control group (p <0.001). Runners demonstrated a significantly lower submaximal heart rate response to arm exercise compared with wheelchair and control subjects. Wheelchair athletes had increased left ventricular (LV) volume and mass by echocardiography compared with controls, but not to the same degree as that of runners. Although chamber dimensions and wall thickness did not differ among the groups, the LV volume index tended to be largest in the runners. Doppler indexes of diastolic LV filling were similar between the trained and untrained subjects. These data demonstrate that both long-term arm and leg exercise yield increases in LV volume and mass compared with untrained control subjects, although to a lesser degree in arm-trained athletes. Runners demonstrated a transfer of training effect in the performance of dynamic arm exercise, as demonstrated by their ability to achieve a higher peak work rate than controls, and showed a lower heart rate response to submaximal exercise than the wheelchair athletes and control subjects.

Aortic Regurgitation Reduces the Accuracy of Exercise Echocardiography for Diagnosis of Coronary Artery Disease

The association of aortic regurgitation with left ventricular size, hypertrophy, and abnormal coronary flow may influence the accuracy of stress testing techniques for the diagnosis of coronary disease. We examined the diagnostic accuracy of treadmill exercise echocardiography to predict coronary artery disease in 76 patients with moderate to severe aortic regurgitation. Rest and poststress images were interpreted by 2 experienced observers, and accuracy was defined by comparison with stenoses ≥50% diameter at coronary angiography. Results were compared with accuracy in a control group of previously published studies in patients without valvular heart disease. After 6 patients were excluded because of a submaximal heart rate response (<85% age-predicted maximal heart rate), 70 patients were included in the final analysis. Patients with aortic regurgitation were of comparable age to the control group and exercised to similar workload. In 16 (23%) patients with significant coronary artery disease and significant aortic regurgitation, the sensitivity of exercise echocardiography was 56% compared with 83% in the control group ( P = .03). The specificity in 54 patients with aortic regurgitation but no significant coronary artery disease was 67% compared with 83% in the control group ( P = .02). Accuracy was 64% in aortic regurgitation compared with 83% in the control group ( P = .02). In patients with aortic regurgitation, accuracy in the left anterior descending artery territory (76%) marginally exceeded that in the posterior (right + circumflex coronary artery) circulation (70%). Thus the presence of significant aortic regurgitation affects the regional wall motion of the left ventricle during exercise and adversely affects the accuracy of exercise echocardiography for the diagnosis of coronary artery disease. (J Am Soc Echocardiogr 1999;12:967-73.)

Influence of Gender on Physiologic Response and Accuracy of Dobutamine Echocardiography

Dobutamine echocardiography (DE) has been shown to be safe, feasible, and accurate for identification of coronary artery disease (CAD) in mixed populations. The purpose of this study was to examine gender differences in physiologic response and accuracy of DE. We studied 2,886 consecutive DEs, performed in 2,748 patients, 1,209 of whom (44%) were women. A standard incremental protocol (5 to 40 μg/kg/min in 3-minute stages) was followed by atropine and/or an additional stage with 50 μg/kg/min, if the heart rate response was inadequate. Hemodynamic and echocardiographic findings were recorded at each stage. Three hundred sixty-nine patients without previous cardiac intervention (including 135 women) also underwent cardiac catheterization within 1 year of DE. Significant coronary stenoses (defined angiographically as >50% diameter) were present in 67% of women and 65% of men, of whom 55% and 65%, respectively, had multivessel disease. Women had a higher baseline heart rate (76 ± 13 vs 73 ± 14 beats/min, p <0.0001), and showed a more rapid increase in heart rate at low dose, with a higher age-predicted maximum heart rate at peak. This led to test termination at target heart rate but a submaximum dose in 22% of women versus 15% of men (p <0.0001) and less frequent administration of atropine (29% vs 34%, p <0.01). Dose-limiting side effects (8% vs 7%) and submaximum heart rate responses (14% vs 17%) were comparable in men and women. Even after the exclusion of negative DE at submaximal heart rate responses, the overall sensitivity was significantly lower in women than men (78% vs 88%, p <0.05), both for single (72% vs 78%, p <0.05) and for multivessel disease (82% vs 93%, p <0.05). The low specificity in both genders (55% vs 46%) probably reflected post-test referral bias. Thus, physiologic responses to dobutamine stress are comparable in men and women, except for a more rapid heart rate response in women, but the accuracy of DE for diagnosis of CAD in women is less than in men.

Time course of maximal and submaximal adaptation to endurance training in women

This study observed the time course of the maximal and submaximal physiologic response of nine moderately fit women (peak oxygen consumption [VO2peak] 41.5 ± 1.6 ml.kg‐1.min‐1), 20 to 25 years of age, during 6 weeks of cycle ergometer training. Each subject completed a weekly maximum cycle ergometer exercise test and 4 days a week of training for 40 min‐day‐1 at 80 to 85% VO2peak. The Astrand‐Ryhming submaximal cycle ergometer test was used to compare the weekly change in predicted VO2max to actual VO2peak. A significant (p ≤0.05) decrease in mean submaximal heart rate response to an absolute (‐12 b.min‐1) and relative (‐8 b.min‐1) work rate was observed and there was a significant increase in mean predicted VO2max (0.47 L.min‐1) after 1 week of training. A significant increase in actual VO2peak (0.27 L.min‐1) occurred after 3 weeks of training. Correlation between the predicted and actual VO2peak values decreased significantly (p ≤0.05) after weeks 1 and 2 of training but in weeks 3 to 6 the correlation ...

Effect of prolonged running on physiological responses to subsequent exercise.

The purpose of this study was to compare metabolic and cardiopulmonary responses for submaximal and maximal exercise performed several days preceding (pre-test) and 45 min after (post-test) 21 miles of high intensity (70% VO2 max) treadmill running. Seven aerobically trained subjects' oxygen uptake, oxygen pulse, respiratory exchange ratio, heart rate, pulmonary ventilation, ventilatory equivalent of oxygen, and blood lactate concentration were determined for exercise during the pre- and post-test sessions. No differences were found for submaximal oxygen uptake, oxygen pulse, pulmonary ventilation and ventilatory equivalent of oxygen between the pre- and post-test values. Generally, submaximal heart rate responses were higher, and respiratory exchange ratio values were lower during the post-test. Reductions of maximal work time (12%), maximal oxygen uptake (6%) and maximal blood lactate concentration (47%) were found during the post-test. Thermal stress and glycogen depletion are possible mechanisms which may be responsible for these observed differences.

Reduced heart rate response to exercise in ischemic heart disease

When exercise testing 159 patients with prior myocardial infarction, we identified 39 who were limited by fatigue. This group was all in sinus rhythm; none were taking drugs likely to impair the chronotropic response of the heart; none experienced chest pain or developed ischemic ECG changes. In 18 of this group, maximal heart rate achieved with exercise was 2SD or more below the age predicted value, and their heart rate response to exercise was reduced compared to that of the other 21 whose maximal exercise heart rates were within 2SD of age predicted values. A subgroup of 8 subjects with reduced exercise heart rates was studied before and after vagal blockade. In the 4 subjects whose infarction was inferior, the reduction in heart rate response was more profound and persisted after vagal blockade, suggesting either reduced pacemaker responsivness, due to ischemia or infarction, or autonomic imbalance as possible mechanisms. All 8 showed alinear increases in ventilation at higher power outputs and mean blood lactate postexercise was 7.5 mM/I without vagal blockade. Our findings suggest that a reduced heart rate response to exercise, already shown to imply added coronary risk, may be subdivided aetiologically and possibly prognostically. The use of a "Target Heart Rate" in such patients offers no safety margin, and maximal exercise capacity will be grossly over-estimated if extrapolated from the submaximal heart rate response. A cardiovascular limitation to exercise may be detected by an alinear increase in ventilation.

THE INTERPLAY BETWEEN PERIPHERAL AND CENTRAL FACTORS IN THE ADAPTIVE RESPONSE TO EXERCISE AND TRAINING

(1) Local adaptation of skeletal muscles (fibers) only occurs in the extremity involved in the training. (2) Work performance and maximal oxygen uptake were significantly increased only in the trained leg, and the "transfer" to the untrained leg was very small. (3) The classical sign of a training effect with a lowered submaximal heart rate response could only be elicited when exercising the trained leg. Lactate concentration and release of lactate were also lower when the trained leg performed the exercise. (4) The present results suggest that the local adaptation of skeletal muscle to training is of primary importance for enhancing work capacity and oxygen uptake. (5) The results also indicate that there may exist a peripheral factor in the regulation of the heart rate response during exercise. Moreover, the data favor the hypothesis of a chemical receptor playing a role in such a peripheral control system.