Two exercise tests were performed with an intervening rest period of 45 minutes in a group of 13 subjects with previously identified exercise-induced ventricular arrhythmias and no resting arrhythmias. Both normal subjects and patients with heart disease were included in the group. The level of stresss was equal in both tests as judged by similar rate-pressure products at peak exercise. There was a significant decrease (P less than 0.05) in the number of VPCs induced by exercise during and after the second test. When the number of VPCs on test I and test II in the same patients were compared, a regression line fitted the data well (r = 0.92). Analysis of the recovery periods revealed significant (P less than 0.01) decreases in systolic blood pressure at one and three minutes post exercise, comparing the second to the first test. The underlying mechanism may be decreased myocardial oxygen demand during the second test as the lowered rate-pressure products during recovery (P less than 0.01) reflect. The results of this study indicate that tests of effectiveness of an antiarrhythmic drug should not be based solely on a decrease in the amount of severity of ventricular irritability between two successive exercise tests, one immediately before and the other following administration of the drug.
Introduction: Nocturnal blood pressure (BP) dipping determined from 24-hour ambulatory blood pressure monitoring (ABPM) is associated with reduced cardiovascular disease (CVD) risk. Physical activity lowers the risk of CVD related, in part, to preserved endothelial function and lower aortic stiffness, however the relation between physical activity and nocturnal dipping remains unclear. The objective of our cross-sectional retrospective analysis was to assess the relation between physical activity and nocturnal BP dipping, and whether this relation was confounded by measures of vascular function. We hypothesized that higher levels of physical activity would be associated with greater nocturnal BP dipping. Methods: Healthy adults (n=172, age 19 to 65 years, 55% female) had 24-hour ABPM measured. BP recordings were taken every 30 min during the daytime and every 60 min during the nighttime. Nocturnal “dippers” had a 10-20% difference between their mean daytime and nighttime systolic BP and “non-dippers/inverse dippers” had <10% difference. The modifiable activity questionnaire was used to assess physical activity levels via self-reported days/week with greater than 30 min of moderate activity (3.0-6.0 METs) and vigorous activity (>6.0 METs). Endothelial function (brachial artery flow-mediated dilation, FMD), and aortic stiffness (carotid-femoral pulse wave velocity, cfPWV) were also assessed. Results: Nocturnal BP dippers performed more days/week of moderate and vigorous physical activity compared to non-dippers (P=0.007 and P=0.008, respectively). Both moderate (B=0.386, P=0.042) and vigorous physical activity (B=0.604, P=0.002) were associated with nocturnal BP dipping in univariate linear regression analyses. However, only vigorous activity (B=0.926, P=0.001) remained associated with nocturnal BP dipping after adjustment for age, BMI, 24-hr systolic BP and diastolic BP, brachial FMD and cfPWV. Conclusion: Vigorous physical activity may attenuate CVD risk in part from enhanced nocturnal BP dipping. Future studies should investigate additional mechanisms by which vigorous physical activity may enhance nocturnal BP dipping. This study was supported by grants from the National Institutes of Health (AG063790; HL014388, HL07121; AG043722). Dr. Pierce is supported by the Russell B. Day and Florence D. Day Endowed Chair in Liberal Arts and Sciences, University of Iowa. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
6 clinically normal subjects underwent a 3-month physical conditioning program with ejection fractions determined before and after physical conditioning using a scintillation probe. All subjects achieved a conditioning effect as evidenced by increased treadmill test duration after conditioning (mean duration before conditioning: 658 vs. 715 sec after conditioning; p < 0.02). All 6 subjects increased resting ejection fractions after conditioning (mean ejection fraction before conditioning: 54.5 ± 5.4%; mean ejection fraction after conditioning: 67.0 ± 9.0%; p < 0.01). Thus, an aerobic physical conditioning program appears to increase resting ejection fractions in normal subjects.
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