INFLUENCE OF POSTURAL POSITION ON CARDIAC OUTPUT DURING INCREMENTAL EXERCISE IN ENDURANCE-TRAINED ATHLETES
Bibliographic record
Abstract
Background: Recent evidence indicates that the stroke volume of endurance-trained athletes may continue to increase throughout incremental to maximum exercise in the upright position. However, little is known about the effects of changes in postural position on cardiac function during incremental exercise in endurance-trained cyclists. Objective: To evaluate the effects of changes in postural position on cardiac function during incremental exercise in endurance-trained athletes. Methods: The cardiovascular function of 10 endurance-trained cyclists (Age = 26 ± 5 (SD) yr, VO2max = 68 ± 4 mL/kg/min) was evaluated during incremental exercise in the supine and upright positions (counterbalanced) using radionuclide ventriculography. Results: The athletes were able to increase their stroke volume during incremental to maximal exercise in both the upright and supine positions, in the face of a reduced time for diastolic filling. The percent changes in end-diastolic volume and stroke volume were greater in the upright position versus the supine position (P < 0.05). The increase in cardiac output throughout incremental exercise in both postural positions was related to changes in heart rate, myocardial contractility and the use of the Frank-Starling mechanism. Forward stepwise regression revealed that heart rate and end-diastolic volume were the strongest predictors of cardiac output throughout incremental exercise in both postural positions. Postural position had a large influence on the impact heart rate and end-diastolic volume had on cardiac output. In the supine position, heart rate and end-diastolic volume explained 63 and 33%, respectively, of the variance in cardiac output during incremental exercise. In the upright position, heart rate and end-diastolic volume explained 27 and 68%, respectively, of the variance in cardiac output during incremental exercise. Conclusions: Highly trained endurance athletes make use of the Frank-Starling mechanism throughout incremental to maximal exercise in the supine and upright positions. Postural position has a significant effect on the relative contribution of heart rate, myocardial contractility, and the Frank-Starling mechanism to the increase in cardiac output during exercise conditions. The relative changes in end-diastolic volume and stroke volume are limited during supine exercise in comparison to upright exercise perhaps owing to the impact of the pericardium on ventricular filling.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".