Effects of Blood Withdrawal on Cardiac, Hemodynamic, and Pulmonary Responses to a Moderate Acute Workload in Healthy Middle‐Aged and Older Females
Bibliographic record
Abstract
Background The fundamental role of blood volume (BV) on cardiorespiratory fitness has been well studied in males during maximal exercise. However, understanding the importance of BV on key physiological responses to a submaximal workload in females has yet to be elucidated. The objective of this study was to investigate the effects of blood withdrawal on cardiac, hemodynamic, and pulmonary responses to submaximal exercise in females. We hypothesized that blood withdrawal would reduce cardiac filling and stroke volume (SV) which would result in a compensatory increase in heart rate (HR) to preserve cardiac output (Q) at a fixed submaximal workload. Methods 30 healthy females (63.8 ± 8.3 yr) were recruited for this study. Transthoracic echocardiography, non‐invasive blood pressure monitoring, and a peak oxygen uptake (VO 2peak ) test were performed at a 100 W submaximal workload prior to and immediately after a 10 % reduction of BV. Primary outcomes included left ventricular end‐diastolic volume (LVEDV), SV, Q, HR, and VO 2peak . BV was determined using an established carbon monoxide rebreathing technique. Results BV of subjects ranged from 3.8 to 6.6 L, with an average 10 % reduction of 0.5 ± 0.1 L. Following blood withdrawal, both LVEDV ( P ≤ 0.030) and SV ( P < 0.019) were reduced while Q was unchanged ( P = 0.139) due to an augmented HR ( P < 0.026). Submaximal hemodynamic variables including MAP ( P < 0.015), SBP ( P < 0.005), and DBP ( P < 0.038) were reduced while VO 2peak was unaltered ( P = 0.250). Conclusion Blood withdrawal results in marked reductions in cardiac filling with compensatory chronotropic responses that preserve Q at an acute moderate submaximal workload in healthy females. BV thus determines the relative exercise intensity, as typically determined by HR, of submaximal efforts in this population.
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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".