In vivo assessment of blood pooling and muscle pump dynamics under orthostatic stress
Bibliographic record
Abstract
A better understanding of blood pooling to the lower limbs and muscle pumping (increasing venous return) is essential to prevent orthostatic intolerance. The goal of this study is to assess the dynamics of these physiological responses under orthostatic stress. Repeated 70 degrees Head Up Tilt (HUT) of 3 minutes were performed on a group of 15 healthy volunteers. After 1st and 2nd minute of HUT, the subjects performed a 3 s calf Muscle Contraction (MC) at 30% of maximal electromyographic activity. Calf muscles EMG, ECG and finger blood pressure were recorded continuously. Blood volume flow (BVF) of the femoral artery was assessed with ultrasound from 1 min before to 1 min after HUT. A peak BVF of 620 mL/min was measured after HUT, whereas peak BVF after MC reached 950 mL/min. Plateau BVF in the femoral artery during HUT increased slightly after the MC possibly due to a metabolic response of the leg muscle. Finally, mean arterial pressure immediately after tilting and after MC decreased. We therefore conclude that the muscle pump through its effect on venous pressure of the lower limbs is a fundamental aspect in blood pressure regulation during orthostatic stress.
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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 | 0.000 |
| 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".