Orthostatic cardiovascular responses to postural sway and discreet counterpressure maneuvers
Bibliographic record
Abstract
Counterpressure maneuvers (CPM) are movements used to delay or abort syncope, but may have practical barriers to use. We recently showed exaggerated postural sway produces protective responses against syncope. Accordingly, we aimed to evaluate a series of discreet, accessible movements as novel preventative CPM. We tested 26 healthy adults (12 female) aged 28.9 ± 1.2 years. Participants performed a baseline stand (BL), followed by three randomized CPM trials (exaggerated anteroposterior sway, AP; toe clenching, TC; gluteal muscle clenching, GC). Non-invasive beat-to-beat systolic arterial pressure (SAP), heart rate, stroke volume (SV), cardiac output (CO), total peripheral resistance (TPR), mean middle cerebral artery blood velocity (mMCAv), and total path length moved (TPL) were measured. Muscularity was assessed using bioelectrical impedance. All discreet CPM augmented orthostatic SV (p < 0.001) and CO (p < 0.001), while reducing TPR (p < 0.001). SAP increased during AP (p < 0.001) and GC (p < 0.001), but not TC. GC responses were unstable, with increased standard deviation of SAP (p = 0.002) and SV (p = 0.022) that may predispose syncope. Only AP improved mMCAv (p = 0.005) and sympathovagal balance (p < 0.001). Responses were largest in those with greater initial cardiovascular instability (p < 0.003), larger leg muscle mass (p < 0.02), and where TPL was greater (p < 0.002). These novel CPM hold clinical potential for the prevention of orthostatic syncope and presyncope, while addressing real-world patient-reported barriers to CPM. Exaggerated AP sway was most robust and stable at improving orthostatic hemodynamics in healthy controls, with reduced reliance on sympathetic baroreflex-mediated vasoconstriction during enhanced muscle pumping activity. Accordingly, AP shows the most promise as a simple and discrete CPM.
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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 | 0.006 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".