Biological Sex Modestly Influences the Impact of Long Duration Bed Rest on Human Sympathetic Neurocirculatory Regulation
Bibliographic record
Abstract
Our understanding regarding the impact of simulated microgravity on sympathetic neurocirculatory regulation, and the modulatory effects of biological sex, remain incomplete. Through retrospective analysis of two long-duration bed rest trials, this study investigated the impact of 60 days of -6° head-down bed rest (HDBR) on the transduction of integrated muscle sympathetic nerve activity (MSNA; peroneal microneurography) into mean arterial pressure (MAP; Finometer) in healthy females ( n = 12, 25-40 years) and males ( n = 13, 21-42 years). Signal averaging quantified sympathetic transduction for 12 cardiac cycles (ECG) following integrated MSNA bursts. The transduction of integrated MSNA bursting patterns was studied based on the overall response, temporal burst firing patterns (singlet, doublet, and triplet+), and burst amplitude (binned into quartiles: Q1-Q4). Data are reported as mean (SD) for a 5-minute baseline period pre-HDBR and post-HDBR. Statistical analysis included mixed-effect analyses with post-hoc t-tests. In the pooled analyses, HDBR reduced the overall MAP transduction response to integrated MSNA bursts (pre-HDBR: 1.4 ± 0.5 mmHg, post-HDBR: 1.1 ± 0.4 mmHg; P = 0.003). This stemmed from attenuated MAP transduction responses to small- and medium-sized bursts (i.e., Q1-Q3) but there was no effect of HDBR on the largest bursts (i.e., Q4: pre-HDBR: 2.2 ± 0.9 mmHg, post-HDBR: 2.1 ± 0.9 mmHg; P = 0.59). HDBR did not affect the transduction response to singlets (P = 0.23), but HDBR reduced the MAP transduction responses to doublets and triplets+ (both P < 0.03). HDBR did not affect the reduction in MAP during non-bursting periods (pre-HDBR: -0.5 ± 0.2 mmHg, post-HDBR: -0.4 ± 0.2 mmHg; P = 0.17). When stratifying the analyses by sex, we observed that HDBR reduced the overall MAP transduction response to integrated MSNA bursts more so in males (P < 0.01) than females (P = 0.14). Conversely, HDBR did not affect the MAP reductions following non-bursting periods in males (P = 0.53), but in females the reduction in MAP following non-bursting periods was less after HDBR, particularly for cardiac cycles 5 to 7 (pre-HDBR: -0.8 ± 0.5 mmHg, post-HDBR: -0.5 ± 0.3 mmHg; P = 0.03). These data suggest that 60 days of HDBR attenuates sympathetic neurocirculatory regulation during baseline conditions, with a modest influence of biological sex. This work was supported by the Canadian Space Agency, Centre National d'Etudes Spatiales, European Space Agency, National Aeronautics and Space Administration, Institute of Aerospace Medicine of the German Aerospace Center (DLR), Fond Européen de Développement Régional (FEDER) and the Natural Sciences and Engineering Research Council of Canada (NSERC). This is the full abstract presented at the American Physiology Summit 2024 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.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.000 | 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 teacher head, 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".