Long Duration Bed Rest Modifies Cardiovagal Baroreflex Control but not Baroreflex Control of Muscle Sympathetic Action Potential Activity in Humans
Bibliographic record
Abstract
Our understanding of altered neuro‐cardiovascular control following long‐duration inactivity via head‐down bed rest (HDBR) is incomplete. Here, we retrospectively analyzed two long‐duration HDBR studies, including female (n=17; 32±5 years) and male (n=16; 29±7 years) cohorts, to determine whether HDBR 1) alters spontaneous cardiovagal baroreflex sensitivity (cBRS) similarly between males and females and 2) alters spontaneous baroreflex control of muscle sympathetic action potentials (AP) in males. Heart rate (HR; electrocardiogram) and arterial blood pressure (BP; finger‐plethysmography) were continuously measured during 5‐minutes of supine rest prior to and following 60‐days bed rest in a ‐6° head‐down position. Spontaneous cBRS was assessed by the relationship between R‐R interval and systolic BP analyzed using the linear regression sequence method. Recordings of multi‐unit muscle sympathetic nerve activity (peroneal microneurography) were obtained and a continuous wavelet transform detected APs which were grouped into AP clusters with similar morphology (n=10, all males). Baroreflex threshold for AP cluster discharge was assessed by linear regression analysis of the relationship between AP cluster discharge probability and diastolic BP. No change in resting HR (64±9 versus 66±9 /min, P=0.12) or mean BP (91.2±9.0 versus 90.6±9.2 mmHg, P=0.73) occurred after HDBR. Reductions in cBRS after HDBR (‐4.1±9.4 ms/mmHg, Time effect: P<0.01) were similar between males and females (Time‐by‐Sex effect: P=0.51) and not related to changes in total blood volume (r 2 =0.045, P=0.24). Grouped AP clusters demonstrated heterogenous arterial baroreflex threshold gain according to AP cluster morphology (Cluster effect: P<0.01) which was unaltered following HDBR (Time‐by‐Cluster effect: P=0.43). In summary, males and females similarly attenuate cBRS following 60‐days of HDBR and novel evidence indicates HDBR does not alter spontaneous baroreflex control of muscle sympathetic APs in males.
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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".