Muscle sympathetic single‐unit responses during rhythmic handgrip exercise and isocapnic hypoxia in males: The role of sympathoexcitation magnitude
Bibliographic record
Abstract
A small proportion of postganglionic muscle sympathetic single units can be inhibited during sympathoexcitatory stressors in humans. However, whether these responses are dependent on the specific stressor or the level of sympathoexcitation remains unclear. We hypothesize that, when matched by sympathoexcitatory magnitude, different stressors can evoke similar proportions of inhibited single units. Multiunit and single‐unit muscle sympathetic nerve activity (MSNA) were recorded in seven healthy, young males at baseline and during: 1 ) rhythmic handgrip exercise (40% of maximum voluntary contraction) and 2 ) acute isocapnic hypoxia (partial pressure of end‐tidal O 2 of 47±3 mmHg). Single units were classified as activated, nonresponsive, or inhibited if the spike frequency was above, within, or below the baseline variability, respectively. By design, rhythmic handgrip and isocapnic hypoxia similarly increased multiunit total MSNA (delta 273±208 vs. 254±193 AU, P =0.84) and single‐unit spike frequency (delta 7±9 vs. 11±15 spikes/min, P =0.29). Among 19 identified single units, the proportion of activated (58% vs. 74%) non‐responsive (21% vs. 16%) and inhibited (21% vs. 10%) single units were not different between rhythmic handgrip and isocapnic hypoxia ( P =0.57). However, only 9 (47%) single units behaved with concordant response patterns across both stressors (8 activated and 1 non‐responsive during both stressors). During the 1‐min epoch with the highest increase in total MSNA during hypoxia (delta 595±282 AU, P <0.01) none of the single units were inhibited. These findings suggest that the proportion of muscle sympathetic single units inhibited during stress are associated with the level of sympathoexcitation and not the stressor per se in healthy young 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".