Near‐infrared spectroscopy provides an index of blood flow and vasoconstriction in calf skeletal muscle during lower body negative pressure
Bibliographic record
Abstract
AIM: Near-infrared spectroscopy (NIRS) has been used previously for forearm blood flow estimation at rest and during exercise. In this study we applied NIRS to selectively monitor deep calf oxygenated haemoglobin (Hb) responses in order to estimate blood flow changes in the calf muscle during lower body negative pressure (LBNP). The purpose of this study was to test the hypothesis that changes in calf skeletal muscle oxygenated-Hb, after the removal of superficial tissue responses, were related to blood flow changes during orthostatic stress, and to determine the efficacy of using NIRS measurements as an index of vasoconstriction. METHODS: Twenty-nine subjects participated in this study. All attempted a graded LBNP trial from baseline (0 mmHg) to -60 mmHg LBNP in 10 mmHg steps at 5-min intervals. Calf blood flow changes were estimated by oxygenated-Hb responses in relation to changes in mercury strain gauge plethysmography and muscle sympathetic nerve activity (MSNA). RESULTS: Calf selective deep oxygenated-Hb decreased continuously from -10 mmHg LBNP. Regression analysis showed that oxygenated-Hb was significantly related to declines in plethysmography evaluations of blood flow [oxygenated-Hb = (-1.57 +/- 0.26) + (1.86 +/- 0.49) plethysmography, r(2) = 0.87 +/- 0.09]. Changes in MSNA (total activity) were also inversely related to oxygenated-Hb (slope < 0, P = 0.037; r(2) = 0.52 +/- 0.15). CONCLUSION: These results suggest that changes in selective deep calf oxygenated-Hb can be utilized to estimate calf muscle blood flow changes that are most likely caused by vasoconstriction during graded LBNP.
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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) | 0.001 | 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".