Brachial Artery Flow-Mediated Dilation Variability During Incremental Or Single Intensity Bouts Of Handgrip Exercise
Bibliographic record
Abstract
The stimulus response relationship between shear stress (SS) and endothelial dependent flow-mediated dilation (FMD) has not been thoroughly characterized. Also, it is currently unknown whether FMD in response to a specific SS will differ when that stimulus is reached in a single step vs. incremental steps of exercise. PURPOSE: 1) To assess the linearity and day-to-day slope variability of the SS-FMD stimulus response relationship within the brachial artery (BA) and 2) To compare the %FMD when a specific shear target is reached in a single step vs. when that same shear is attained via multiple shear increments. METHODS: N=6 healthy subjects (1 male). BA diameter (BAD) and blood velocity (BV) were assessed with echo and Doppler ultrasound. SS was estimated as shear rate (SR=BV/BAD) and is reported as the mean SR in last minute of exercise. Subjects performed 4 handgrip exercise trials: 2 single steps (SR target 70s-1) and 2 incremental steps (SR targets 25s-1, 40s-1, 55s-1, 70s-1, 85s-1) on each of two visits. Like trials performed on the same day were averaged. Linear regression analysis was performed on individual subject data to characterize the within subjects SR-FMD relationship. RESULTS: Data are means ± SD. CV=co-efficient of variation. Incremental steps: There was a strong positive relationship between SR and %FMD (r2=0.87 ± 0.11) (individual r2 range = 0.68 - 0.98). The SR-%FMD slope was not significantly different on day 1 (0.22 ± 0.13) vs. day 2 (0.12 ± 0.04, p=0.158); however, there was considerable day-to-day slope variability (CV = 40.40 ± 0.08%). Single step: There was no significant difference in the %FMD on day 1 6.61 ± 1.50% vs. day 2 5.39 ± 1.90% (p = 0.206). The within subject absolute difference (ABSdiff) in %FMD between day 1 and day 2 was 1.61 ± 1.73%. Single vs. Incremental step: The %FMD at SR 70s-1 did not differ when reached via a single step (6.00 ± 2.21%) vs. incremental steps (6.44 ± 2.05%) (p = 0.876). The ABSdiff in %FMD between day 1 and day 2 in the incremental trials at shear 70s-1 was 2.37 ± 2.59% (p = 0.589 vs. single step ABSdiff). CONCLUSIONS: The endothelium responds similarly to matched SR targets that are achieved either in a single step or in a series of incremental increases. There is a strong SR-FMD relationship, however it appears there may be substantial day-to-day slope variability. Supported by NSERC and CFI
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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 | 0.002 |
| 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".