Effect of aging on the hemodynamic and sympathetic response at the onset of isometric handgrip exercise
Bibliographic record
Abstract
This study determined whether sympathetic inhibition occurs at the onset of isometric handgrip exercise (HG). We also determined whether age affects the hemodynamic and sympathetic responses to HG. Twelve young and 16 older individuals (age: 24 ± 3 vs.60 ± 9 years) performed four 20‐second HG at 30, 40 and 50% of maximum voluntary contraction (MVC). Beat‐by‐beat heart rate (HR), mean arterial pressure (MAP), cardiac output (Q) and total peripheral resistance (TPR) were assessed by Modelflow, and burst frequency and burst incidence of muscle sympathetic nerve activity (MSNA) were obtained by microneurography. Baseline MSNA burst frequency and incidence were higher in older vs. young individuals (24±9 vs. 12±5 bursts/min, 41±14 vs. 18±8 bursts/100 heartbeat, p<0.001). At 30% MVC, there was no HG effect on HR, MAP, Q, TPR, bursts frequency and incidence in comparison to baseline. At 40% MVC, HG increased HR alone (main effect, p=0.01). At 50% MVC, HG increased HR and burst frequency (main effect, p<0.01). An age effect was observed at 50% MVC, where HG increased HR to a greater extent in young vs. older individuals (15±10 vs. 8±5 bpm, p=0.02). There was no evidence of sympathetic inhibition at the onset of HG in either young or older individuals. Age reduced the HR response but had no impact on the sympathetic response at the onset of HG. This study was funded by CIHR.
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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 | 0.001 |
| 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".