Sex Differences in Heart Rate Variability during Metaboreflex Activation
Bibliographic record
Abstract
Women have been shown to experience blunted metaboreflex activation compared to men (Jarvis et al., 2011; Joshi & Edgell, 2019; Minahan et al., 2018; Samora et al., 2020), which may derive from altered autonomic balance. Since heart rate variability (HRV) estimates sympathetic and parasympathetic outflow, this study aims to determine if there are sex differences in HRV during metaboreflex activation. High frequency (HF) power and greater RR interval variability (SDRR) represent cardiac parasympathetic outflow, whereas the ratio between low frequency (LF) and HF power (LF/HF) represents cardiac sympathetic outflow. Thirty-two young, healthy men (n=16) and women (n=16) were recruited to perform 2mins of isometric handgrip at 40% of their maximal voluntary contraction followed by 3mins of post-exercise circulatory occlusion (PECO). ECG was continuously recorded, and HRV analysis was determined using 3mins of ECG at baseline or PECO. In response to PECO, heart rate (Women 71±12bpm vs. 73±13bpm; Men 68±12bpm vs. 72±13bpm; p=0.026) and mean arterial pressure (Women 84±8mmHg vs. 93±10mmHg; Men 85±9mmHg vs. 97±11mmHg; p<0.001) increased equally in both sexes. There were no significant differences in SDRR, root mean square standard deviation, and total power due to sex or PECO (all p>0.07). At all timepoints and compared to men, women had 1) significantly lower LF power (Women 19±10nu vs. 24±16nu; Men 42±21nu vs. 49±17nu; p<0.001), 2) higher HF power (Women 78±9nu vs. 74±16nu; Men 57±20nu vs. 50±17nu; p<0.001), 3) higher proportion of RR intervals differences greater than 50ms (Women 60±21% vs. 58±22%; Men 39±16% vs. 35±20%; p=0.003), regardless of time (p>0.2), and 4) lower LF/HF (Women 0.26±0.17 vs. 0.41±0.42; Men 1.01±0.90 vs. 1.34±1.30; p=0.002). Unlike previous findings, no sex differences were observed in the pressor response to metaboreflex activation. HRV did not differ in response to PECO in both sexes; however, women had greater cardiac parasympathetic dominance than men. Funding provided by Natural Sciences and Engineering Research Council of Canada This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
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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) | 0.003 | 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".