Sex-specific impact of aging on muscle sympathetic neural discharge patterns during incremental rhythmic handgrip exercise
Bibliographic record
Abstract
Sex-disparities exist in the risk of developing hypertension throughout the lifespan, with a greater prevalence of hypertension amongst postmenopausal females compared to similarly aged males. Though the underlying mechanisms are multifactorial, exaggerated sympathetic neuro-cardiovascular reactivity may be an important contributor. Indeed, postmenopausal females exhibit exaggerated exercise pressor responses compared to young adults, and older males. However, the interactive effects of age and sex on muscle sympathetic nerve activity (MSNA) and action potential (AP) coding patterns during exercise remains unclear. We hypothesized that older females would exhibit the greatest increase in MSNA and AP recruitment during exercise and post-exercise circulatory occlusion (PECO) relative to young males and females, as well as older males. MSNA and AP discharge patterns (microneurography and continuous wavelet transform) were assessed in 12 young males (YM (mean±SD); 26±4, years), 11 young females (YF; 25±4 years), 11 older males (OM; 71±11 years), and 12 older females (OF; 71±4 years) during incremental rhythmic handgrip exercise to fatigue followed by 2 minutes of PECO. At peak exercise, OM demonstrated a smaller change from baseline (Δ) in MSNA burst incidence (BI) compared to all other groups (YM: Δ8±9, YF: Δ9±8, OM: Δ-6±8, OF: Δ6±7 bursts/100heartbeats; all ANOVA post-hoc P<0.05), whereas ΔMSNA burst frequency (BF), Δburst amplitude (BA), and Δtotal activity were not different between groups (all P>0.05). Conversely, YM demonstrated greater ΔAPs/burst (YM: Δ5±3, OM: Δ0.4±3, OF: Δ2±2 APs/burst; post-hoc P<0.05) and ΔAP clusters/burst (YM: Δ2±1, OM: Δ0.1±1, OF: Δ0.7±0.7 Clusters/burst; post-hoc P<0.05) compared to OM and OF, but not compared to YF (Δ2±3 APs/burst and Δ0.9±0.8 clusters/burst; both P≥0.07). However, no group differences were observed in the recruitment of larger axons (YM: Δ6±2, YF: Δ4±2, OM: Δ2±5, OF: Δ4±3 clusters; P=0.33). Contrary to exercise, group-by-time interactions existed during PECO for ΔMSNA BF ( P<0.01), ΔBI ( P<0.01), and Δtotal activity ( P<0.01) where greater increases occurred during the first minute of PECO in young compared to older adults (all post-hoc P<0.05), whereas in the final minute of PECO, MSNA ΔBF and ΔBI were only greater in YM compared to OM and OF (all P<0.05), and total activity was greater in YM and YF compared to OF only (all P<0.05). No group-by-time interactions were observed for ΔMSNA BA ( P=0.37), ΔAPs/burst ( P=0.94), ΔAP clusters/burst ( P=0.95) or Δtotal AP clusters ( P=0.41) during PECO. Altogether, MSNA and AP reactivity during exercise was not exaggerated in OF, but age-related reductions in AP recruitment were observed in males. During PECO, MSNA responses were lower in older relative to young adults but, AP recruitment was unaltered by age. Thus, exaggerated MSNA or AP reactivity may not explain the greater prevalence of hypertension in OF. Supported by the Natural Sciences and Engineering Council of Canada, and IEEM Indirect Funds. 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 | 0.000 |
| 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".