Sex Differences in Left Ventricular Stroke Volume During Muscle Metaboreflex Activation
Notice bibliographique
Résumé
Introduction: Muscle metaboreflex activation (MMA) increases blood pressure, possibly by disproportionate increases in left ventricular (LV) stroke volume (SV) in males compared to females due to greater grip strength and metabolite production. The purpose of this study was to determine the effect of sex on SV during isolated MMA using cardiac MRI in young healthy adults. We hypothesized that SV would increase during MMA to a greater degree in males compared to females, and that this effect would be negated by accounting for grip strength. Methods: Ten males [23(2) yrs] and 10 females [26(5) yrs] underwent cardiac MRI during rest, 30% maximal voluntary contraction (MVC) isometric handgrip exercise (6 min), and isolation of MMA with brachial cuff circulatory occlusion (6 min). SV, end-systolic (ESV) and end-diastolic volumes (EDV) were measured by 2- and 4-chamber cine images and indexed (i) to body surface area to account for body size. Heart rate (HR, ECG) and mean arterial pressure (MAP, brachial cuff) were recorded. Cardiac output index (COi) and total peripheral resistance (TPR) were calculated. Analyses included ANOVA (sex × condition), ANCOVA [100% MVC (M=49(13) kg, F=26(7) kg) covariate], and linear regression. Results: SVi decreased from rest to MMA in males [67(8) to 61(5) mL/m 2 , p=0.0001] but not females [59(9) to 59(7) mL/m 2 , p=0.998; interaction p=0.002]. Notably, the reduction in SVi during MMA in males ( p=0.002) but not females ( p=0.957) remained with ANCOVA using MVC as the covariate (interaction p=0.021). ESVi increased during MMA in males [39(5) to 48(10) mL/m 2 , p<0.0001] but not females [32(5) to 36(6) mL/m 2 , p=0.092; interaction p=0.029]. MMA decreased both EDVi ( p=0.004) and COi ( p=0.045) and increased both MAP ( p<0.0001) and TPR ( p<0.0001) pooled across sex. HR did not change with MMA in either sex (all p≥0.093). Linear regression revealed significant relationships between ΔSVi and ΔESVi in males ( p=0.002, R 2 =0.709) but not females ( p=0.223, R 2 =0.179) and between ΔSVi and ΔTPR in males ( p=0.005, R 2 =0.649) but not females ( p=0.522, R 2 =0.053). Conclusions: MMA lowers SVi in males but not females, even when accounting for grip strength and despite similar pressor responses in both groups. These findings from gold-standard MRI suggest differential LV responses to MMA between sexes, potentially related to greater sensitivity to increased TPR in males than females. Thus, sex differences in blood pressure control during MMA may be impacted by differences in LV afterload sensitivity. Further, the blood pressure response to MMA may be primarily mediated through TPR and not CO in healthy young adults. Heart and Stroke Foundation of Canada. This is the full abstract presented at the American Physiology Summit 2024 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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Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».