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This article discusses the concept of a reserve in myocardial work capacity during exercise in healthy individuals. The study aimed to determine if there is a reserve in myocardial work that is not mobilized during incremental exercise. The researchers recruited 11 healthy young individuals and conducted testing sessions to measure myocardial work and its underlying functional components. The results showed that there is no reserve in myocardial work capacity during exercise, suggesting that incremental exercise may elicit truly maximal myocardial work capacity under healthy physiological conditions. Further research is needed to understand the mechanisms that regulate myocardial work and its adaptations to endurance training. [Extracted from the article]

Physiology underlying reduced cardiac pumping capacity in women compared with men and its interaction with aging remains unresolved. Herein, the pressure gradient (PG) driving venous return was manipulated to evidence whether cardiac structure and/or function explain sex differences in cardiac capacity. Healthy women/men matched by age and physical activity were included within young (n  = 40, age = 25 ± 4 years) and older (n  = 55, age = 60 ± 8 years) groups. Cardiac volumes/output (Q) were assessed up-to-peak exercise under 2 hemodynamic conditions ("low"/"high" PG between lower/upper body). Main outcomes included sex differences in delta ("high" − "low" PG) left ventricular (LV) end-diastolic volume (∆LVEDV), stroke volume (∆SV), and Q (∆Q). In young individuals, "high"-PG increased exercise LVEDV and SV in men (p  ≤ .002), but not in women (p  ≥ .562), relative to "low"-PG (control condition). Accordingly, peak ∆LVEDV, ∆SV, and ∆Q were enhanced in young men versus young women (p  ≤ .019). Notwithstanding, right/left atrial volumes during exercise were similarly increased by "high"-PG in both young sexes (p  ≤ .007). "High"-PG exclusively prolonged moderate exercise LV filling time in young men (p  ≤ .036). In older individuals, "high"-PG did not modify exercise cardiac volumes and reduced LV diastolic function (p  ≤ .049). In conclusion, the female young heart is unrestrained by venous return or structural factors external to the myocardium. As determined during moderate exercise, impaired LV filling time lengthening limits female-specific cardiac capacity. With older age, cardiac chambers are not distended and LV relaxation is impaired with increased PG in both sexes. During early but not late adulthood, a functional LV limitation may explain sex differences in cardiac capacity. [ABSTRACT FROM AUTHOR]

Background: The physiology of prominent prognostic factors in the cardiorespiratory system remains unchartered in the world's largest ethnic group: Hans Chinese (HC). This study assessed and contrasted the fundamental variables in HC and European-American (EA) individuals., Methods: Healthy HC and EA adults ( n  = 140, 43% ♀) closely matched by age, sex and physical activity were included. Body composition (DXA) and haematological variables (haemoglobin mass, blood volume (BV)) were measured at rest. Pulmonary O 2 uptake (VO 2 ) measurements along with cycle ergometry designed for accurate transthoracic echocardiography were implemented to assess cardiorespiratory structure/function up to peak effort., Findings: HC presented with higher body fat and lower lean body mass (LBM) percentage than EA irrespective of sex ( P  ≤ 0.014). BV did not differ whereas blood haemoglobin concentration was lower in HC compared with EA, particularly in females ( P  = 0.009). Myocardial diastolic and overall function at rest was enhanced in HC versus EA ( P  < 0.001). During exercise, heart volumes and output per unit of body size did not differ between ethnicities, whereas larger heart volumes per unit of LBM were found in HC versus EA in females ( P  ≤ 0.003). At high exercise intensities, VO 2 (-16%) and the arteriovenous O 2 difference (-28%) were markedly reduced in HC compared with EA in females ( P  ≤ 0.024). In males, no physiological difference between HC and EA was observed during exercise., Interpretation: Notwithstanding lower LBM, HC are characterised by similar BV and cardiac capacity but reduced peak VO 2 than EA in females, partly explained by low ethnic-specific blood O 2 carrying capacity., Funding: Early Career Scheme (106210224, to D.M.) and Seed Fund (104006024, to D.M.)., Competing Interests: We declare no conflict of interest., (© 2023 The Author(s).)