Sex differences in cardiac adaptation and training patterns in elite cyclists

Abstract Background Endurance athletes commonly exhibit exercise-induced cardiac remodelling, characterised by a symmetrical increase in cardiac dimensions. These adaptations, often referred to as ‘athlete’s heart’, can be particularly pronounced in elite endurance athletes such as competitive cyclists. Existing work relating cardiac remodelling to training load has mostly relied on self-reported training data, and female athletes remain underrepresented in literature. We therefore aimed to evaluate sex differences in cardiac volumes and mass in elite competitive cyclists and to quantify the relationship between objectively measured training load and cardiac structure in both sexes. Methods We studied a cohort of young elite cyclists (median age 21 19 – 25 years) recruited from the multicentre Pro@Heart study. Cardiac MRI was used to quantify biventricular volumes, mass, and function. Cardiopulmonary exercise testing determined VO2peak. Chest-worn heart rate (HR) data were collected over 12 months to quantify total number of activities, exercise duration and time spent in each HR zone. Individualised HR zones were derived using the tangent method based on the maximal recorded HR. Edwards TRIMP (eTRIMP) was calculated to integrate training volume and intensity. Results Male athletes (n = 87) had larger absolute and BSA-indexed left and right ventricular volumes compared to female athletes (n = 45). VO2peak was greater in males (67 67 – 74 vs 55 49 – 59 mL/kg/min, p0.001). Total 12-month training duration was higher in male athletes, whereas eTRIMP did not differ significantly between sexes. Male cyclists spent more time in HR zones 1 and 2, while female cyclists spent more time in zones 4 and 5 (Table 1). In male cyclists, total training duration and time in HR zone 1 correlated positively with LV volumes and mass. In female cyclists, total training duration correlated with LV mass but not volumes. Time in low-intensity HR zones did not correlate with LV volumes in females. Conversely, time in high-intensity HR zones (4 – 5) was inversely correlated with LV volumes (Figure 1). Conclusion In elite competitive cyclists, exercise patterns differ substantially: Male athletes exhibit greater total exercise volume, cycling longer in lower-intensity HR zones, whereas female athletes performed proportionally more at high intensity. Total exercise duration correlated positively with LV volumes and mass in males, but only with LV mass in females. Time spent in low-intensity HR zones correlated with LV volumes in male athletes but not in female athletes. These findings suggest sex-specific relationships between exercise patterns and cardiac remodelling, potentially including autonomic adaptations, in elite endurance athletes.For image description, please refer to the figure legend and surrounding text. For image description, please refer to the figure legend and surrounding text.