Exercise-induced cardiac remodeling, known as the athlete's heart, corresponds to morphological and functional adaptations of the left ventricle in response to prolonged physical training. It is characterized in particular by physiological hypertrophy and improved myocardial function. Intraventricular blood flow interacts with cardiac mechanics. Regional shape (e.g., sphericity, wall curvature) and myocardial deformations guide flow patterns to create an optimal hemodynamic environment. The interaction between these different parameters in the athlete's heart remains insufficiently explored. In this context, 3D echocardiography makes it possible to combine indices derived from fluid dynamics, regional myocardial function, and cardiac geometry, enabling a comprehensive assessment of cardiac performance. Primary and secondary objectives: In this context, the aim of this project is to investigate the relationship between intraventricular flow and cardiac mechanics based on combined measurements of intraventricular flow (e.g., vorticity, pressure gradients), regional myocardial function (e.g., myocardial strain), and global/regional LV geometry (e.g., sphericity, wall curvature) in the athlete's heart. Since these parameters are interdependent, analyzing their interaction through the development of new echocardiographic tools based on 4D assessments will enable a comprehensive evaluation of functional improvements in the athlete's heart. The secondary objectives are to analyze the impact of dyssynchrony on intraventricular flow, to evaluate the influence of primary and secondary deformations on intraventricular flow, and to study cardiac function from an energetic perspective using non-invasive reconstruction of pressure-volume loops for cardiac work estimation. Methodology: The study will include 80 endurance athletes (ENT group) and 80 control subjects (CONT group). The main inclusion criteria common to both groups are: men and women aged 18-45 years, with no known heart disease and no cardiovascular risk factors (e.g., body mass index \> 30 kg/m², arterial hypertension). Athletes must train at least 10 hours per week for the past 5 years. Control subjects must not engage in more than 3 hours of physical activity per week. Athletes will be recruited from elite groups of various federations, during local long-distance races, or during clinical evaluations at Montpellier University Hospital (Dr. C. Hédon's department). Control subjects will be recruited in the Avignon area and in the cardiology department of Montpellier University Hospital during routine visits. Echocardiographic examinations will be performed in the left lateral decubitus position using Vivid systems with 4D probes. 4D and tri-plane acquisitions with color Doppler will allow assessment of cardiac structure and intraventricular flow. Data analysis will be performed using TOMTEC software, and scripts developed in Matlab and RStudio will process information related to shape, mechanical dispersion, and dyssynchrony. Intraventricular hemodynamics will be analyzed in collaboration with the CREATIS laboratory (D. Garcia), particularly through measurements of intraventricular pressure gradients and vorticity indices.