Objective:

To quantify fitness-specific three-dimensional echocardiographic reference values categorized by V̇O2peak and characterize the ‘recreational athlete’s heart’ and its sex-specific adaptations, specifically defining 'recreational athlete' as individuals engaging in regular physical activity.

Key Findings:

• Both sexes showed increases in 3DE end-diastolic volume with fitness, with specific volume metrics provided.
• Men exhibited greater cardiac remodelling than women at a given V̇O2peak, with detailed metrics.
• Ratios of heart chamber volumes remained constant across fitness levels, with specific ratios included.
• LV mass/volume ratio decreased slightly with increasing fitness without relevant sex differences, with specific metrics provided.

Interpretation:

The study establishes sex- and fitness-specific 3DE reference values, indicating that recreational athletes' hearts adapt physiologically to increased fitness levels, with notable differences between sexes.

Limitations:

• Study focused on a specific age range (18-35 years) and may not generalize to older populations, which could limit applicability in clinical settings.
• Cross-sectional design limits causal inferences about fitness and cardiac adaptations, suggesting the need for longitudinal studies.

Conclusion:

This study provides essential reference values for 3DE measurements in recreational athletes, aiding in the differentiation between physiological and pathological cardiac changes, which is crucial for clinical assessments.