Influence of Endurance Training, High-Intensity Interval Training, and Acute Exercise on Left Ventricular Mechanics:...

Background: Left ventricular (LV) mechanics assessed by speckle-tracking echocardiography provides sensitive markers of cardiac adaptation to exercise. Different training modalities-endurance, high-intensity interval training (HIIT), and acute exercise tests-impose distinct hemodynamic loads, yet their comparative effects on LV deformation remain unclear. Importantly, acute and chronic endurance exposures may elicit divergent myocardial responses that must be interpreted separately. Methods: A systematic search of PubMed, Scopus, and EMBASE (through September 2025) identified studies evaluating LV mechanics in response to endurance, HIIT, or acute exercise among healthy or recreationally active individuals. Echocardiographic parameters of strain and torsion were extracted, and methodological quality was appraised using the NIH Quality Assessment Tool. Results: Twenty-three studies (859 participants) met inclusion criteria. Acute prolonged endurance exercise-particularly marathon and ultra-endurance events-was associated with transient, fully reversible reductions in global longitudinal, circumferential, and radial strain and torsion, despite preserved ejection fraction, reflecting short-term myocardial fatigue rather than maladaptive remodeling. In contrast, chronic endurance training maintained or improved LV mechanics without evidence of dysfunction, while HIIT interventions consistently enhanced LV systolic strain and rotational indices across diverse age groups and sexes, reflecting improved contractile efficiency and physiological remodeling. Acute exercise produced heterogeneous, load-dependent strain responses, with isometric stress increasing regional strain and maximal exertion inducing temporary global reductions. Between-study heterogeneity was moderate, methodological quality generally good, and small-study effects varied by modality, being most evident in endurance studies, borderline for HIIT, and limited for acute tests due to sample size. Conclusions: Acute endurance exercise produces transient, reversible LV deformation changes, whereas chronic endurance training preserves mechanical efficiency. HIIT reliably enhances systolic strain and torsional mechanics, and acute exercise elicits variable but physiologically meaningful responses. These findings clarify that transient post-race strain reductions reflect physiological fatigue, not chronic maladaptation, and underscore the modality-specific nature of myocardial adaptation to exercise.