Abstract
BACKGROUND: The cardiac consequences of undertaking endurance exercise are the topic of recent debate. The purpose of this review is to provide an update on a growing body of literature, focusing on left ventricular (LV) function following prolonged endurance exercise over 2 h in duration which have employed novel techniques, including myocardial speckle tracking, to provide a more comprehensive global and regional assessment of LV mechanics. METHODS: Prospective studies were filtered independently following a pre-set criteria, resulting in the inclusion of 27 studies in the analyses. A random-effects meta-analysis was used to determine the weighted mean difference and 95% confidence intervals (CI) of LV functional and mechanical data from pre-to-post-exercise. Narrative commentary was also provided where volume of available evidence precluded meta-analysis. RESULTS: A significant overall reduction in LV longitudinal strain (Ɛ) n = 22 (- 18 ± 1 to - 17 ± 1%; effect size (d) - 9: - 1 to - 0.5%), strain rate n = 10 (SR; d - 0.9: - 0.1.3 to - 0.5 l/s) and twist n = 5 (11.9 ± 2.2 to 8.7 ± 2.2°, d - 1: - 1.6 to - 0.3°) was observed following strenuous endurance exercise (range 120-1740 min) (P < 0.01). A smaller number of studies (n = 4) also reported a non-significant reduction in global circumferential and radial Ɛ (P > 0.05). CONCLUSION: The meta-analysis and narrative commentary demonstrated that a reduction in LV function and mechanics is evident following prolonged endurance exercise. The mechanism(s) responsible for these changes are complex and likely multi-factorial in nature and may be linked to right and left ventricular interaction.