Does prolonged endurance exercise reduce left ventricular function in exercising individuals?
Prolonged endurance exercise is associated with a short-term reduction in systolic and diastolic left ventricular function, which is partially explained by altered cardiac loading.
PURPOSE: Evidence supporting cardiac fatigue following prolonged endurance exercise remains equivocal. The purpose of this meta-analysis was to quantify all data fulfilling the specified inclusion criteria, examining the short-term effect of prolonged endurance exercise on left ventricular function. METHODS: A random effects meta-analysis of the weighted mean change in ejection fraction (EF), systolic blood pressure/end systolic volume (SBP/ESV) ratio, and early-to-late diastolic filling (E/A) was conducted on 23 studies using the SE of the between-subjects SD. HR, SBP, and left ventricular internal diameter during diastole (LVIDd) were also analyzed. Studies were coded according to exercise duration and training status: moderate duration trained (MDt) and untrained (MDu), 60-150 min; long duration (LD), 166-430 min; and ultra duration (UD), 640-1440 min. Relationships were assessed via Pearson's product-moment correlation. RESULTS: A significant (P < 0.05) overall decrease in EF (mean, confidence interval (CI): -1.95%, -1.03 to -2.88%), SBP/ESV (mean, CI: -0.8, -0.63 to -0.97), and E/A (mean, CI: -0.45, -0.39 to -0.51) was observed. Only UD and MDu subgroups demonstrated a reduction in EF. All subgroups demonstrated significant (P < 0.05) decreases in E/A. Alterations in LVIDd and SBP were related to respective decreases in EF and SBP/ESV, but not to E/A. CONCLUSION: The decrease in EF and SBP/ESV observed in UD and MDu indicates a reduction in systolic function, partially explained by altered cardiac loading. A decrease in E/A in all subgroups, unrelated to changes in loading, suggests an intrinsic impairment of left ventricular relaxation. Future investigators should employ load-independent indices of cardiac function and attempt to uncover the mechanisms of this phenomenon.
Middleton et al. (2006) studied this question.