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Background: The consequences and risks of prolonged physical exercise are not well established.

Objective: To evaluate the effects of prolonged physical exercise on the participants of a 24-hour ultramarathon race.

Methods: Twenty male runners were selected for evaluation a day before and immediately after the race, where the athletes had to cover the most distance in 24 hours. Clinical, laboratory and echocardiographic data were obtained at both evaluations.

Results: Mean distance covered was 140.3±18.7 km. Runners showed weight loss (p< 0.001) and decrease in systolic (p< 0.001) and diastolic (p= 0.004) blood pressure. Hematological changes were compatible with the physiological stress. Plasma levels of creatine phosphokinase strikingly increased post-race (163.4±56.8 vs. 2978.4±1921.9 U/L; p< 0.001) and was inversely correlated with distance covered: those who covered the longest distances showed the lowest CPK levels (Pearson r= 0.69, p= 0.02). After the race, 2 runners showed a slight increase in Troponin levels. One of them also had simultaneous decrease in left ventricular ejection fraction (coronary artery disease was subsequently ruled out). Basal echocardiography assessment had shown LV hypertrophy in one and increased left atrial volume in five runners. After the race, there was a decrease in E/A ratio (p< 0.01).

Conclusion: Prolonged physical exercise is associated with metabolic and cardiovascular alterations. Cardiac abnormalities found in our study suggest that cardiac fatigue may occur in this specific race modality. The long-term effect of these alterations, while maintaining the routine practice of prolonged …