The Impact of Exercise Induced Dehydration upon Left Ventricular Function after Prolonged Exercise

Abstract

Purpose: The purpose of the study was to determine and examine the effects of a prolonged bout of exercise and exercise induced dehydration upon cardiac function. Methods: The subjects were ten (n=10) competitive cyclists. Each cyclist completed a six hour cycle twice, firstly hydrated and secondly with mild dehydration (loss of one kilo in body weight) at wattage representing 80% of their VO2max. Measurement of cardiac function using echocardiography was taken pre, post and 24 hours post exercise. Measures included: E:A ratio (ventricular compliance), left ventricular tissue velocities (ml), stroke volume (ml), ejection fraction (%), end- diastolic volume (ml), end- systolic volume (ml), left ventricular internal diameter (cm) during diastole and systole. Results: Heart rate (HR) was significantly increased when participants were dehydrated (149±11 compared with 144±7bmp), both systolic and diastolic function were decreased post exercise in both hydrated and dehydrated trials however systolic and diastolic function were further reduced when participants were dehydrated. This can be shown by a further reduction in EDV, SV, E:A ratio and EF post DEH exercise. Left ventricular returned back to baseline levels 24 hours post exercise. Conclusion: We conclude that a prolonged bout of exercise at 80% VO2max induces reductions in systolic and diastolic cardiac function. The impact of exercise induced dehydration further increases these reductions in systolic and diastolic function.