Exercise-Induced Fluid Retention, Cardiac Volume Overload, and Peripheral Edema in Ultra-Distance Cyclists

Abstract

IntroductionUltracyclists expose themselves to extreme physical challenges. This study aimed to elucidate the effects of ultracycling on electrolyte and fluid balance and investigate the potential occurrence of peripheral edema. MethodsSerial laboratory analyses of blood and urine, bioelectrical impedance analyses and echocardiography were performed at four time points during a six-day bicycle ride in 13 ultracyclists (5 female, 8 male). Throughout the ride, participants continuously tracked fluid intake, measured extremity circumferences daily, and self-tested urinary electrolytes using a point-of-care testing device. Portrait photos were judged by 20 physicians for occurrence of facial and eyelid edema. ResultsParticipants covered a mean distance of 1,205 km and 19,417 vertical meters. From baseline to day 6, body weight remained stable (p = 0.479), but body composition changed with increasing total body water (+1.98 L ± 1.37, p = 0.003) and plasma volume (+18.86 % ± 10.7, p < 0.001). A significant increase in NT-proBNP (+297.99 ng/L ± 190.42, p < 0.001) until day 6 indicates concomitant cardiac volume overload. Swelling of face and eyelids peaked on day 5 (both p ≤ 0.033). On recovery, changes partly resolved. While urinary sodium concentration showed a nadir on day 4 (-32.18 mmol/L ± 23.88, p = 0.022), plasma osmolality (+5.69 mmosmol/kg ± 5.88, p = 0.004) and copeptin (+38.28 pg/mL ± 18.90, p < 0.001) increased steadily until day 6. ConclusionUltracycling over multiple days induces extracellular volume expansion, peripheral edema and cardiac volume overload. Renal sodium and water retention is likely contributing to this condition.