Maintained serum sodium in male ultra-marathoners : the role of fluid intake, vasopressin, and aldosterone in fluid and electrolyte regulation

Exercise-associated hyponatremia (EAH) is a well know electrolyte disorder in endurance athletes. Although fluid overload is the most like etiology, recent studies, however, argued whether EAH is a disorder of vasopressin secretion. The aims of the present study were to investigate (i) the prevalence of EAH in male ultra-marathoners and (ii) whether fluid intake, aldosterone or vasopressin, as measured by copeptin, were associated with post-race serum sodium concentration ([Na+]). In 50 male ultra-marathoners in a 100 km ultra-marathon, serum [Na+], aldosterone, copeptin, serum and urine osmolality, and body mass were measured pre- and post-race. Fluid intake, renal function parameters and urine excretion were measured. No athlete developed EAH. Copeptin and aldosterone increased; a significant correlation was found between the change in copeptin and the change in serum [Na+], no correlation was found between aldosterone and serum [Na+]. Serum [Na+] increased by 1.6%; body mass decreased by 1.9 kg. The change in serum [Na+] and body mass correlated significantly and negatively. The fluid intake of ~ 0.58 l/h was positively related to the change in body mass and negatively to both post-race serum [Na+] and the change in serum [Na+]. We conclude that serum [Na+] was maintained by both the mechanisms of fluid intake and the hormonal regulation of vasopressin

Fluid intake and changes in limb volumes in male ultra-marathoners: does fluid overload lead to peripheral oedema?

An increase in body mass due to oedema has been previously described. The aim of this study was to investigate a potential association between both fluid and electrolyte intake and the formation of peripheral oedemas. Fluid and electrolyte intakes and the changes in limb volumes in 50 male 100-km ultra-marathoners were measured. Pre- and post-race serum sodium concentration ([Na(+)]), serum aldosterone concentration, serum copeptin concentration, serum and urine osmolality and body mass were determined. Fluid intake, renal function parameters and urinary output, as well as the changes of volume in the extremities, were measured. The changes of volume in the limbs were measured using plethysmography. Serum [Na(+)] increased by 1.6%; body mass decreased by 1.9 kg. Serum copeptin and aldosterone concentrations were increased. The change in serum copeptin concentration and the change in serum [Na(+)] correlated positively; the change in serum [Na(+)] and body mass correlated negatively. A mean fluid intake of 0.58 L/h was positively related to running speed and negatively to post-race serum [Na(+)]. Total fluid intake was positively related to the changes in both arm and lower leg volumes. Running speed was positively associated with the changes in arm and lower leg volumes; race time was related to the changes in serum copeptin or aldosterone concentrations. To conclude, fluid intake was related to the changes in limb volumes, where athletes with an increased fluid intake developed an increase in limb volumes

Is the prevalence of exercise-associated hyponatremia higher in female than in male 100-KM ultra-marathoners?

Purpose. The prevalence of exercise-associated hyponatremia (EAH) has mainly been investigated in male endurance athletes. The aim of the present study was to investigate the prevalence of EAH in female 100-km ultra-marathoners and to compare them to male ultra-runners since females are considered more at risk of EAH. Methods. Changes in body mass, hematocrit, [Na+] and [K+] levels in both plasma and urine, plasma volume, urine specific gravity, and the intake of energy, fluids and electrolytes was determined in 24 male and 19 female 100-km ultra-marathoners. Results. Three male (11%) and one female (5%) ultra-marathoners developed asymptomatic EAH. Body mass decreased, while plasma [Na+], plasma [K+] and hematocrit remained stable in either gender. Plasma volume, urine specific gravity and the potassium-to-sodium ratio in urine increased in either gender. In males, fluid intake was related to running speed (r = 0.50, p = 0.0081), but not to the change in body mass, in post-race plasma [Na+], in the change in hematocrit and in the change in plasma volume. Also in males, the change in hematocrit was related to both the change in plasma [Na+] (r = 0.45, p = 0.0187) and the change in the potassium-to-sodium ratio in urine (r = 0.39, p = 0.044). Sodium intake was neither related to post-race plasma [Na+] nor to the change in plasma volume. Conclusions. The prevalence of EAH was not higher in female compared to male 100-km ultra-marathoners. Plasma volume and plasma [Na+] were maintained and not related to fluid intake, most probably due to an activation of the reninangiotensin-aldosterone-system