Changes in electrolytes and uric acid excretion during and after a 100 km run.

Physical activity leads to changes in water and electrolyte homeostasis and to enhanced purine metabolism. The typical abnormalities observed after exercise are hyperkaliemia, hyper- or hyponatremia and hyperuricemia. The possible explanations of hyperuricemia are: increased metabolism and decreased elimination of uric acid. Changes in uric acid excretion are commonly observed in disturbances of sodium and water homeostasis. The aim of this study was to evaluate changes in electrolytes and uric acid excretion during a very long period of exercise. Twenty subjects with a mean age of 40.75±7.15 years took part in a 100 km run. The route of the run was based on the university stadium track. All subjects were experienced amateur runners, with a mean time of regular running of 6.11±7.19 years. Blood was collected before the start, after every 25 km and 12 hours after the run. The levels of electrolytes, creatinine, uric acid, cortisol, aldosterone, creatine kinase, C-reactive protein and interleukin-6 were measured. Creatinine clearance, urinary potassium-to-sodium ratio, fractional excretion of electrolytes and uric acid were calculated. Seventeen runners completed the study. Significant increases in sodium (from 141.65±1.90 to 144.29±3.65mmol/l), potassium (from 4.53±0.34 to 5.03±0.42mmol/l), creatinine (from 0.88±0.11 to 1.10±0.20mg/dl) and uric acid (from 5.15±0.87 to 5.94±1.50 mg/dl) were observed after 100 km (p less than 0.05). Other significant changes during the study were noted in fractional excretions of sodium (from 0.86±0.29 to 0.33±0.13%) and potassium (from 6.66±2.79 to 18.90±10.01%), probably reflecting the decrease in renal blood flow (RBF) and increase in renal tubule reabsorption. The fractional excretion of uric acid slightly increased but without statistical significance from 5.34±1.51 to 6.09±2.34%. The results of our study showed that during very long but not very intensive exercise there is no change in uric acid excretion, although at the same time profound changes in electrolyte excretion are found. Both hyperuricemia and hyperuricosuria may be harmful, therefore it seems logical that the best way to avoid those abnormalities is to maintain fractional uric acid excretion.

Running a 100-km ultra-marathon induces an inflammatory response but does not raise the level of the plasma iron-regulatory protein hepcidin.

AIM: Exercise may induce an inflammatory response that may lead to changes in iron metabolism. The aim of this study was to examine the relationship between the inflammation induced by a 100 km run and the level of hepcidin, which is a hormone regulating iron metabolism. METHODS: Six males, age 44.5±13.5 years, running 100 km. SETTING: the CRP protein, IL-6 and leucocyte count were measured as an index of inflammation. RESULTS: A 100 km run caused a progressive increase in blood IL-6 concentration, which reached the highest values after 75 km. Furthermore, an increase in levels of CRP, a marker of inflammation, was observed after the 100 km run and continued to increase after a 14 h recovery period. Leucocyte number and markers of muscle damage were significantly elevated after the 100 km run. This was accompanied by a decrease in transferrin saturation and an increase in blood haemoglobin and ferritin. Despite all these changes, the 100 km race did not affect blood hepcidin concentration either during the run or after a 14 h recovery period. CONCLUSION: The study shows that a 100 km run induces an inflammatory response but does not trigger changes in the blood hepcidin level. Thus it can be concluded that changes in IL-6 are not sufficient to increase the blood hepcidin level in runners.