Early changes of the anemia phenomenon in male 100-km ultramarathoners

Sports anemia is a widely observed phenomenon after prolonged running. There are various factors that contribute to sports anemia, including hemodilution, exercise-induced oxidative stress, iron deficiency, gastrointestinal bleeding, hematuria, and hemolysis resulting from foot-strike and/or from compression of contracting muscles on capillaries. Until now, there has been no published report that describes the overall hematological, urinary, and fecal consequences in Asian male ultramarathoners after a 100-km (62.5-mile) ultramarathon event.

A total of 25 male runners were recruited into our study. Blood was drawn 1 week before, immediately after, and then 24 hours subsequent to the race. Hematological samples were analyzed for the anemia phenomenon. Additionally, urinary and fecal samples were collected before and after the race for detection of occult blood.

The blood hemoglobin and erythropoietin values of the recruited runners showed a statistically significant rise in the immediate post-race values and a rapid drop in values at 24 hours post-race. Blood concentrations of red blood cells and hematocrit were significantly lower at 24 hours post-race compared with pre-race. The white blood cell count, interleukin-6, tumor necrosis factor-alpha, high-sensitivity C-reactive protein, and ferritin all showed significant increases both immediately after and 24 hours post-race compared with pre-race hematological values. There were immediate decreases of both haptoglobin and iron, as well as an increase of total iron-binding capacity levels in post-race blood tests. For both urinary and fecal samples, there was a statistically significant difference between the pre- and post-race results in occult blood.

Running a 100-km ultramarathon will induce substantial sports anemia, and oxidative stress response, hemolysis, hematuria, and gastrointestinal bleeding are typical factors that contribute to its onset.