Intravascular haemolysis in the recreational runner

Intravascular haemolysis has been found to result from prolonged endurance competition, rigorous military training and participation in impact sports. Haematological research involving the recreational runner is sparse. Recreational runners frequently vary their training to avoid monotony and improve endurance capacity. This study investigated the haematological effects of a typical day of increased distance training in 15 male recreational runners (62.4(3.1) ml kg-1 min-1 treadmill VO2max; 44.6(8.4) km per week training (means(s.d.)). Venous blood samples were collected before, immediately after, 1 day, 4 days, and 10 days after a 13-km training run (about twice the subjects' typical running distance) and analysed for changes in bilirubin, serum potassium, haematocrit, haemoglobin, red blood cell count, haptoglobin, poikilocytosis and reticulocytosis. Urine samples were collected at the same times as the blood samples and analysed for urobilinogen. Significant (P less than 0.05) 1-day and 4-day decreases in mean haemoglobin, red blood cell count, and haptoglobin values, compared to before training venous blood values and significant (P less than 0.05) post-training increases in bilirubin, serum potassium, urobilinogen and poikilocytosis provided evidence for increased intravascular haemolysis. After 10 days the values for haematocrit, bilirubin, serum potassium, red blood cell count, urobilinogen and poikilocytosis were not significantly (P less than 0.05) different from pre-training values while haemoglobin remained significantly (P less than 0.05) lower, exhibiting a constant but not significant increase over the period from 1 to 10 days. The results indicate that mild intravascular 'footstrike' haemolysis can occur in the recreational runner when typical training distance is increased. This condition appears to be transient and benign.