Haematological changes associated with endurance exercise.

Blood counts and noradrenaline estimations were performed in 14 horses competing in a 160 km endurance ride. Samples were collected before the ride, immediately after the ride. 30 minutes after the ride and the day after the ride. For statistical analysis, a group of seven horses that completed the ride at a mean speed of 234 m/minute (fast group) was compared with seven horses that completed the ride at a mean speed of 144 m/minute (slow group). Immediately after the ride the fast group of horses had higher packed cell volume, haemoglobin, neutrophils and lower lymphocyte counts than the slow group of horses. Thirty minutes after the ride the fast group had higher neutrophil and lower lymphocyte counts than the slow group. In the fast group of horses significant increases in packed cell volume, haemoglobin and red cell count occurred immediately after the ride, but these parameters remained unchanged in the slow group of horses. Significant correlations were found for heart rate, speed and noradrenaline concentrations with packed cell volume, haemoglobin, red cell counts percentage of neutrophils and percentage of lymphocytes, for values immediately after the ride.