Short‐term changes in the blood leucocyte and platelet count following different durations of high‐intensity treadmill running

Publisher Website
Google Scholar
Abstract
Short‐term changes in the blood leucocyte count after exercise are known to be dependent on the intensity of exercise performed. The aim of the present study was to investigate the effects of the duration of high‐intensity exercise on changes in the leucocyte and platelet count during the early recovery period. On separate occasions following a standard warm‐up, eight healthy subjects (six males, two females) ran at a constant speed of 5.6 m s‐1 (20 km h‐1) on a level treadmill for 30, 60, 90, 120 or 150 s or to fatigue. Heart rates were increased to near maximal levels within 30 s of exercise. Significant increases in the blood leucocyte count occurred after all exercise durations compared with baseline (pre‐exercise) levels. Running for 30 s increased the blood leucocyte count by 35 ± 10% (x±S.D.). Running for 60 s increased the blood leucocyte count by 57±16%, but running for longer durations did not produce any further significant increase in the immediately post‐exercise blood leucocyte count. After exercise to exhaustion, the leucocyte count had increased by 63±17%. This was mainly due to an increase of lymphocytes (114±20%) rather than neutrophils (34±7%). At exhaustion, plasma volume had decreased by 15.9±2.6% compared with pre‐exercise. During 5 min of recovery from exercise, the leucocyte count fell significantly (after 30 and 60 s of running), remained unchanged (90 and 120 s) or increased significantly (150 s and fatigue) compared with immediately post‐exercise. The further increases in the leucocyte count observed during the recovery period after running for 150 s or to fatigue were almost exclusively due to increases in the number of circulating neutrophils, and were not due to haemoconcentration. There was a significant correlation between the magnitude of the change in the leucocyte count during recovery from exercise and the plasma lactate concentration (r=0.83, P<0.01). We conclude that for high‐intensity running exercise, the duration of running at a constant speed has a marked effect on the magnitude of the exercise leucocytosis and on the direction of change in the blood leucocyte count during the early recovery period. Further rises in circulating leucocytes and platelets in the recovery period may be caused by the effects of lactacidosis.