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

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.(ABSTRACT TRUNCATED AT 250 WORDS)