DIFFERENTIAL WHITE CELL COUNT AFTER 2 BOUTS OF DOWNHILL RUNNING

The purpose of this study was to compare blood markers associated with eccentrically biased exercise and muscle damage, after two bouts of d ownhill running. Nine active, untrained males performed 2 x 45 min bou ts of downhill running (- 0.16 radians), at a speed that would elicit 70% of each subjects (V) over dot O-2 max, on a level grade; runs were spaced 14 d apart (RUN1, RUN2), Blood samples were obtained before, a fter, and every hour for 12 h after exercise, as well as every 24 h fo r 5 d, to assess numbers of circulating neutrophils, monocytes, and ly mphocytes, serum cortisol, creatine kinase (CK); subjective sensations of delayed onset muscle soreness (DOMS) were monitored. To control fo r diurnal variation, two weeks prior to the RUN1, subjects had blood d raws performed at the same time as would occur after exercise, but did no exercise (CONTROL). During the 5 d after exercise, DOMS and CK wer e significantly greater (p < 0.05) after RUN1 compared to RUN2 and CON TROL. During the 12 h after RUN1 and RUN2, neutrophils showed similar responses compared to CONTROL. However, neutrophils were significantly elevated at 96 h after RUN1 and 24h after RUN2. Monocytes were signif icantly elevated during 5-11 h after RUN1 and RUN2, compared to CONTRO L. Cortisol showed a similar significant diurnal decrease for ail thre e conditions during the 12 h following exercise. The significantly low er levels of CK and DOMS seen after RUN2, compared with the initial ru n is consistent with the literature. The similar changes in neutrophil s and monocytes during the 12 h following RUN1 and RUN2, followed by d isparate responses over the subsequent 5 d, requires further investiga tion.