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n South African Journal of Sports Medicine - Changes in neutrophil count, creatine kinase and muscle soreness after repeated bouts of downhill running : original research article
Objective. A primary objective was to examine circulating neutrophil count after repeated bouts of downhill running. An additional aim was to determine creatine kinase (CK) levels during the initial 12 hours, after repeated DHRs.
Design. Eleven healthy, untrained Caucasian males performed 2 x 60 min bouts of DHR (-13.5%), spaced 14 days apart, at a speed equal to 75% VO2max on a level grade. Blood was collected before, after, and every hour for 12 hours, and every 24 hours for 6 days. Absolute neutrophil count, CK, and delayed-onset muscle soreness (DOMS) were assessed. Results were analysed using repeated measures ANOVA (p<0.05) with appropriate post hoc tests.
Results. There were no significant differences in neutrophil count (p=0.24) during the 12-h period following run 1 (mean±se, 6.45±0.29 10-9.l-1) versus run 2 (5.96±0.09 10-9.l-1), or during the 24-h periods for run 1 (3.48±0.09 10-9.l-1) or run 2 (3.47±0.09 10-9.l-1). During the initial 12-h period, there was a significant interaction effect (p=0.0001) for CK with differences between bouts seen between 3 - 12 h; differences remained evident at 24 h and at 96 - 144 h. In all muscle groups, DOMS was significantly lower after run 2 compared with run 1.
Conclusion. The lack of significance in neutrophils, as well as the early onset of difference in CK between run 1 and run 2 were attributed to the type of eccentric protocol used. It was proposed that future studies be more cognisant of whether the eccentric mode is predominantly low-intensity long-duration or high-intensity short-duration.
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