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Cytokine Responses to Treadmill Running in Healthy and Illness-Prone Athletes


Medicine & Science in Sports & Exercise: November 2007 - Volume 39 - Issue 11 - p 1918-1926
doi: 10.1249/mss.0b013e318149f2aa
CLINICAL SCIENCES: Clinically Relevant

Purpose: To characterize differences in cytokine responses to exercise of different intensities and durations between healthy and illness-prone runners.

Methods: Trained distance runners were classified as healthy (no more than two episodes of upper-respiratory symptoms per year; N = 10) or illness-prone (four or more episodes per year; N = 8) and completed three treadmill tests: SHORT (30 min, 65% V˙O2max), LONG (60 min, 65% V˙O2max), and INTENSE (6 × 3 min, 90% V˙O2max). Blood samples were collected pre-, post-, 1 h, 10 h, and 24 h after exercise, and interleukin (IL)-2, IL-4, IL-6, IL-8, IL-10, IL-12, and IL-1ra concentrations were determined. Repeated-measures ANOVA was used to assess changes in cytokine responses to exercise. Magnitudes of changes and differences between groups were characterized using Cohen's effect size (ES) criteria.

Results: Resting IL-8, IL-10, and IL-1ra concentrations were 19-38% lower (ES:0.38-0.96; small to moderate differences) in illness-prone runners. Similarly, postexercise IL-10 concentrations were 13-20% lower (ES: 0.20-0.37; small differences), and IL-1ra concentrations were 10-20% lower (ES: 0.22-0.38; small differences) in illness-prone subjects. In contrast, IL-6 elevations were 84-185% higher (ES: 0.29-0.59, small differences) in illness-prone subjects. Postexercise responses of IL-2, IL-4, and IL-12 were small and not substantially different between the groups.

Conclusions: Cytokine responses to controlled treadmill running differ between healthy and illness-prone athletes. Illness-prone distance runners showed evidence suggestive of impaired inflammatory regulation in the hours after exercise that may account for the greater frequency of upper-respiratory symptoms experienced.

1Department of Physiology, Australian Institute of Sport, Canberra, AUSTRALIA; 2School of Biomedical Sciences, Faculty of Health, University of Newcastle, Callaghan, AUSTRALIA; and 3Medical School, The Australian National University, Canberra, AUSTRALIA

Address for correspondence: Ms. Amanda Cox, Department of Physiology, Australian Institute of Sport, PO Box 176, Belconnen ACT 2616, Australia; E-mail:

Submitted for publication January 2007.

Accepted for publication June 2007.

©2007The American College of Sports Medicine