Effects of heavy endurance physical exercise on inflammatory markers in non-athletes

Physical activity has beneficial effects on cardiovascular disease but the mechanisms are still somewhat unclear. One possible pathway may be through the anti-inflammatory effects attributed to regular physical activity. Our primary aim was to study the effects of endurance physical exercise on C-reactive protein (CRP), Interleukin-6 (IL-6), Tumor Necrosis Factor-alpha (TNFalpha) during the acute and recovery phases. Secondarily, we studied the impact of diet on these inflammatory markers.

Twenty men, aged 18-55 years, participated in a 14 days cross-country skiing tour. They traveled 12-30km per day corresponding to about 10h of heavy physical activity. The participants were randomized to a diet with either 30 or 40% of energy derived from fat. Inflammatory variables were analysed at week 0, after 1 and 2 weeks and during the recovery phase at week 6 and 8.

CRP and TNFalpha increased significantly during the two weeks of exercise (1.4-5.0mg/l, p=0.00 and 6.8-8.4pg/ml, p=0.00). CRP levels were significantly lower during recovery (median 0.7mg/l) compared to baseline (median 1.4mg/l) and did not correlate to metabolic variables. There were no significant changes in IL-6 levels during the study period. For dietary groups significant CRP changes were observed only in the high fat group during recovery.

CRP and TNFalpha increased significantly but reacted differently during heavy physical activity while there seemed to be no significant changes in IL-6. No significant differences regarding inflammatory variables were found between the dietary groups.