Skeletal muscle-derived interleukin-6 (IL-6) is a pleiotropic cytokine which regulates body metabolism during strenuous physical exercise. OBJECTIVE: The effect of a potentially functional single nucleotide polymorphism (SNP) -174G/C of the IL6 gene (rs1800795) promoter was examined on maximal oxygen uptake (VO₂max), body mass index (BMI) and plasma IL-6 levels in response to physical training. Fifty four male military conscripts were studied for 8 weeks during their basic training. At weeks 1, 5 and 8, VO₂max and anthropometrics were measured, and blood samples collected before and after acute aerobic exercise. Acute exercise increased plasma IL-6 in subjects with genotype CG. Moreover, during the 8-week training period, a tendency for increased plasma IL-6 was observed in subjects with this genotype. VO₂max values increased in all genotype groups, but subjects with genotype CG made the greatest gains in VO₂max. Training significantly decreased BMI only in subjects with genotype CG. Our findings suggest that the allele C may have an effect on plasma IL-6 response to acute exercise in healthy male subjects. Exercise training has a favourable effect on VO₂max and BMI, with the most prominent effects in subjects with genotype CG. Thus we conclude that this SNP may account for individual response to exercise training.

• Allele C of the IL6 promoter SNP -174G/C may have an effect on plasma IL-6 response to acute exercise.

• All subjects responded to physical exercise, but the improvement in VOmax and decrease in BMI after training are more pronounced in the individuals with genotype CG, hence the IL6 promoter SNP -174G/C may have an influence on training responses.

• The small number of subjects investigated in the present study warrants further research to confirm these findings in large cohorts.