Abstract
Exercise and carbohydrate (CHO) effects on cytokine changes in men, and to a lesser extent in women, are well described in the literature. However, there is a paucity of data describing such effects in girls. We previously reported differences in cytokine responses to exercise between boys and men, and hypothesized similar age-related differences in females. PURPOSE To determine the effects of high-intensity cycling and CHO intake on cytokine levels in girls. METHODS Thirteen 12-yr-old (YOUNG) and eleven 14-yr-old (OLD) girls participated. The older girls were taller (mean ± SD; 1.63 ± 0.05 vs. 1.57±0.07 m), heavier (58.3 ± 4.8 vs. 45.8 ± 7.8 kg), more advanced in pubertal development (2.9 ± 0.9 vs. 3.8 ± 0.6 for Tanner (T) staging of breast development), and had a higher % body fat (22.9 ± 5.2 vs. 18.1 ± 6.7 %). The two groups were matched for VO2max (51.7 ± 6.2 vs. 50.5 ± 4.3 mL−1 kg fat free mass1' min−1). On two occasions, each girl cycled for 60 min at 70% VO2max while intermittently drinking a 6% CHO drink or flavored water (FW). Venous blood samples were taken at rest (PRE), immediately after exercise (POST) and after 60 min of recovery (REC) to determine interleukin (IL)-6, IL-8 and TNF-α with R&D ELISA kits, reported as pg/mL. Estradiol levels at rest were also measured with RIA. RESULTS A main effect for exercise indicated higher IL-6 levels at POST and REC compared with PRE. Post-hoc analysis of a group × trial × time interaction indicated that the IL-6 level at REC in FW was higher in OLD (3.9 ± 2.9) compared with YOUNG (1.9 ± 1.1). However, when IL-6 was analyzed according to pubertal status, this interaction disappeared. A main effect for exercise indicated higher IL-8 levels at POST (6.2 ± 3.5) and REC (8.7 ± 4.3) compared with PRE (4.4 ± 1.9) and at REC compared with POST. When IL-8 was analyzed according to pubertal status, a post-hoc analysis of a group × time interaction revealed that IL-8 increased at POST compared with PRE in T3, but not T2 or T4-5. However, REC levels were higher than PRE in T2 and T4-5, but not T3. CHO had more of an impact on the IL-6 than the IL-8 response to exercise. There was no effect of exercise, CHO, age, or pubertal status on TNF-α levels, which remained at ∼1.0 pg/mL. All correlation analyses were performed on values from FW and revealed that resting estradiol levels were not related to REC levels of IL-6 (r=−0.01, p=0.95), but were significantly related to REC IL-8 (r=0.43, p=0.04). CONCLUSION These results indicate a differential response of IL-6 and IL-8 to high-intensity exercise in girls, which may be associated with maturity status. Supported by the Gatorade Sports Science Institute.
Published Version
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