Thyroid hormones response in simulated laboratory sprint duathlon
Increased activity of the pituitary-thyroid axis, plays a role in adaptations to exercise. The aim of this study was to assess changes in thyroid hormones (TH) in a simulated laboratory competition of sprint duathlon. Eight duathletes trained males [mean (SD), age 24.8 (6.8) years, height 174.4 (6.8) cm, body mass 67.12 (8.1) kg] participate in this study. The duathletes performed two graded maximal exercise in random order, one on cycle-ergometer and other on a treadmill, to determine their VO2peak. Simulated laboratory competition was carried out during 20 min Run1, 40 min Bike and 12 min Run2 sectors. A blood sample was drawn to determine serum concentrations of TSH, T4, T3 and were analyzed by chemiluminiscence. A one-way analysis of variance (ANOVA) was used to analyze differences among sectors and Pearson correlation coefficients were calculated between TH and exercise intensity. Athletes perform a high intensity exercise reaching high mean values of aerobic power (89.6 ± 6.1, 85.1 ± 8.7 and 87.1 ± 6.9 of %VO2 in Run1, Bike and Run2 respectively). TSH shown differences between -30 min and Run2 (p< 0.05), and did not found changes in T3 and T4 during exercise (p>0.05). Significant inverse correlations between T3 (r= -0.86) and T4 (r= -0.86) and percent VO2 (p
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