Serum Testosterone, Cortisol and Biochemistry During a Cycling Stage- Race

Abstract

0992 Previous research has characterized the effects of multi-day stage races on resting blood biochemistry and hormonal status in cyclists. Whether the effects of racing on markers of training stress are unique in those cyclists that achieve the highest overall rankings is unknown. PURPOSE: To compare common biochemical and hormone parameters used to monitor severity of exercise in cyclists placing top10 and those not placing top10 in a 6-D stage race. METHODS: Venous blood was collected on each race day (D1-D6) in the morning from 14 Australian male road cyclists competing in the Tour of Tasmania. Serum was analyzed for Creatine Kinase (CK), Urea and Urate using automated photometric techniques and serum Cortisol and Testosterone were quantified using a competitive immunoassay. Seven cyclists finished in the top 10 overall and 7 cyclists did not achieve a top 10 result. Plasma volume shifts were estimated based on hematocrit and hemoglobin concentration. Data were analyzed using a 2 × 6 (group × day) ANOVA with repeated measures over time and a series of unpaired t-tests to examine daily group differences. Data are presented as Mean ± SD. RESULTS: On D1 there were no significant differences between top 10 and non-top 10 finishers: CK (175 ± 88 vs 109 ± 28 IU.L−1, p = 0.08), Urea (6.2 ± 0.8 vs 5.8 ± 1.3 mM, p = 0.51), Urate (0.26 ± 0.4 vs 0.27 ± 0.4 mM, p = 0.52), Cortisol (409 ± 69 vs 439 ± 80 mM, p = 0.48), Testosterone (14.5 ± 6.1 vs 18.6 ± 10.5 mM, p = 0.39). Racing was associated with a significant decrease in Testosterone (−19%) and a significant increase in Plasma Volume (17%), Cortisol (25%), CK (70%), Urea (36%) and Urate (21%). Interestingly, cyclists placing top 10 had less of a plasma volume expansion (D3) and a greater increase in CK (D4-D6) and Cortisol (D5) than cyclists that did not achieve a top 10 result. Both top 10 and non-top 10 cyclists had a similar Urea, Urate and Testosteone response to racing. CONCLUSIONS: The higher concentration of serum CK and Cortisol in top10 cyclists may reflect that a greater relative effort is required to achieve a competitive result. Further research is needed to understand why resting CK and Cortisol, but not Urea, Urate or Testosterone are unique in cyclists placing well in a 6-day stage race.