Serum Bilirubin Concentrations and the Prevalence of Gilbert Syndrome in Elite Athletes.

Objectives: Bilirubin is a potent endogenous antioxidant and immunomodulating substance, which is also implicated in both cell signalling and various metabolic pathways. Mild elevation of systemic bilirubin concentrations provides substantial protection against many diseases of civilization. Rare published reports have suggested that serum bilirubin might also be relevant to sports performance.

Diurnal variation in red blood cell variables in athletes after single and repeated bouts of exercise.

Background: The aim of this study was to examine the diurnal and exercise-related changes in red blood cell variables which serve as indirect markers of doping in sports.

Methods: Ten men and 7 women, all undoped highly trained endurance athletes aged 19-34 years, were included in the study. Before and on the day with single and repeated bouts of exercise, blood samples were collected at 07:00, 09:00, 13:00, 18:00, and 21:00, at least 2 hours after exercise.