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The Journal of Sports Medicine and Physical Fitness 2020 Oct 22

DOI: 10.23736/S0022-4707.20.11174-5

Copyright © 2020 EDIZIONI MINERVA MEDICA

language: English

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

Roman ALBERTY 1 , Martin PUPIŠ 2, Vladimír VACHALÍK 3, Miloš BÁTOVSKY

1 Department of Biology and Ecology, Matej Bel University, Banská Bystrica, Slovakia; 2 Department of Physical Education and Sports, Matej Bel University, Banská Bystrica, Slovakia; 3 Diagnostic Laboratory, Military Sports Centre Dukla, Banská Bystrica, Slovakia


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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: 10 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. Haemoglobin (Hb), haematocrit (Hct), and the reticulocytes % (Ret%) were determined by flow cytometry. Changes in OFF-hr score were also calculated and repeatedmeasures ANOVA was used to compare diurnal differences.
RESULTS: In overall, the mean Hb decreased continuously by 4.5 and 3.3% (all P < 0.001) over the day with single and repeated bouts of exercise, respectively. Corresponding values for the decline in Hct were 4.2 and 5.9% (all P < 0.001). In contrast, the Ret% showed no apparent diurnal rhythm but single and repeated bouts of exercise increased the relative Ret% in the evening by 12.4 and 16.7% (P < 0.01), respectively. Then the calculated OFF-hr score was reduced by 6.2 and 9.8% (all P < 0.01) at the end of the day.
CONCLUSIONS: These results confirmed the normal diurnal pattern in the examined red blood cell variables in response to exercise in highly trained athletes. Furthermore, they showed noticeable between-subject variability and the possible risk of a false suspicion of blood doping in undoped athletes after repeated bouts of exercise.


KEY WORDS: Blood doping; Sports; Training load; Haematology; Circadian variation

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