Background: Circadian rhythm and physical activity are
factors that influence the homeostasis of blood. This study aimed to
investigate the effect of exhaustive exercise in the morning and evening on the
blood hemostasis in female athletes.
Methods: In the present quasi-experimental study, 30
female athletes aged 18-25 were selected by convenience sampling method and
randomly divided into two groups (morning and afternoon exercises). The
standard Bruce protocol test was used. In the present study, platelets,
fibrinogen, and thromboplastin time were measured as indicators of blood
coagulation before and after testing. Paired t-test and covariance analysis
were used to analyze the measured indices and P ≤ 0.05 was considered
Results: An acute exhausting aerobic training session in
both groups significantly increased platelet and fibrinogen levels, but a
significant decrease was observed in thromboplastin time. Considering the
training time, significant difference was observed in the blood thromboplastin
time in the morning in comparison with the afternoon.
Conclusion: According to the results of this study, the
circadian rhythm and acute exhausting aerobic training are effective factors on
the blood coagulation and a training session in the morning compared with the
evening training has a greater effect on the blood coagulation.