Related Experiment Video
Updated: Jul 29, 2025

Tail Vein Transection Bleeding Model in Fully Anesthetized Hemophilia A Mice
Published on: September 30, 2021
Clotting factor activity levels and bleeding risk in people with haemophilia playing sports
Olav Versloot1,2, Ellen Kemler3, Johan Blokzijl1
1Centre for Benign Haematology, Thrombosis and Haemostasis, Van Creveldkliniek, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands.
Background:
Improved treatment options for people with haemophilia (PWH) have increased the possibilities for sports participation, but the risk of sports-induced bleeding (SIB) is still considered considerable by many.
Aim:
To assess sports associated injury- and bleeding risk in PWH and to assess clotting levels associated with safe sports participation.
Methods:
Sports injuries and SIBs were prospectively collected for 12 months in PWH aged 6-49 without inhibitors playing sports at least once weekly. Injuries were compared according to factor levels, severity, joint health, sports risk category and sports intensity. Factor activity at the time of injury was estimated using a pharmacokinetic model.
Results:
125 participants aged 6-49 (41 children, 90% haemophilia A; 48% severe, 95% severe on prophylaxis) were included. Sports injuries were reported by 51 participants (41%). Most participants (62%) reported no bleeds at all and only 16% reported SIBs. SIBs were associated with factor levels at time of injury (OR: 0.93/%factor level (CI 0.88-0.99); p = .02), but not with haemophilia severity (OR: 0.62 (CI 0.20-1.89); p = .40), joint health, sports risk category or sports intensity. PWH with factor levels <10% during sports injury had a bleeding risk of 41% versus 20% in those with higher (>10%) factor levels.
Conclusion:
The results of this study emphasize the importance of clotting factor levels in prevention of bleeds. This information is vital for patient counselling and tailoring prophylactic treatment with clotting factors and non-replacement therapy.
Related Concept Videos
Disorders of Hemostasis
Thromboembolic Disorders
Two factors primarily cause thromboembolic conditions.
Extrinsic and Intrinsic Pathways of Hemostasis
The Extrinsic Pathway
The extrinsic pathway of coagulation is typically initiated by tissue damage that exposes blood to tissue factor (TF), a protein released by the damaged tissue cells outside the blood vessels—this interaction with TF triggers biochemical reactions involving specific clotting factors. The key player here is Factor VII, which...
Anticoagulant Drugs: Low-Molecular-Weight Heparins
Clot Retraction and Fibrinolysis
Coagulation
During the coagulation phase, clotting factors, or procoagulants, play a vital role in initiating and progressing the coagulation cascade. This cascade is a series of reactions...
Introduction to Hemostasis
The three phases of hemostasis involve many clotting factors present in plasma and several substances released by platelets and injured tissue cells. It is a fast, localized,...

