1. Altered muscle strength and architecture influences motor performance in boys with severe haemophilia and ankle joint haemarthrosis David Stephensen 1,2, Wendy Drechsler 1, Oona Scott 1 1 Human Motor Performance Laboratory, School of Health, Sport & Bioscience University of East London 2 Kent Haemophilia Centre, Kent & Canterbury Hospital

2. Haemophilia  Deficiency of factor 8 (haemophilia A) or factor 9 (Haemophilia B / Christmas disease)  X linked recessive  Presents before 1 year of age

3. Haemophilia  Deficiency of factor 8 (haemophilia A) or factor 9 (Haemophilia B / Christmas disease)  X linked recessive  Presents before 1 year of age  Recurrent frequent spontaneous bleeding into muscles and joints  Results in chronic disabling arthropathy

4. Background  Annual bleed frequency of 1-2 bleeds / yr (Feldmen et al. 2006; Manco-Johnson et al. 2007; Gringeri et al. 2011)  Ankle joint is the most common site of bleeding (Stephensen et al. 2009)  Muscles are smaller and weaker than their unaffected peers (Stephensen et al., 2012)  Alterations in balance and gait when compared to unaffected peers (Bladen et al. 2007; Stephensen et al. 2009; De Souza et al., 2012)

5. Aim of the study Relationship of lateral gastrocnemius muscle architecture to:  Ankle plantar flexor muscle strength  Knee and ankle function

6. Participants Haemophilic boys were receiving prophylactic treatment and had a history of only ankle joint bleeding

7. Methodology  Muscle architecture  Anatomical cross sectional area (ACSA)  Thickness (MT) and width (MW)  Muscle fascicle length (FL) and pennation angle (PA)  Isokinetic muscle strength  Three-dimensional joint angles and moments

8. Three-dimensional joint angles and moments

9. Initial Double Support Single Support Terminal Double Support Swing

10. *p<0.05; **p<0.01; ***p<0.005 Results

11. *p<0.05; **p<0.01; ***p<0.005 Results

12. *p<0.05; **p<0.01; ***p<0.005 Results

13. 5 10 15 20 25 0204060 Muscle strength (Nm) Muscle thickness (mm) 300 400 500 600 700 800 0204060 Muscle strength (Nm) ACSA (mm 2 ) TD: r = 0.43 H: r = 0.06 TD: r = 0.35 H: r = 0.53 Muscle strength is related to muscle size

14. 0.0 0.5 1.0 1.5 0.000.050.10 Specific muscle torque (Nm/mm 2 ) Knee flexion moment (Nm/kg) H: r = -0.61 (p < 0.05) TD: r = -0.32

15. 0.0 0.5 1.0 1.5 304050607080 Fascicle length (mm) Knee flexion moment (Nm/kg) TD: r = 0.24 H: r = -0.58 (p < 0.05) 10 11 12 13 14 15 0204060 Muscle strength (Nm) Maximum GRF (N/kg) H: r = -0.59 (p < 0.05) TD: r = -0.45

16. -0.1 0.0 0.1 0.2 0.3 0.000.050.10 Specific muscle torque (Nm/mm 2 ) Ankle dorsiflexion moment (Nm/kg) 0 10 20 30 510152025 Muscle thickness (mm) Ankle plantarflexion ( 0 ) TD: r = -0.13 H: r = 0.52 (p < 0.05) TD: r = 0.13 H: r = -0.46 (p < 0.05)

17. Clinical significance  Importance of evaluating muscle function and strength  Ankle plantar flexors are weaker and smaller  Muscle strength and architecture strongly influence gait adaptations  Impacts ankle and knee joint function during weight-bearing phases of walking

18. Acknowledgements (NIHR) National Institute for Health Research NHS d.stephensen@uel.ac.uk