Table 1 Inclusion and exclusion criteria

Children must have:

1. a clinical diagnosis of unilateral or bilateral spastic CP

2. an age between 4-12 years old

3. at least 0° ankle dorsiflexion with extended knee (physical examination)

4. a GMFCS class I, II or III

5. has been treated for reduced ankle dorsiflexion (< 5° dorsiflexion) before the start of the study by:

a. and/or serial casting at least 3 months ago

b. and/or botulinum toxin A injections in the Gastrocnemius and/or Soleus muscle at least 6 months ago

c. orthotic management in rest with a knee-ankle-foot orthosis to prevent for decreasing ankle dorsiflexion

6. a stable social family situation

Children must not:

1. have had surgery of the Gastrocnemius and/or Soleus muscle

2. have had Selective Dorsal Rhizotomy

3. have had Intrathecal Baclofen therapy

4. have had Botulinum toxin A treatment in the lower extremity less than 6 months ago

5. have had casting of the lower extremity less than 3 months ago

6. have knee contractures (less than 0° knee extension)

7. have more than 20° ankle dorsiflexion at full knee extension

8. have behavioural problems (like severe mental retardation)

9. have significant sleeping problems

10. be institutionalised

11. be suffering from co-morbidity interfering with mobility that prevents them from walking adequate distance.

12. have problems with understanding either the Dutch (for subjects in the Netherlands) or English language