Children with cerebral palsy present early in the childhood altered muscular properties, as soon as structural or stiffness. In the gastrocnemius muscle, altered muscular properties are characterized by short muscle belly length and increased stiffness which contribute to contracture and limiting joint range of motion. This study assess efficacy of an acute high intensity and long-time stretching session of plantarflexors muscle on their viscoelasticity properties and maximal dorsiflexion angle gain. Single stretching session is characterized by high intensity and long time (5 minutes).

Inclusion Criteria:

• Children with cerebral palsy of the spastic type
• Children with a maximum dorsal ankle flexion amplitude limitation of less than 10°.

Exclusion Criteria:

• Children who have undergone surgery on the lower limbs.
• Children with a botulinum toxin injection and/or a series of elongation casts for less than three months.
• Children with ongoing analgesic treatment