J. W. Lance, The control of muscle tone, reflexes, and movement: Robert Wartenberg Lecture, Neurology, vol.30, issue.12, pp.1303-1313, 1980.

O. Simon and A. P. Yelnik, Managing spasticity with drugs, Eur J Phys Rehabil Med, vol.46, issue.3, pp.401-410, 2010.

M. Nozoe, H. Kubo, and A. Furuichi, Validity of Quadriceps Muscle Thickness Measurement in Patients with Subacute Stroke during Hospitalization for Assessment of Muscle Wasting and Physical Function, J Stroke Cerebrovasc Dis Off J Natl Stroke Assoc, vol.26, issue.2, pp.438-441, 2017.

L. R. Smith, H. G. Chambers, S. Subramaniam, and R. L. Lieber, Transcriptional abnormalities of hamstring muscle contractures in children with cerebral palsy, PloS One, vol.7, issue.8, p.40686, 2012.

L. R. Smith, E. Pontén, and Y. Hedström, Novel transcriptional profile in wrist muscles from cerebral palsy patients, BMC Med Genomics, vol.2, p.44, 2009.

V. Dietz, T. Sinkjaer, and . Spasticity, Handb Clin Neurol, vol.109, pp.197-211, 2012.

C. Gans and W. J. Bock, The functional significance of muscle architecture--a theoretical analysis, Ergeb Anat Entwicklungsgesch, vol.38, pp.115-142, 1965.

T. Kardel, Willis and Steno on muscles: rediscovery of a 17th-century biological theory, J Hist Neurosci, vol.5, issue.2, pp.100-107, 1996.

R. L. Lieber, S. Steinman, I. A. Barash, and H. Chambers, Structural and functional changes in spastic skeletal muscle, Muscle Nerve, vol.29, issue.5, pp.615-627, 2004.

B. Parratte, L. Tatu, F. Vuillier, M. Diop, and G. Monnier, Intramuscular distribution of nerves in the human triceps surae muscle: anatomical bases for treatment of spastic drop foot with botulinum toxin, Surg Radiol Anat SRA, vol.24, issue.2, pp.91-96, 2002.

J. Foran, S. Steinman, I. Barash, H. G. Chambers, and R. L. Lieber, Structural and mechanical alterations in spastic skeletal muscle, Dev Med Child Neurol, vol.47, issue.10, pp.713-717, 2005.

M. De-bruin, M. J. Smeulders, M. Kreulen, P. A. Huijing, and R. T. Jaspers, Intramuscular Connective Tissue Differences in Spastic and Control Muscle: A Mechanical and Histological Study. Sampaolesi M, vol.9, p.101038, 2014.

M. A. Mathewson, H. G. Chambers, P. J. Girard, M. Tenenhaus, A. K. Schwartz et al., Stiff muscle fibers in calf muscles of patients with cerebral palsy lead to high passive muscle stiffness: CP CALF MUSCLE FIBER STIFFNESS, J Orthop Res, vol.32, issue.12, pp.1667-1674, 2014.

V. S. Dubowitz, Muscle biopsy : a practical approach, Philadelphia: Saunders, 2007.

M. E. Castle, T. A. Reyman, and M. Schneider, Pathology of spastic muscle in cerebral palsy, Clin Orthop, issue.142, pp.223-232, 1979.

S. Dayanidhi, P. B. Dykstra, V. Lyubasyuk, B. R. Mckay, H. G. Chambers et al., Reduced satellite cell number in situ in muscular contractures from children with cerebral palsy: REDUCED SATELLITE CELLS IN SITU, J Orthop Res, vol.33, issue.7, pp.1039-1045, 2015.

C. M. Booth, M. J. Cortina-borja, and T. N. Theologis, Collagen accumulation in muscles of children with cerebral palsy and correlation with severity of spasticity, Dev Med Child Neurol, vol.43, issue.5, pp.314-320, 2001.

J. Ito, A. Araki, H. Tanaka, T. Tasaki, K. Cho et al., Muscle histopathology in spastic cerebral palsy, Brain Dev, vol.18, issue.4, pp.299-303, 1996.

M. Sjöström, A. R. Fugl-meyer, G. Nordin, and L. Wählby, Post-stroke hemiplegia; crural muscle strength and structure, Scand J Rehabil Med Suppl, vol.7, pp.53-67, 1980.

F. Gao, T. H. Grant, E. J. Roth, and L. Zhang, Changes in Passive Mechanical Properties of the Gastrocnemius Muscle at the Muscle Fascicle and Joint Levels in Stroke Survivors, Arch Phys Med Rehabil, vol.90, issue.5, pp.819-826, 2009.

R. S. Barrett and G. A. Lichtwark, Gross muscle morphology and structure in spastic cerebral palsy: a systematic review: Gross Muscle Morphology and Structure in CP, Dev Med Child Neurol, vol.52, issue.9, pp.794-804, 2010.

A. A. Mohagheghi, T. Khan, T. H. Meadows, K. Giannikas, V. Baltzopoulos et al., Hamstring contractures in children with spastic cerebral palsy result from a stiffer extracellular matrix and increased in vivo sarcomere length: Passive mechanical properties of muscle contracture, Clin Biomech, vol.22, issue.6, pp.2625-2639, 2007.

E. M. Mclachlan, Atrophic effects of proximal tendon transection with and without denervation on mouse soleus muscles, Exp Neurol, vol.81, issue.3, pp.651-668, 1983.

P. E. Williams and G. Goldspink, Changes in sarcomere length and physiological properties in immobilized muscle, J Anat, vol.127, pp.459-468, 1978.

L. Barber, T. Hastings-ison, R. Baker, R. Barrett, and G. Lichtwark, Medial gastrocnemius muscle volume and fascicle length in children aged 2 to 5 years with cerebral palsy: Muscle Morphology in Children with Spastic CP, Dev Med Child Neurol, vol.53, issue.6, pp.543-548, 2011.

J. Fridén and R. L. Lieber, Spastic muscle cells are shorter and stiffer than normal cells, Muscle Nerve, vol.27, issue.2, pp.157-164, 2003.

N. Theis, A. A. Mohagheghi, and T. Korff, Mechanical and material properties of the plantarflexor muscles and Achilles tendon in children with spastic cerebral palsy and typically developing children, J Biomech, vol.49, issue.13, pp.3004-3008, 2016.

E. Huet-de-la-tour, C. Tardieu, J. C. Tabary, and C. Tabary, Decrease of muscle extensibility and reduction of sarcomere number in soleus muscle following a local injection of tetanus toxin, J Neurol Sci, vol.40, issue.2-3, pp.123-131, 1979.

J. Crosbie, A. Alhusaini, C. M. Dean, and R. B. Shepherd, Plantarflexor muscle and spatiotemporal gait characteristics of children with hemiplegic cerebral palsy: an observational study, Dev Neurorehabilitation, vol.15, issue.2, pp.114-118, 2012.

A. P. Yelnik, O. Simon, and D. Bensmail, Drug treatments for spasticity, Ann Phys Rehabil Med, vol.52, issue.10, pp.746-756, 2009.

J. A. Baker and G. Pereira, The efficacy of Botulinum Toxin A for limb spasticity on improving activity restriction and quality of life: a systematic review and meta-analysis using the GRADE approach, Clin Rehabil, vol.30, issue.6, pp.549-558, 2016.

J. Gracies, Pathophysiology of spastic paresis. I: Paresis and soft tissue changes, Muscle Nerve, vol.31, issue.5, pp.535-551, 2005.

E. J. Moore, M. Banky, J. Olver, A. L. Bryant, and G. Williams, The effectiveness of therapy on outcome following (BoNT-A) injection for focal spasticity in adults with neurological conditions: A systematic review, Brain Inj, vol.29, issue.6, pp.676-687, 2015.

E. M. Simoneau, S. Longo, O. R. Seynnes, and M. V. Narici, Human muscle fascicle behavior in agonist and antagonist isometric contractions, Muscle Nerve, vol.45, issue.1, pp.92-99, 2012.

C. N. Maganaris, Force-length characteristics of the in vivo human gastrocnemius muscle, Clin Anat, vol.16, issue.3, pp.215-223, 2003.

I. S. Raj, S. R. Bird, and A. J. Shield, Reliability of ultrasonographic measurement of the architecture of the vastus lateralis and gastrocnemius medialis muscles in older adults: Reliability of ultrasonography, Clin Physiol Funct Imaging, vol.32, issue.1, pp.65-70, 2012.

K. Legerlotz, H. K. Smith, and W. A. Hing, Variation and reliability of ultrasonographic quantification of the architecture of the medial gastrocnemius muscle in young children, Clin Physiol Funct Imaging, vol.30, issue.3, pp.198-205, 2010.

E. M. Strasser, T. Draskovits, M. Praschak, M. Quittan, and A. Graf, Association between ultrasound measurements of muscle thickness, pennation angle, echogenicity and skeletal muscle strength in the elderly, AGE, vol.35, issue.6, pp.2377-2388, 2013.

Y. Kawakami, T. Abe, and T. Fukunaga, Muscle-fiber pennation angles are greater in hypertrophied than in normal muscles, J Appl Physiol Bethesda Md, vol.74, issue.6, pp.2740-2744, 1985.

E. S. Park, D. Rha, J. K. Yoo, S. M. Kim, W. H. Chang et al., Short-term effects of combined serial casting and botulinum toxin injection for spastic equinus in ambulatory children with cerebral palsy, Yonsei Med J, vol.51, issue.4, pp.579-584, 2010.

T. Bandholm, S. Sonne-holm, C. Thomsen, J. Bencke, S. A. Pedersen et al., Calf muscle volume estimates: implications for botulinum toxin treatment?, Pediatr Neurol, vol.37, issue.4, pp.263-269, 2007.

M. Miyatani, H. Kanehisa, M. Ito, Y. Kawakami, and T. Fukunaga, The accuracy of volume estimates using ultrasound muscle thickness measurements in different muscle groups, Eur J Appl Physiol, vol.91, issue.2-3, pp.264-272, 2004.

D. Mayans, M. S. Cartwright, F. O. Walker, A. Picelli, S. Tamburin et al., Relationship Between Ultrasonographic, Electromyographic, and Clinical Parameters in Adult Stroke Patients With Spastic Equinus: An Observational Study, Phys Med Rehabil Clin N Am, vol.23, issue.1, pp.1564-1570, 2012.

C. M. Zaidman, M. R. Holland, M. J. Noetzel, T. S. Park, and A. Pestronk, Newborn brachial plexus palsy: evaluation of severity using quantitative ultrasound of muscle, Muscle Nerve, vol.47, issue.2, pp.246-254, 2013.

T. Deffieux, J. Gennisson, B. Larrat, M. Fink, and M. Tanter, The variance of quantitative estimates in shear wave imaging: Theory and experiments, IEEE Trans Ultrason Ferroelectr Freq Control, vol.59, issue.11, 2012.

J. Bercoff, M. Tanter, and M. Fink, Supersonic shear imaging: a new technique for soft tissue elasticity mapping, Ultrason Ferroelectr Freq Control IEEE Trans On, vol.51, issue.4, pp.396-409, 2004.

L. Lacourpaille, F. Hug, K. Bouillard, J. Hogrel, and A. Nordez, Supersonic shear imaging provides a reliable measurement of resting muscle shear elastic modulus, Physiol Meas, vol.33, issue.3, pp.19-28, 2012.

O. Maïsetti, F. Hug, K. Bouillard, and A. Nordez, Characterization of passive elastic properties of the human medial gastrocnemius muscle belly using supersonic shear imaging, J Biomech, vol.45, issue.6, pp.978-984, 2012.

A. Nordez, A. Guével, P. Casari, S. Catheline, and C. Cornu, Assessment of muscle hardness changes induced by a submaximal fatiguing isometric contraction, J Electromyogr Kinesiol, vol.19, issue.3, pp.484-491, 2009.
URL : https://hal.archives-ouvertes.fr/hal-01005278

K. H. Cho, H. J. Lee, and W. H. Lee, Reliability of rehabilitative ultrasound imaging for the medial gastrocnemius muscle in poststroke patients, Clin Physiol Funct Imaging, vol.34, issue.1, pp.26-31, 2014.

M. K. Chakouch, P. Pouletaut, F. Charleux, and S. F. Bensamoun, Viscoelastic shear properties of in vivo thigh muscles measured by MR elastography, J Magn Reson Imaging JMRI, vol.43, issue.6, pp.1423-1433, 2016.

M. F. Gordon, A. Brashear, and E. Elovic, Repeated dosing of botulinum toxin type A for upper limb spasticity following stroke, Neurology, vol.63, issue.10, pp.1971-1973, 2004.

J. Valentine, K. Stannage, and V. Fabian, Muscle histopathology in children with spastic cerebral palsy receiving botulinum toxin type A: BoNTA and Muscle Histopathology, Muscle Nerve, vol.53, issue.3, pp.407-414, 2016.

S. A. Williams, C. Elliott, J. Valentine, A. Gubbay, P. Shipman et al., Combining strength training and botulinum neurotoxin intervention in children with cerebral palsy: the impact on muscle morphology and strength, Disabil Rehabil, vol.35, issue.7, pp.596-605, 2013.

L. Mathevon, F. Michel, P. Decavel, B. Fernandez, B. Parratte et al., Muscle structure and stiffness assessment after botulinum toxin type A injection. A systematic review, Ann Phys Rehabil Med, vol.58, issue.6, pp.343-350, 2015.

N. Dursun, T. Gokbel, M. Akarsu, and E. Dursun, Randomized Controlled Trial on Effectiveness of Intermittent Serial Casting on Spastic Equinus Foot in Children with Cerebral Palsy After Botulinum Toxin-A Treatment, Am J Phys Med Rehabil, vol.96, issue.4, pp.221-225, 2017.

R. M. Kay, S. A. Rethlefsen, A. Fern-buneo, T. Wren, and D. L. Skaggs, Botulinum toxin as an adjunct to serial casting treatment in children with cerebral palsy, J Bone Joint Surg Am, vol.86, issue.11, pp.2377-2384, 2004.

J. D. Ackman, B. S. Russman, and S. S. Thomas, Comparing botulinum toxin A with casting for treatment of dynamic equinus in children with cerebral palsy, Dev Med Child Neurol, vol.47, issue.9, pp.620-627, 2005.

S. Hayek, G. A. Wientroub, S. Yizhar, and Z. , The effect of injections of botulinum toxin type A combined with casting on the equinus gait of children with cerebral palsy, J Bone Joint Surg Br, vol.92, issue.8, pp.1152-1159, 2010.

A. Elvrum, S. M. Braendvik, R. Saether, T. Lamvik, B. Vereijken et al., Effectiveness of resistance training in combination with botulinum toxin-A on hand and arm use in children with cerebral palsy: a pre-post intervention study, BMC Pediatr, vol.12, p.91, 2012.

P. B. Mills, H. Finlayson, M. Sudol, O. Connor, and R. , Systematic review of adjunct therapies to improve outcomes following botulinum toxin injection for treatment of limb spasticity, Clin Rehabil, vol.30, issue.6, pp.537-548, 2016.

D. Dressler, G. Dirnberger, and K. P. Bhatia, Botulinum toxin antibody testing: comparison between the mouse protection assay and the mouse lethality assay, Mov Disord Off J Mov Disord Soc, vol.15, issue.5, pp.973-976, 2000.

R. Katz and E. Pierrot-deseilligny, Recurrent inhibition of alpha-motoneurons in patients with upper motor neuron lesions, Brain J Neurol, vol.105, pp.103-124, 1982.

E. J. Sobolewski, E. D. Ryan, and B. J. Thompson, Influence of maximum range of motion and stiffness on the viscoelastic stretch response, Muscle Nerve, vol.48, issue.4, pp.571-577, 2013.

M. C. Bilgici, T. Bekci, and Y. Ulus, Quantitative assessment of muscular stiffness in children with cerebral palsy using acoustic radiation force impulse (ARFI) ultrasound elastography, J Med Ultrason, 2001.

M. Mansouri, P. M. Birgani, M. R. Kharazi, M. Lotfian, M. Naeimipoor et al., Estimation of gait parameter using sonoelastography in children with cerebral palsy, Conf Proc Annu Int Conf IEEE Eng Med Biol Soc IEEE Eng Med Biol Soc Annu Conf, vol.2016, pp.1729-1732, 2016.

A. Boyaci, A. Tutoglu, and N. Boyaci, Changes in spastic muscle stiffness after botulinum toxin A injections as part of rehabilitation therapy in patients with spastic cerebral palsy, NeuroRehabilitation, vol.35, issue.1, pp.123-129, 2014.

D. R. Kwon, G. Y. Park, and J. G. Kwon, The change of intrinsic stiffness in gastrocnemius after intensive rehabilitation with botulinum toxin a injection in spastic diplegic cerebral palsy, Ann Rehabil Med, vol.36, issue.3, pp.400-403, 2012.

K. L. Jakubowski, A. Terman, R. Santana, and S. Lee, Passive material properties of stroke-impaired plantarflexor and dorsiflexor muscles, Clin Biomech Bristol Avon, vol.49, pp.48-55, 2017.

E. Ya?ar, E. Adigüzel, and S. Kesikburun, Assessment of forearm muscle spasticity with sonoelastography in patients with stroke, Br J Radiol, vol.89, 1068.

F. Gilbert, D. Klein, and A. M. Weng, Supraspinatus muscle elasticity measured with real time shear wave ultrasound elastography correlates with MRI spectroscopic measured amount of fatty degeneration, BMC Musculoskelet Disord, vol.18, issue.1, p.549, 2017.

C. Tardieu, P. Colbeau-justin, M. D. Bret, A. Lespargot, E. Huet-de-la-tour et al., An apparatus and a method for measuring the relationship of triceps surae torques to tibiotarsal angles in man, Eur J Appl Physiol, vol.35, issue.1, pp.11-20, 1976.

A. Alhusaini, J. Crosbie, R. B. Shepherd, C. M. Dean, and A. Scheinberg, No change in calf muscle passive stiffness after botulinum toxin injection in children with cerebral palsy, Dev Med Child Neurol, vol.53, issue.6, pp.553-558, 2011.

M. Lorenzo, T. Rocon, E. , M. Caballero, I. et al., Prolonged stretching of the ankle plantarflexors elicits muscle-tendon adaptations relevant to ankle gait kinetics in children with spastic cerebral palsy, Med Hypotheses, vol.109, pp.65-69, 2017.

J. Zhou, E. E. Butler, and J. Rose, Neurologic Correlates of Gait Abnormalities in Cerebral Palsy: Implications for Treatment, Front Hum Neurosci, vol.11, p.103, 2017.

J. Gracies, O. Dell, M. Vecchio, and M. , Effects of repeated abobotulinumtoxina injections in upper limb spasticity. Muscle Nerve, 2017.

J. Wissel, D. Bensmail, and J. J. Ferreira, Safety and efficacy of incobotulinumtoxinA doses up to 800 U in limb spasticity: The TOWER study, Neurology, vol.88, issue.14, pp.1321-1328, 2017.

D. Dressler, R. Rychlik, F. Kreimendahl, N. Schnur, and J. Lambert-baumann, Long-term efficacy and safety of incobotulinumtoxinA and conventional treatment of poststroke arm spasticity: a prospective, non-interventional, open-label, parallel-group study, BMJ Open, vol.5, issue.12, p.9358, 2015.

A. Santamato, F. Panza, and D. Intiso, Long-term safety of repeated high doses of incobotulinumtoxinA injections for the treatment of upper and lower limb spasticity after stroke, J Neurol Sci, vol.378, pp.182-186, 2017.

T. Hara, M. Abo, and H. Hara, Effects of botulinum toxin A therapy and multidisciplinary rehabilitation on lower limb spasticity classified by spastic muscle echo intensity in post-stroke patients, Int J Neurosci, pp.1-9, 2017.

A. Picelli, P. Bonetti, and C. Fontana, Is spastic muscle echo intensity related to the response to botulinum toxin type A in patients with stroke? A cohort study, Arch Phys Med Rehabil, vol.93, issue.7, pp.1253-1258, 2012.

J. L. Mcginley, F. Dobson, R. Ganeshalingam, B. J. Shore, E. Rutz et al., Singleevent multilevel surgery for children with cerebral palsy: a systematic review: Review, Dev Med Child Neurol, vol.54, issue.2, pp.117-128, 2012.