Accurate Monitoring of 24-h Real-World Movement Behavior in People with Cerebral Palsy Is Possible Using Multiple Wearable Sensors and Deep Learning.

Monitoring and quantifying movement behavior is crucial for improving the health of individuals with cerebral palsy (CP). We have modeled and trained an image-based Convolutional Neural Network (CNN) to recognize specific movement classifiers relevant to individuals with CP. This study evaluates CNN's performance and determines the feasibility of 24-h recordings. Seven sensors provided accelerometer and gyroscope data from 14 typically developed adults during videotaped physical activity. The performance of the CNN was assessed against test data and human video annotation. For feasibility testing, one typically developed adult and one adult with CP wore sensors for 24 h. The CNN demonstrated exceptional performance against test data, with a mean accuracy of 99.7%. Its general true positives (TP) and true negatives (TN) were 1.00. Against human annotators, performance was high, with mean accuracy at 83.4%, TP 0.84, and TN 0.83. Twenty-four-hour recordings were successful without data loss or adverse events. Participants wore sensors for the full wear time, and the data output were credible. We conclude that monitoring real-world movement behavior in individuals with CP is possible with multiple wearable sensors and CNN. This is of great value for identifying functional decline and informing new interventions, leading to improved outcomes.

Contribution of sensory feedback to soleus muscle activity during voluntary contraction in humans.

Sensory feedback through spinal interneurons contributes to plantar flexor muscle activity during walking, but it is unknown whether this is also the case during nonlocomotor movements. Here, we explored the effect of temporary reduction of sensory feedback to ankle plantar flexors during voluntary contraction in sitting subjects. Thirteen healthy adults (mean age 32 yr) were seated with the right leg attached to a foot plate which could be moved in dorsi- or plantarflexion direction by a computer-controlled motor. EMG was recorded from the tibialis anterior (TA) and soleus (Sol) muscles. During static plantar flexion, while the plantar flexors were slowly stretched, a sudden plantar flexion caused a decline in Sol EMG at the same latency as the stretch reflex. This decline in EMG activity was still observed when transmission from dorsiflexors was blocked. It disappeared when transmission from ankle plantar flexors was also blocked. The same quick plantarflexion failed to produce a decline in EMG activity at the latency of the stretch reflex in the absence of slow stretch of the plantar flexors. Instead, a decline in EMG activity was observed 15-20 ms later. This decline disappeared following block of transmission from antagonists, suggesting that reciprocal inhibition was involved. These findings show that unload of ankle plantar flexors does not cause a similar drop in Sol EMG during voluntary contraction as during walking. This implies that sensory feedback through spinal interneurons only contributes little to the neural drive to plantar flexor muscles during human voluntary contraction in sitting subjects.NEW & NOTEWORTHY Sensory feedback through spinal reflex pathways makes only a minor contribution to neural drive to muscles during voluntary ankle plantar flexion. This differs distinctly from observations during walking and suggests that the neural drive to ankle plantar flexors during voluntary contraction do not rely on sensory feedback through similar spinal interneuronal networks as during walking. In line with animal studies this suggests that the integration of sensory feedback in CNS is task specific.

The effect of cathodal transspinal direct current stimulation on tibialis anterior stretch reflex components in humans.

Spinal DC stimulation (tsDCS) shows promise as a technique for the facilitation of functional recovery of motor function following central nervous system (CNS) lesion. However, the network mechanisms that are responsible for the effects of tsDCS are still uncertain. Here, in a series of experiments, we tested the hypothesis that tsDCS increases the excitability of the long-latency stretch reflex, leading to increased excitability of corticospinal neurons in the primary motor cortex. Experiments were performed in 33 adult human subjects (mean age 28 ± 7 years/14 females). Subjects were seated in a reclining armchair with the right leg attached to a footplate, which could be quickly plantarflexed (100 deg/s; 6 deg amplitude) to induce stretch reflexes in the tibialis anterior (TA) muscle at short (45 ms) and longer latencies (90-95 ms). This setup also enabled measuring motor evoked potentials (MEPs) and cervicomedullary evoked potentials (cMEPs) from TA evoked by transcranial magnetic stimulation (TMS) and electrical stimulation at the cervical junction, respectively. Cathodal tsDCS at 2.5 and 4 mA was found to increase the long-latency reflex without any significant effect on the short-latency reflex. Furthermore, TA MEPs, but not cMEPs, were increased following tsDCS. We conclude that cathodal tsDCS over lumbar segments may facilitate proprioceptive transcortical reflexes in the TA muscle, and we suggest that the most likely explanation of this facilitation is an effect on ascending fibers in the dorsal columns.

Corticomuscular coherence is reduced in relation to dorsiflexion fatigability to the same extent in adults with cerebral palsy as in neurologically intact adults.

PURPOSE: Fatigue is frequent in adults with cerebral palsy (CP) and it is unclear whether this is due to altered corticospinal drive. We aimed to compare changes in corticospinal drive following sustained muscle contractions in adults with CP and neurologically intact (NI) adults. METHODS: Fourteen adults with CP [age 37.6 (10.1), seven females, GMFCS levels I-II] and ten NI adults [age 35.4 (10.3), 6 females] performed 1-min static dorsiflexion at 30% of maximal voluntary contraction (MVC) before and after a submaximal contraction at 60% MVC. Electroencephalography (EEG) and electromyography (EMG) from the anterior tibial muscle were analyzed to quantify the coupling, expressed by corticomuscular coherence (CMC). RESULTS: Adults with CP had lower MVCs but similar time to exhaustion during the relative load of the fatigability trial. Both groups exhibited fatigability-related changes in EMG median frequency and EMG amplitude. The CP group showed lower beta band (16-35 Hz) CMC before fatigability, but both groups decreased beta band CMC following fatigability. There was a linear correlation between decrease of beta band CMC and fatigability-related increase in EMG. CONCLUSION: Fatigability following static contraction until failure was related to decreased beta band CMC in both NI adults and adults with CP. Our findings indicate that compensatory mechanisms to fatigability are present in both groups, and that fatigability affects the corticospinal drive in the same way. We suggest that the perceived physical fatigue in CP is related to the high relative load of activities of daily living rather than any particular physiological mechanism.

Using both electromyography and movement disorder assessment improved the classification of children with dyskinetic cerebral palsy.

AIM: Children with dyskinetic cerebral palsy (CP) are often severely affected and effective treatment is difficult, due to different underlying disease mechanisms. Comprehensive systematic movement disorder evaluations were carried out on patients with this disorder. METHODS: Patients born from 1995 to 2007 were identified from the Danish Cerebral Palsy Register and referrals to the neuropaediatric centre, Rigshospitalet, Copenhagen. They were classified by gross motor function, manual functional ability, communication ability, dystonia and spasticity. Electromyography was carried out on the upper and lower limbs. Magnetic resonance imaging scans were revised, and aetiological searches for underlying genetic disorders were performed. RESULTS: We investigated 25 patients with dyskinetic CP at a mean age of 11.7 years. Dystonia, spasticity and rigidity were found in the upper limbs of 21, four and six children, respectively, and in the lower limbs of 18, 18 and three children. The mean total Burke-Fahn-Marsden score for dystonia was 45.02, and the mean Disability Impairment Scale level was 38% for dystonia and 13% for choreoathetosis. Sustained electromyography activity was observed in 20/25 children. Stretching increased electromyography activity more in children with spasticity. There were 10 re-classifications. CONCLUSION: The children had heterogenic characteristics, and 40% were reclassified after systematic movement disorder evaluation.

Bilateral and asymmetrical contributions of passive and active ankle plantar flexors stiffness to spasticity in humans with spinal cord injury.

Spasticity is one of the most common symptoms present in humans with spinal cord injury (SCI); however, its clinical assessment remains underdeveloped. The purpose of the study was to examine the contribution of passive muscle stiffness and active spinal reflex mechanisms to clinical outcomes of spasticity after SCI. It is important that passive and active contributions to increased muscle stiffness are distinguished to make appropriate decisions about antispastic treatments and to monitor its effectiveness. To address this question, we combined biomechanical and electrophysiological assessments of ankle plantarflexor muscles bilaterally in individuals with and without chronic SCI. Spasticity was assessed using the Modified Ashworth Scale (MAS) and a self-reported questionnaire. We performed slow and fast dorsiflexion stretches of the ankle joint to measure passive muscle stiffness and reflex-induced torque using a dynamometer and the soleus H reflex using electrical stimulation over the posterior tibial nerve. All SCI participants reported the presence of spasticity. While 96% of them reported higher spasticity on one side compared with the other, the MAS detected differences across sides in only 25% of the them. Passive muscle stiffness and the reflex-induced torque were larger in SCI compared with controls more on one side compared with the other. The soleus stretch reflex, but not the H reflex, was larger in SCI compared with controls and showed differences across sides, with a larger reflex in the side showing a higher reflex-induced torque. MAS scores were not correlated with biomechanical and electrophysiological outcomes. These findings provide evidence for bilateral and asymmetric contributions of passive and active ankle plantar flexors stiffness to spasticity in humans with chronic SCI and highlight a poor agreement between a self-reported questionnaire and the MAS for detecting asymmetries in spasticity across sides.NEW & NOTEWORTHY Spasticity affects a number of people with spinal cord injury (SCI). Using biomechanical, electrophysiological, and clinical assessments, we found that passive muscle properties and active spinal reflex mechanisms contribute bilaterally and asymmetrically to spasticity in ankle plantarflexor muscles in humans with chronic SCI. A self-reported questionnaire had poor agreement with the Modified Ashworth Scale in detecting asymmetries in spasticity. The nature of these changes might contribute to the poor sensitivity of clinical exams.

Spastic movement disorder: should we forget hyperexcitable stretch reflexes and start talking about inappropriate prediction of sensory consequences of movement?

Spastic movement disorder is characterized by reduced ability to selectively activate muscles with significant co-activation of antagonist muscles. It has traditionally been thought that hyperexcitable stretch reflexes have a central role in the pathophysiology and the clinical manifestations of the disorder. Here we argue that the main functional challenges for persons with spastic movement disorder are related to contractures, paresis, weak muscles and inappropriate central motor commands, whereas hyperexcitable reflexes play no or only an insignificant functional role. Co-activation of antagonist muscles and stiff posture and gait may rather be adaptations that aim to ensure joint and postural stability due to insufficient muscle strength. Aberrant (involuntary) muscle activity is likely related to an inadequate prediction of the sensory consequences of movement and a resulting impairment of muscle coordination. We argue that improvement of functional muscle strength and muscle coordination following central motor lesions may be achieved by optimizing integration of somatosensory information into central feedforward motor programs, whereas anti-spastic therapy that aims to reduce reflex activity may be less efficient. This opens for novel investigations into new treatment strategies that may improve functional control of movement and prevent reduced joint mobility in people with brain lesions.

Maturation of feedforward toe walking motor program is impaired in children with cerebral palsy.

Voluntary toe walking in adults is characterized by feedforward control of ankle muscles in order to ensure optimal stability of the ankle joint at ground impact. Toe walking is frequently observed in children with cerebral palsy, but the mechanisms involved have not been clarified. Here, we investigated maturation of voluntary toe walking in typically-developing children and typically-developed adults and compared it to involuntary toe walking in children with cerebral palsy. Twenty-eight children with cerebral palsy (age 3-14 years), 24 typically-developing children (age 2-14 years) and 15 adults (mean age 30.7 years) participated in the study. EMG activity was measured from the tibialis anterior and soleus muscles together with knee and ankle joint position during treadmill walking. In typically-developed adults, low step-to-step variability of the drop of the heel after ground impact was correlated with low tibialis anterior and high soleus EMG with no significant coupling between the antagonist muscle EMGs. Typically-developing children showed a significant age-related decline in EMG amplitude reaching an adult level at 10-12 years of age. The youngest typically-developing children showed a broad peak EMG-EMG synchronization (>100 ms) associated with large 5-15 Hz coherence between antagonist muscle activities. EMG coherence declined with age and at the age of 10-12 years no correlation was observed similar to adults. This reduction in coherence was closely related to improved step-to-step stability of the ankle joint position. Children with cerebral palsy generally showed lower EMG levels than typically-developing children and larger step-to-step variability in ankle joint position. In contrast to typically-developing children, children with cerebral palsy showed no age-related decline in tibialis anterior EMG amplitude. Motor unit synchronization and 5-15 Hz coherence between antagonist EMGs was observed more frequently in children with cerebral palsy when compared to typically-developing children and in contrast to typically-developing participants there was no age-related decline. We conclude that typically-developing children develop mature feedforward control of ankle muscle activity as they age, such that at age 10-12 years there is little agonist-antagonist muscle co-contraction around the time of foot-ground contact during toe walking. Children with cerebral palsy, in contrast, continue to co-contract agonist and antagonist ankle muscles when toe walking. We speculate that children with cerebral palsy maintain a co-contraction activation pattern when toe walking due to weak muscles and insufficient motor and sensory signalling necessary for optimization of feedforward motor programs. These findings are important for understanding of the pathophysiology and treatment of toe walking.

Wearable electromyography recordings during daily life activities in children with cerebral palsy.

AIM: To test whether wearable textile electromyography (EMG) recording systems may detect differences in muscle activity levels during daily activities between children with cerebral palsy (CP) and age-matched typically developing children. METHOD: Wearable textile EMG recording systems were used to obtain leg muscle activity in 10 children with spastic CP (four females, six males; mean age 9y 6mo, standard deviation [SD] 2y 4mo, range: 6-13y; Gross Motor Function Classification System [GMFCS] level I and II) and 11 typically developing children (four females, seven males; mean age 9y 9mo, SD 1y 11mo, 7-12y) at rest and while performing seven daily activities. RESULTS: Children with CP showed significantly lower absolute EMG levels during maximal voluntary contractions (MVCs) of muscles on the most affected side as compared to the least affected side and to typically developing children. None of the typically developing children or children with CP showed detectable EMG activity in resting situations. EMG activity relative to MVC was greater in children with CP during walking, jumping, and kicking on the most affected side as compared to the least affected side and to typically developing children. INTERPRETATION: Wearable textile EMG recording systems may be used to determine differences in muscle activity during daily activities in children with CP. Children with CP showed reduced muscle activity during daily activities compared to their peers, but used a significantly larger part of their maximal voluntary muscle strength to perform these activities. WHAT THIS PAPER ADDS: Wearable textile electromyography (EMG) systems are feasible for measurement of daily muscle activity in children with cerebral palsy (CP). Children with CP showed reduced EMG levels during maximal voluntary contractions. Neither typically developing children or children with CP showed EMG activity in resting situations. Children with CP used a larger part of their voluntary muscle strength during daily activities.

Grabaciones de electromiografía portátil durante las actividades de la vida diaria en niños con parálisis cerebral OBJETIVO: Probar si los sistemas de registro de electromiografía textil portátil (EMG) pueden detectar diferencias en los niveles de actividad muscular durante las actividades diarias entre los niños con parálisis cerebral (PC) y los niños de desarrollo típico de la misma edad. MÉTODO: Se utilizaron sistemas de registro de EMG textiles portátiles para obtener actividad muscular de las piernas en 10 niños con PC espástica (cuatro mujeres, seis varones; edad media 9 años y 6 meses, desviación estándar [ED] 2 años y 4 meses, rango: 6-13 años; Escala de clasificación de función motora gruesa [GMFCS] nivel I y II) y 11 niños típicamente en desarrollo (cuatro mujeres, siete varones; edad media 9 años y 9 meses, DE 1 años y 11 meses, 7-12 años) en reposo y mientras realizan siete actividades diarias. RESULTADOS: Los niños con PC mostraron niveles de EMG absolutos significativamente más bajos durante las contracciones voluntarias máximas (CVM) de los músculos en el lado más afectado en comparación con el lado menos afectado y en los niños con desarrollo típico. Ninguno de los niños con desarrollo típico o niños con PC mostró actividad EMG detectable en situaciones de reposo. La actividad EMG en relación con CVM fue mayor en niños con PC al caminar, saltar y patear en el lado más afectado en comparación con el lado menos afectado y en los niños con desarrollo típico. INTERPRETACIÓN: Los sistemas de registro de EMG textiles portátiles pueden usarse para determinar las diferencias en la actividad muscular durante las actividades diarias en niños con PC. Los niños con PC mostraron una actividad muscular reducida durante las actividades diarias en comparación con sus compañeros, pero utilizaron una parte significativamente mayor de su fuerza muscular voluntaria máxima para realizar estas actividades.

Registros vestíveis de eletromiografia durante atividades de vida diária em crianças com paralisia cerebral OBJETIVO: Testar se registros têxteis vestíveis de eletromiografia (EMG) podem detector diferenças nos níveis de atividade muscular durante atividades de vida diária entre crianças com paralisia cerebral (PC) e crianças com desenvolvimento típico da mesma idade. MÉTODO: Sistemas têxteis vestíveis de EMG foram usados para obter a atividade muscular em 10 crianças com PC espástica (quatro do sexo feminino, seis do sexo masculino; média de idade 9a6m, desvio padrão [DP] 2a 4m, variação: 6-13a; Sistema de Classificação da Função Motora Grossa [GMFCS] nível I e II) e 11 crianças com desenvolvimento típico (quatro do sexo feminino, sete do sexo masculino; média de idade 9a 9m, DP 1a 11m, 7-12a) em repouso e durante a realização de sete atividades de vida diária. RESULTADOS: Crianças com PC mostraram níveis de EMG significativamente menores durante contrações voluntárias máximas (CVMs) de músculos no lado mais afetado, em comparação com o lado menos afetado e com crianças típicas. Nenhuma das crianças típicas ou com PC mostrou atividade de EMG detectável nas situações de repouso. A atividade de EMG relativa a CVM foi maior em crianças com PC durante a marcha, salto e chutes no lado mais afetado em comparação com o lado menos afetado e com crianças típicas. INTERPRETAÇÃO: Sistemas têxteis vestíveis para registro de EMG podem ser usados para determinar diferenças na atividade muscular durante atividades de vida diária em crianças com PC. Crianças com PC mostraram reduzida atividade muscular durante atividades diárias comparadas com seus pares, mas usaram uma porção significativamente maior de sua força voluntária máxima para realizar estas atividades.

Contribution of corticospinal drive to ankle plantar flexor muscle activation during gait in adults with cerebral palsy.

Impaired plantar flexor muscle activation during push-off in late stance contributes importantly to reduced gait ability in adults with cerebral palsy (CP). Here we used low-intensity transcranial magnetic stimulation (TMS) to suppress soleus EMG activity during push-off as an estimate of corticospinal drive in CP adults and neurologically intact (NI) adults. Ten CP adults (age 34 years, SD 14.6, GMFCS I-II) and ten NI adults (age 33 years, SD 9.8) walked on a treadmill at their preferred walking speed. TMS of the leg motor cortex was elicited just prior to push-off during gait at intensities below threshold for motor-evoked potentials. Soleus EMG from steps with and without TMS were averaged and compared. Control experiments were performed while standing and in NI adults during gait at slow speed. TMS induced a suppression at a latency of about 40 ms. This suppression was similar in the two populations when differences in control EMG and gait speed were taken into account (CP 18%, NI 16%). The threshold of the suppression was higher in CP adults. The findings suggest that corticospinal drive to ankle plantar flexors at push-off is comparable in CP and NI adults. The higher threshold of the suppression in CP adults may reflect downregulation of cortical inhibition to facilitate corticospinal drive. Interventions aiming to facilitate excitability in cortical networks may contribute to maintain or even improve efficient gait in CP adults.

Characterization of torque generating properties of ankle plantar flexor muscles in ambulant adults with cerebral palsy.

PURPOSE: Weakness of plantar flexor muscles is related to reduced push-off and forward propulsion during gait in persons with cerebral palsy (CP). It has not been clarified to what an extent altered muscle contractile properties contribute to this muscle weakness. Here, we investigated the torque generating capacity and muscle fascicle length in the triceps surae muscle throughout ankle range of motion (ROM) in adults with CP using maximal single muscle twitches elicited by electrical nerve stimulation and ultrasonography. METHODS: Fourteen adults with CP (age 36, SD 10.6, GMFCS I-III) and 17 neurological intact (NI) adults (age 36, SD 4.5) participated. Plantar flexor torque during supramaximal stimulation of the tibial nerve was recorded in a dynamometer at 8 ankle angles throughout ROM. Medial gastrocnemius (MG) fascicle length was tracked using ultrasonography. RESULTS: Adults with CP showed reduced plantar flexor torque and fascicle shortening during supramaximal stimulation throughout ROM. The largest torque generation was observed at the ankle joint position where the largest shortening of MG fascicles was observed in both groups. This was at a more plantarflexed position in the CP group. CONCLUSION: Reduced torque and fascicle shortening during supramaximal stimulation of the tibial nerve indicate impaired contractile properties of plantar flexor muscles in adults with CP. Maximal torque was observed at a more plantarflexed position in adults with CP indicating an altered torque-fascicle length/ankle angle relation. The findings suggest that gait rehabilitation in adults with CP may require special focus on improvement of muscle contractility.

Children with dyskinetic cerebral palsy are severely affected as compared to bilateral spastic cerebral palsy.

AIM: We aimed at describing clinical findings in children with dyskinetic as compared to bilateral spastic cerebral palsy (CP). METHODS: Data were extracted from the Danish nationwide CP register. Participants were born in 1999-2007 and were 5-6 years at ascertainment. RESULTS: The total number of CP cases was 1165 of which 92 had dyskinetic and 540 bilateral spastic CP. Prevalence of dyskinetic CP was 0.16 per 1000 live births. In participants with dyskinetic compared to bilateral spastic CP, there was more frequently an Apgar level less than five at five minutes (22.7% vs. 11.2%) and neonatal seizures (43.5% vs. 28.5%), but less respiratory deficiency, hyperbilirubinaemia and sepsis. Impairment based on gross motor function classification was more severe in dyskinetic CP (level III-V 90.0% vs. 66.0%). In dyskinetic CP, there was a high rate of reduced developmental quotient (68.1%), visual impairment (39.3%) and epilepsy (51.6%). Basal ganglia lesions were more prevalent in dyskinetic compared to bilateral spastic CP (27.7% vs. 12.8%). CONCLUSION: Cases of dyskinetic CP had overlapping clinical features with cases of bilateral spastic CP, but differed significantly in several perinatal risk factors. The children with dyskinetic CP had experienced more peri- or neonatal adverse events, and neurodevelopmental impairment was severe.

Effects on Parental Stress of Early Home-Based CareToy Intervention in Low-Risk Preterm Infants.

Parenting a preterm infant is more challenging than a full-term one. Parent involvement in early intervention programs seems to have positive psychosocial effects on both the child and parent. CareToy is an innovative smart system that provides an intensive individualized home-based family-centred EI in preterm infants between 3 and 9 age-corrected months. A RCT study, preceded by a pilot study, has been recently carried out to evaluate the effects of CareToy intervention on neurodevelopmental outcomes with respect to Standard Care. This study aims at evaluating the effects of CareToy early intervention on parenting stress in preterm infants. Parents (mother and father) of a subgroup of infants enrolled in the RCT filled out a self-report questionnaire on parenting stress (Parenting Stress Index-Short Form (PSI-SF)) before (T0) and after (T1) the CareToy or Standard Care period (4 weeks), according to the allocation of their preterm infant. For twins, an individual questionnaire for each one was filled out. Results obtained from mothers and fathers were separately analysed with nonparametric tests. 44 mothers and 44 fathers of 44 infants (24 CareToy/20 Standard Care) filled out the PSI-SF at T0 and at T1. CareToy intervention was mainly managed by mothers. A significant (p < 0.05) reduction in Parental Distress subscale in the CareToy group versus Standard Care was found in the mothers. No differences were found among the fathers. CareToy training seems to be effective in reducing parental distress in mothers, who spent more time on CareToy intervention. These findings confirm the importance of parental involvement in early intervention programs. This trial is registered with Clinical Trial.gov NCT01990183.

Sequence variants in muscle tissue-related genes may determine the severity of muscle contractures in cerebral palsy.

Muscle contractures are a common complication to cerebral palsy (CP). The purpose of this study was to evaluate whether individuals with CP carry specific gene variants of important structural genes that might explain the severity of muscle contractures. Next-generation-sequencing (NGS) of 96 candidate genes associated with muscle structure and metabolism were analyzed in 43 individuals with CP (Gross Motor Function classification system [GMFCS] I, n=10; GMFCS II, n=14; GMFCS III, n=19) and four control participants. In silico analysis of the identified variants was performed. The variants were classified into four categories ranging from likely benign (VUS0) to highly likely functional effect (VUS3). All individuals with CP were classified and grouped according to their GMFCS level: Statistical comparisons were made between GMFCS groups. Kruskal-Wallis tests showed significantly more VUS2 variants in the genes COL4 (GMFCS I-III; 1, 1, 5, respectively [p < .04]), COL5 (GMFCS I-III; 1, 1, 5 [p < .04]), COL6 (GMFCS I-III; 0, 4, 7 [p < .003]), and COL9 (GMFCS I-III; 1, 1, 5 [p < .04]), in individuals with CP within GMFCS Level III when compared to the other GMFCS levels. Furthermore, significantly more VUS3 variants in COL6 (GMFCS I-III; 0, 5, 2 [p < .01]) and COL7 (GMFCS I-III; 0, 3, 0 [p < .04]) were identified in the GMFCS II level when compared to the other GMFCS levels. The present results highlight several candidate gene variants in different collagen types with likely functional effects in individuals with CP.

Feedforward neural control of toe walking in humans.

KEY POINTS: Activation of ankle muscles at ground contact during toe walking is unaltered when sensory feedback is blocked or the ground is suddenly dropped. Responses in the soleus muscle to transcranial magnetic stimulation, but not peripheral nerve stimulation, are facilitated at ground contact during toe walking. We argue that toe walking is supported by feedforward control at ground contact. ABSTRACT: Toe walking requires careful control of the ankle muscles in order to absorb the impact of ground contact and maintain a stable position of the joint. The present study aimed to clarify the peripheral and central neural mechanisms involved. Fifteen healthy adults walked on a treadmill (3.0 km h-1 ). Tibialis anterior (TA) and soleus (Sol) EMG, knee and ankle joint angles, and gastrocnemius-soleus muscle fascicle lengths were recorded. Peripheral and central contributions to the EMG activity were assessed by afferent blockade, H-reflex testing, transcranial magnetic brain stimulation (TMS) and sudden unloading of the planter flexor muscle-tendon complex. Sol EMG activity started prior to ground contact and remained high throughout stance. TA EMG activity, which is normally seen around ground contact during heel strike walking, was absent. Although stretch of the Achilles tendon-muscle complex was observed after ground contact, this was not associated with lengthening of the ankle plantar flexor muscle fascicles. Sol EMG around ground contact was not affected by ischaemic blockade of large-diameter sensory afferents, or the sudden removal of ground support shortly after toe contact. Soleus motor-evoked potentials elicited by TMS were facilitated immediately after ground contact, whereas Sol H-reflexes were not. These findings indicate that at the crucial time of ankle stabilization following ground contact, toe walking is governed by centrally mediated motor drive rather than sensory driven reflex mechanisms. These findings have implications for our understanding of the control of human gait during voluntary toe walking.

Impaired muscle growth precedes development of increased stiffness of the triceps surae musculotendinous unit in children with cerebral palsy.

AIM: If increased muscle stiffness and contractures in children with cerebral palsy (CP) are related to impaired muscle growth, reduced muscle growth should precede or coincide with increased muscle stiffness during development. Here, we compared the volume of the medial gastrocnemius muscle and the passive (non-neural) stiffness of the triceps surae musculotendinous unit in typically developing children and children with CP from birth until 4 years of age. METHOD: Forty-one children with CP and 45 typically developing children were included. Freehand three-dimensional ultrasound was used to evaluate the volume of the medial gastrocnemius muscle. Biomechanical and electrophysiological measures were used to determine passive and reflex mediated stiffness of the triceps surae musculotendinous unit. RESULTS: Medial gastrocnemius muscle volume increased with the same rate in typically developing and children with CP until 12 months of age, when a significant smaller rate of growth was observed in children with CP. Passive stiffness of the triceps surae musculotendinous unit showed a linear increase with age in typically developing children. Children with CP older than 27 months showed a significant increase in passive stiffness. Reflex mediated stiffness was only pathologically increased in four children with CP. INTERPRETATION: The deviation of medial gastrocnemius muscle volume, earlier than musculotendinous unit stiffness, is consistent with the hypothesis. The data also point out that muscle atrophy and muscle stiffness already develops within the first 1 to 2 years. This emphasizes the necessity of early interventions to promote lower limb muscle growth in this population. WHAT THIS PAPER ADDS: Medial gastrocnemius muscle growth is reduced in children with cerebral palsy (CP) around 12 months after birth. Triceps surae musculotendinous unit stiffness is increased in children with CP around 27 months after birth. Reflex excitability is rarely increased in children with CP. Reduced muscle growth may be involved in the pathophysiology of contractures.

Development and aging of human spinal cord circuitries.

The neural motor circuitries in the spinal cord receive information from our senses and the rest of the nervous system and translate it into purposeful movements, which allow us to interact with the rest of the world. In this review, we discuss how these circuitries are established during early development and the extent to which they are shaped according to the demands of the body that they control and the environment with which the body has to interact. We also discuss how aging processes and physiological changes in our body are reflected in adaptations of activity in the spinal cord motor circuitries. The complex, multifaceted connectivity of the spinal cord motor circuitries allows them to generate vastly different movements and to adapt their activity to meet new challenges imposed by bodily changes or a changing environment. There are thus plenty of possibilities for adaptive changes in the spinal motor circuitries both early and late in life.

Contribution of sensory feedback to plantar flexor muscle activation during push-off in adults with cerebral palsy.

Exaggerated sensory activity has been assumed to contribute to functional impairment following lesion of the central motor pathway. However, recent studies have suggested that sensory contribution to muscle activity during gait is reduced in stroke patients and children with cerebral palsy (CP). We investigated whether this also occurs in CP adults and whether daily treadmill training is accompanied by alterations in sensory contribution to muscle activity. Seventeen adults with CP and 12 uninjured individuals participated. The participants walked on a treadmill while a robotized ankle-foot orthosis applied unload perturbations at the ankle, thereby removing sensory feedback naturally activated during push-off. Reduction of electromyographic (EMG) activity in the soleus muscle caused by unloads was compared and related to kinematics and ankle joint stiffness measurements. Similar measures were obtained after 6 wk of gait training. We found that sensory contribution to soleus EMG activation was reduced in CP adults compared with uninjured adults. The lowest contribution of sensory feedback was found in participants with lowest maximal gait speed. This was related to increased ankle plantar flexor stiffness. Six weeks of gait training did not alter the contribution of sensory feedback. We conclude that exaggerated sensory activity is unlikely to contribute to impaired gait in CP adults, because sensory contribution to muscle activity during gait was reduced compared with in uninjured individuals. Increased passive stiffness around the ankle joint is likely to diminish sensory feedback during gait so that a larger part of plantar flexor muscle activity must be generated by descending motor commands.NEW & NOTEWORTHY Findings suggest that adults with cerebral palsy have less contribution of sensory feedback to ongoing soleus muscle activation during push-off than uninjured individuals. Increased passive stiffness around the ankle joint is likely to diminish sensory feedback during gait, and/or sensory feedback is less integrated with central motor commands in the activation of spinal motor neurons. Consequently, muscle activation must to a larger extent rely on descending drive, which is already decreased because of the cerebral lesion.

To be active through indoor-climbing: an exploratory feasibility study in a group of children with cerebral palsy and typically developing children.

BACKGROUND: Cerebral Palsy (CP) is the most common cause of motor disabilities in children and young adults and it is also often associated with cognitive and physiological challenges. Climbing requires a multifaceted repertoire of movements, participants at all levels of expertise may be challenged functionally and cognitively, making climbing of great potential interest in (re)habilitation settings. However, until now only few research projects have investigated the feasibility of climbing as a potential activity for heightening physical activity in children with CP and the possible beneficial effects of climbing activities in populations with functional and/or cognitive challenges. The aim of this study was therefore to test the feasibility of an intensive 3 weeks indoor-climbing training program in children with CP and typically developing (TD) peers. In addition we evaluated possible functional and cognitive benefits of 3 weeks of intensive climbing training in 11 children with cerebral palsy (CP) aged 11-13 years and six of their TD peers. METHOD: The study was designed as a feasibility and interventional study. We evaluated the amount of time spent being physically active during the 9 indoor-climbing training sessions, and climbing abilities were measured. The participants were tested in a series of physiological, psychological and cognitive tests: two times prior to and one time following the training in order to explore possible effects of the intervention. RESULTS: The children accomplished the training goal of a total of nine sessions within the 3-week training period. The time of physical activity during a 2:30 h climbing session, was comparably high in the group of children with CP and the TD children. The children with CP were physically active on average for almost 16 h in total during the 3 weeks. Both groups of participants improved their climbing abilities, the children with CP managed to climb a larger proportion of the tested climbing route at the end of training and the TD group climbed faster. For the children with CP this was accompanied by significant improvements in the Sit-to-stand test (p < 0.01), increased rate of force development in the least affected hand during an explosive pinch test and increased muscular-muscular coherence during a pinch precision test (p < 0.05). We found no improvements in maximal hand or finger strength and no changes in cognitive abilities or psychological well-being in any of the groups. CONCLUSIONS: These findings show that it is possible to use climbing as means to make children with CP physically active. The improved motor abilities obtained through the training is likely reflected by increased synchronization between cortex and muscles, which results in a more efficient motor unit recruitment that may be transferred to daily functional abilities. TRIAL REGISTRATION: ISRCTN18006574; day of registration: 09/05/2017; the trial is registered retrospectively.

Botulinum toxin injection causes hyper-reflexia and increased muscle stiffness of the triceps surae muscle in the rat.

Botulinum toxin is used with the intention of diminishing spasticity and reducing the risk of development of contractures. Here, we investigated changes in muscle stiffness caused by reflex activity or elastic muscle properties following botulinum toxin injection in the triceps surae muscle in rats. Forty-four rats received injection of botulinum toxin in the left triceps surae muscle. Control measurements were performed on the noninjected contralateral side in all rats. Acute experiments were performed, 1, 2, 4, and 8 wk following injection. The triceps surae muscle was dissected free, and the Achilles tendon was cut and attached to a muscle puller. The resistance of the muscle to stretches of different amplitudes and velocities was systematically investigated. Reflex-mediated torque was normalized to the maximal muscle force evoked by supramaximal stimulation of the tibial nerve. Botulinum toxin injection caused severe atrophy of the triceps surae muscle at all time points. The force generated by stretch reflex activity was also strongly diminished but not to the same extent as the maximal muscle force at 2 and 4 wk, signifying a relative reflex hyperexcitability. Passive muscle stiffness was unaltered at 1 wk but increased at 2, 4, and 8 wk (P < 0.01). These data demonstrate that botulinum toxin causes a relative increase in reflex stiffness, which is likely caused by compensatory neuroplastic changes. The stiffness of elastic elements in the muscles also increased. The data are not consistent with the ideas that botulinum toxin is an efficient antispastic medication or that it may prevent development of contractures.