Development of postural adjustments during reaching in typically developing infants from 4 to 18 months

The relationship between segmental trunk control and gross motor performance in low birth weight born infants

OBJECTIVE

Trunk control is associated with gross motor development. This study examines the relationship between segmental trunk control and gross motor performance in low birth weight (LBW) infants.

METHODS

A total of 42 LBW infants and 43 normal birth weight (NBW) infants aged 3-9 months were sampled for this cross-sectional study. All infants were evaluated one time by the Segmental Assessment Trunk Control (SATCo) and the Alberta Infant Motor Scale (AIMS).

RESULTS

Statistically high and significant correlations were found between gross motor performance and segmental trunk control in all sample populations (r = 0.835; p = .001). No statistically significant difference was found regarding the segmental trunk control between the groups (p = .119). The LBW infants with atypical motor development had poorer trunk control than the LBW infants with typical development (f = 5.480; p = .001).

CONCLUSION

Our results show that LBW infants with atypical motor development had poorer trunk control than LBW infants with typical motor development. It was found that the segmental trunk controls of LBW infants were 0.398 times lower than in NBW infants.

Correlations between Trunk Control and Balance in Children with Bilateral Spastic Cerebral Palsy

Impairments of postural responses are a salient feature of children with cerebral palsy (CP). While the systems approach describes balance in seven components, the relationship between trunk control and balance in children with CP has not been previously examined with all seven of these components. In this study, we aimed to identify correlations between trunk control and all seven systems approach balance components in children with bilateral spastic CP. Our participants were 30 children (M age = 11.83, SD = 2.32 years) with CP having a Gross Motor Function Classification System level ranging from I to III. We assessed trunk control with the Trunk Control Measurement Scale, including static and dynamic balance (selective voluntary control and reaching). Balance in standing was assessed using Kids-Mini-BESTest involving four domains: anticipatory, reactive, sensory orientation and stability in gait. We used Spearman's rank correlations to correlate trunk control and balance, and we obtained a moderate correlation between the trunk control measurement scale and the Kids-Mini-BESTest in children with both bilateral spastic CP (rs = .618, p < .001) and spastic diplegic CP (rs = .52, p = .02). Analysis of the correlations between separate domains of the Kids-Mini-BESTest and the trunk control measurement scale subscales revealed moderate correlations between the static sitting balance subscale and all four domains of the Kids-Mini-BESTest. The dynamic selective motor control subscale of the trunk control measurement scale moderately correlated with the anticipatory domain of the Kids-Mini-BESTest. The dynamic reaching subscale also correlated moderately with anticipatory and stability in gait domains. This correlation was statistically significant in the 13 to 17-year-old age group and was strong among females, whereas the correlation was moderate in males. Trunk control was moderately associated with balance considering all the systems theory components of balance in children with bilateral spastic cerebral palsy.

In Context: A Developmental Model of Reward Processing, With Implications for Autism and Sensitive Periods

OBJECTIVE

Differences in reward processing have been associated with numerous psychiatric disorders, including autism and attention-deficit/hyperactivity disorder (ADHD). Many attempts to understand reward processing characterize differences in clinical populations after disorder onset; however, divergence may begin much earlier. In fact, the typical developmental progression of reward processing in infancy and early childhood is poorly understood. We re-conceptualize classic infant developmental constructs such as preferential looking into a Six-Component Developmental Model of Reward Processing: an infant- and young child-focused framework to guide research and assessment of reward processing across development.

METHOD

The extant developmental literature including recent textbooks, systematic reviews, and meta-analyses was reviewed to build a conceptual framework. We describe experimental paradigms to assess each developmental component of reward processing longitudinally from infancy. A timeline of each component's emergence was estimated.

RESULTS

Six components of reward processing were identified-association, discrimination, preference/valuation, effort, anticipation, and response. Selected evidence suggests emergence between birth and 6 months. Application of this model to autism led to a reinterpretation of existing disparate results, and illuminated a path to study the developmental processes underlying a popular hypothesis of autism, the motivation hypothesis. Current evidence further suggests that a sensitive period may exist for the emergence of reward processing.

CONCLUSION

The proposed framework offers a useful reconceptualization of the extant literature. Future longitudinal work using the suggested experimental paradigms with high-risk populations could elucidate the developmental trajectory of the components and timing of potential sensitive period(s) for each component.

Biological and environmental factors may affect children's executive function through motor and sensorimotor development: Preterm birth and cerebral palsy

Disruptive biological and environmental factors may undermine the development of children's motor and sensorimotor skills. Since the development of cognitive skills, including executive function, is grounded in early motor and sensorimotor experiences, early delays or impairments in motor and sensorimotor processing often trigger dynamic developmental cascades that lead to suboptimal executive function outcomes. The purpose of this perspective paper is to link early differences in motor/sensorimotor processing to the development of executive function in children born preterm or with cerebral palsy. Uncovering such links in clinical populations would improve our understanding of developmental pathways and key motor and sensorimotor skills that are antecedent and foundational for the development of executive function. This knowledge will allow the refinement of early interventions targeting motor and sensorimotor skills with the goal of proactively improving executive function outcomes in at-risk populations.

Differences between Novice and Expert Raters Assessing Trunk Control Using the Trunk Control Measurement Scale Spanish Version (TCMS-S) in Children with Cerebral Palsy

The Trunk Control Measurement Scale (TCMS) is a valid and reliable tool to assess static and dynamic trunk control in cerebral palsy. However, there is no evidence informing about differences between novice and expert raters. A cross-sectional study was conducted with participants between the ages of 6 and 18 years with a CP diagnosis. The TCMS Spanish version (TCMS-S) was administered in-person by an expert rater, and video recordings were taken for later scoring by the expert and three other raters with varying levels of clinical experience. The intraclass correlation coefficient (ICC) was used to evaluate reliability between raters for the total and subscales of the TCMS-S scores. Standard Error of Measurement (SEM) and Minimal Detectable Change (MDC) were also calculated. There was a high level of agreement between expert raters (ICC ≥ 0.93), while novice raters demonstrated good agreement (ICC > 0.72). Additionally, it was observed that novice raters had a slightly higher SEM and MDC than expert raters. The Selective Movement Control subscale exhibited slightly higher SEM and MDC values compared to the TCMS-S total and other subscales, irrespective of the rater's level of expertise. Overall, the study showed that the TCMS-S is a reliable tool for evaluating trunk control in the Spanish pediatric population with cerebral palsy, regardless of the rater's experience level.

Trunk Control Measurement Scale (TCMS): Psychometric Properties of Cross-Cultural Adaptation and Validation of the Spanish Version

The aim of this study was to develop a Spanish Version of the Trunk Measurement Scale (TCMS-S) to analyze its validity and reliability and determine the Standard Error of Measurement (SEM) and Minimal Detectable Change (MDC) in children with Cerebral Palsy (CP). Participants were assessed twice 7-15 days apart with the TCMS-S and once with the Gross Motor Function Measurement-88 (GMFM-88), Pediatric Disability Inventory-Computer Adaptive Test (PEDI-CAT), Cerebral Palsy Quality of Life (CPQoL), and Gross Motor Classification System (GMFCS). Internal consistency was evaluated using Cronbach's alpha, and the intraclass correlation (ICC) and kappa coefficients were used to investigate the agreement between the assessments. Finally, 96 participants with CP were included. The TCMS-S showed excellent internal consistency (Cronbach's alpha = 0.95 [0.93 to 0.96]); was highly correlated with the GMFM-88 (rho = 0.816) and the "mobility" subscale of the PEDI-CAT (rho = 0.760); showed a moderate correlation with the "feeling about functioning" CPQoL subscale (rho = 0.576); and differentiated between the GMFCS levels. Excellent test-retest agreement was found for the total and subscale scores (ICC ≥ 0.94 [0.89 to 0.97). For the total TCMS-S score, an SEM of 1.86 and an MDC of 5.15 were found. The TCMS-S is a valid and reliable tool for assessing trunk control in children with CP.

Atypical knee jerk responses in high-risk children: A longitudinal EMG-study

INTRODUCTION

We previously found that atypical responses to the knee jerk reflex, i.e., tonic responses (TRs), clonus and contralateral responses in very high-risk (VHR) infants were associated with cerebral palsy (CP) at 21 months. The current study aimed for a better understanding of pathophysiology of atypical knee jerk responses by evaluating whether infant atypical knee jerk responses are associated with CP and atypical knee jerk responses at school-age.

METHODS

31 VHR-children, who had also been assessed longitudinally during infancy, and 24 typically developing children, were assessed at 7-10 years (school-age). We continuously recorded surface EMG of thigh muscles during knee jerk responses longitudinally during infancy and once at school-age. Neurological condition was assessed with age-appropriate neurological examinations. It included the diagnosis of CP at 21 months corrected age and school-age. CP's type and severity (Gross Motor Function Classification System (GMFCS)) were reported.

RESULTS

Persistent TRs in infancy were associated with CP at school-age. TR prevalence decreased from infancy to childhood. At school-age it was no longer associated with CP. Clonus prevalence in VHR-children did not change with increasing age; it was significantly higher in children without than those with CP. Reflex irradiation was common in all school-age children, and its prevalence in contralateral muscles in VHR-children decreased between infancy and childhood.

CONCLUSIONS

In infancy, TRs indicated an increased risk of CP, but at school-age TRs were not associated with CP. In general, spinal hyperexcitability, expressed as reflex irradiation and TRs, decreased between infancy and school-age.

Recording activity in proximal muscle networks with surface EMG in assessing infant motor development

OBJECTIVE

To develop methods for recording and analysing infant's proximal muscle activations.

METHODS

Surface electromyography (sEMG) of truncal muscles was recorded in three months old infants (N = 18) during spontaneous movement and controlled postural changes. The infants were also divided into two groups according to motor performance. We developed an efficient method for removing dynamic cardiac artefacts to allow i) accurate estimation of individual muscle activations, as well as ii) quantitative characterization of muscle networks.

RESULTS

The automated removal of cardiac artefacts allowed quantitation of truncal muscle activity, which showed predictable effects during postural changes, and there were differences between high and low performing infants.The muscle networks showed consistent change in network density during spontaneous movements between supine and prone position. Moreover, activity correlations in individual pairs of back muscles linked to infant́s motor performance.

CONCLUSIONS

The hereby developed sEMG analysis methodology is feasible and may disclose differences between high and low performing infants. Analysis of the muscle networks may provide novel insight to central control of motility.

SIGNIFICANCE

Quantitative analysis of infant's muscle activity and muscle networks holds promise for an objective neurodevelopmental assessment of motor system.

Does late preterm birth impact trunk control and early reaching behavior?

The aims of the study were to 1) verify the level of trunk control longitudinally and reaching behavior while sitting in two positions in late preterm (LPT) and full-term (FT) infants, 2) determine whether the level of trunk control relates to reaching outcomes. Twenty LPT infants and 36 infants born FT were assessed via three in-lab visits: at 6, 7, and 8 months. At each visit, the Segmental Assessment of Trunk Control (SATCo) and reaching assessment were performed, where the infants were positioned sitting in the ring and at 90° of flexion of hips, knees, and ankles. Accurate manual support to the trunk was provided in each visit. LPT infants presented a lower level of trunk control over time. LPT infants presented a higher percentage of unimanual reaches and successful grasping at 7 months' visit, and a higher number of reaches at 8 months' visit compared to FT infants. The sitting positions did not influence reaching performance. The level of trunk control relates to functional reaching strategies only in FT infants. This study might provide insights for clinicians for understanding the level of trunk control, the importance of reaching behaviors for exploration, and considering these behaviors as strategies for intervention.

Fetal development of the thoracolumbar fascia with special reference to the fascial connection with the transversus abdominis, latissimus dorsi, and serratus posterior inferior muscles

PURPOSE

The three-layered thoracolumbar fascia (TLF) encapsulates the erector spinae and the quadratus lumborum and has been a major concern for physical therapists. However, knowledge of its prenatal development and growth is limited.

METHODS

Histological examination of 25 embryos and fetuses at 6-37 weeks (CRLs, 15-310 mm).

RESULTS

At the posterior end, the abdominal muscles continued toward an initial posterior layer of the TLF (pTLF) at 6 weeks, but the connection became narrow and limited to the obliquus externus aponeurosis until near term. The middle layer of the TLF (mTLF) appeared as a posterior continuation of the transversalis fascia at 9 weeks and, depending on a mechanical demand for the vertebral column extension near term, it grew as a thick intermuscular septum between the iliocostalis and quadratus lumborum. Thus, the mTLF lateral end changed from the abdominal wall to the back or pTLF. The serratus posterior inferior originated from the pTLF after 9 weeks, but a connection of the latissimus dorsi with the fascia was established much later. Near term, the gluteus maximus was attached to an aponeurosis covering the multifidus behind the sacrum. Therefore, the pTLF extended to cover the gluteal muscles.

CONCLUSION

We rejected the hypothesis that the mTLF develops as a marginal tissue between the primitive epaxial and hypaxial muscles. This study seemed to be the first report showing a fact that, within prenatal life, a drastic change is likely to occur in interfascial connections and their topographical relation to muscles; the TLF might be the best sample.

How Has Electromyography Been Used to Assess Reaching in Infants? A Systematic Review

The aims of this systematic review were: to investigate the use of surface electromyography in the assessment of reaching in infants; to assess the usefulness of this tool to the assessment of reaching, and its parameters and limitations; to assess the methodological quality of the studies available in the literature. The search in the databases MEDLINE, SciELO, LILACS, Embase, PEDro, Cochrane, and EBSCO resulted in 5 selected studies. The studies aimed to elucidate how muscle behavior occurs in the development of reaching. The lack of standardized recommendations for the use of EMG in infants limit the reproducibility and comparison between studies. There are challenges and limitations regarding the use of electromyography in infants, which are caused by peculiarities inherent to the development of the neuromotor and musculoskeletal systems.

Electromyographic activity of head and trunk muscles in newborns

Abstract Introduction: The electric activity of muscles can be assessed using electromyography to determine their function and help identify possible delays in motor development. Objective: Determine the amplitude of the electromyographic activity of the head and trunk flexor and extensor muscles of term and preterm newborns. Method: This is a longitudinal pilot study where 20 preterm and 20 term newborns admitted to the Prof. Fernando Figueira Institute of Comprehensive Medicine were assessed. All the newborns were evaluated between 24 and 72 hours after delivery, with the premature children assessed a second time when term equivalent age was reached at 40 weeks. Data were recorded using a surface electromyograph and the electrodes were attached to the muscle bellies of the sternocleidomastoid, upper portion of the trapezius, rectus abdominis and erector spinae muscles. Results: Comparison of the electromyographic activity between the preterm newborns showed significantly higher values in all the muscles when the group reached term equivalent age. Additionally, the electromyographic activity of the term group was greater than that obtained by the preterm newborns. Conclusion: With advancing age and maturation of the physiological systems, including the muscle system, preterm newborns tend to exhibit a similar muscle activation behavior to that of the term infants, resulting in better motor development.

Is Segmental Trunk Control Related to Gross Motor Performance in Healthy Preterm and Full-Term Infants?

The authors' aim was to verify the correlation between segmental trunk control and gross motor performance in healthy preterm (PT) and full-term (FT) infants aged 6 and 7 months and to verify if there are differences between groups. All infants were assessed at 6 and 7 months by means of Segmental Assessment of Trunk Control (SATCo) to identify the exact level of segmental trunk control and Alberta Infant Motor Scale (AIMS) to measure gross motor performance. A significant correlation between segmental trunk control and gross motor performance was found in healthy PT infants at 7 months and FT infants at 6 months. PT infants showed a delay on segmental trunk control at 6 and 7 months and in supported standing posture at 6 months compared with FT infants. Segmental trunk control and gross motor performance showed an important relationship in healthy PT and FT infants, mainly in sitting posture.

Effects of forward tilted seating and foot-support on postural adjustments in children with spastic cerebral palsy: An EMG-study

OBJECTIVE

To evaluate the effect of 15° forward (FW) seat inclination and foot-support in children with cerebral palsy (CP) on postural adjustments during reaching.

DESIGN

Observational study repeated-measures design; step two of two-step-project.

SETTING

Laboratory unit within University Hospital and two special education schools.

PARTICIPANTS

19 children (ten unilateral spastic CP (US-CP); nine bilateral spastic CP (BS-CP); Gross Motor Function Classification System levels I-III; 6-12 years old). Participants were able to take part for one one-hour session.

INTERVENTION

Reaching while sitting in four seating conditions (FW or horizontal seat; with or without foot-support) applied in randomized order.

OUTCOME MEASURES

Simultaneously, surface electromyography (EMG) of neck, trunk and arm muscles and kinematics of head and reaching arm (step one of two-step-project) were recorded. Primary outcome parameters were the ability to modulate EMG-amplitudes at baseline and during reaching (phasic muscle activity). Other EMG-parameters were direction-specificity (1st control level), and 2nd level of control parameters: recruitment order, and anticipatory postural activity. Motor behaviour measures: ability to modulate EMG-amplitudes to kinematic characteristics of reaching and head stability.

RESULTS

Only foot-support was associated with increased tonic background EMG-amplitudes and decreased phasic EMG-amplitudes of the trunk extensors in children with US-CP and BS-CP (mixed-models analyses; p-values <0.01). The foot-support effect was also associated with better kinematics of reaching (Spearman's Rho; p-values <0.01).

CONCLUSION

In terms of postural adjustments during forward reaching, foot-support enhanced the children's capacity to modulate trunk extensor activity, which was associated with improved reaching quality. FW-tilting did not affect postural muscle activity.

Postural control during reaching while sitting and general motor behaviour when learning to walk

AIM

To study changes in muscular postural strategies and general motor behaviour during the transition to independent walking. Postural control was assessed at its two functional levels: (1) direction specificity, in which dorsal muscles are primarily activated when reaching forward; and (2) fine-tuning of direction specificity.

METHOD

In an explorative longitudinal study, surface electromyograms of the arm, trunk, and neck muscles of 28 typically developing infants were recorded during reaching while sitting. Each infant was assessed in three developmental phases: during pull-to-stand (T0), first independent steps (T1), and 1 month after T1 (T2). Motor behaviour was assessed using the Infant Motor Profile (IMP). The effect on developmental outcome measures (postural parameters and IMP) of the developmental phases (T0, T1, T2) was estimated using linear mixed-effects models.

RESULTS

None of the postural parameters changed significantly over time. However, individual developmental trajectories showed infant-specific postural reorganizational changes. Total IMP score decreased between T0 and T1 (mean IMP score 95% and 91% respectively; p<0.001); between T1 and T2 IMP scores did not change (91% and 93%; p=0.073).

INTERPRETATION

Typically developing infants do not show consistent patterns of postural reorganization but show individual muscular strategies during the transition to independent walking. However, signs of reorganization of general motor behaviour are present.

WHAT THIS PAPER ADDS

Infants show signs of reorganization of motor behaviour when learning to walk. Infants show individual strategies of postural reorganization when learning to walk.

Early Intervention and Postural Adjustments During Reaching in Infants at Risk of Cerebral Palsy

PURPOSE

To investigate postural effects of the family-centered program, COPing with and CAring for infants with special needs (COPCA), applied at 3 to 6 months' corrected age in infants at high risk of cerebral palsy. Previously, we reported postural differences between the infants at risk of CP in the control group of the current study and a group of infants developing typically. Now we focus on differences between 2 intervention groups.

METHODS

We explored postural adjustments during reaching in seated infants at 4, 6, and 18 months using surface electromyography of arm, neck, and trunk muscles. Infants randomly received the family-centered program or another infant physical therapy. Using videotaped intervention sessions, we investigated correlations between time spent on specific physical therapeutic actions and direction specificity, recruitment order, and anticipatory activation at 18 months.

RESULTS

Postural adjustments in both groups were similar, but development of direction specificity and anticipatory activation in COPCA infants better mimicked typical development. These 2 parameters were associated with COPCA-type physical therapeutic actions.

CONCLUSIONS

Postural control was similar after both interventions. Positive outcomes were associated with fewer intervening actions of the therapist and greater allowance of spontaneous movements.

Brain network connectivity associated with anticipatory postural control in children and adults

Internal models provide a coherent framework for understanding motor behavior. Examples for the use of internal models include anticipatory postural adjustments (APAs), where the individual anticipates and cancels out the destabilizing effect of movement on body posture. Yet little is known about the functional changes in the brain supporting the development of APAs. Here, we addressed this issue by relating individual differences in APAs as assessed during bimanual load lifting to interindividual variation in brain network interactions at rest. We showed that the strength of the connectivity between three main canonical brain networks, namely the cingulo-opercular, the fronto-parietal and the somatosensory-motor networks, is an index of the ability to implement APAs from late childhood (9- to 11-year-old children). We also found an effect of age on the relationship between APAs and coupling strength between these networks, consistent with the notion that APAs are near but not yet fully mature in children. We discuss the implications of these findings for our understanding of learning disorders with impairment in predictive motor control.

Development of postural control in infancy in cerebral palsy and cystic periventricular leukomalacia

BACKGROUND

Development of postural problems in Cerebral Palsy (CP) is largely unknown. Postural muscle activity is organized into two levels: 1) direction-specificity; 2) fine-tuning of direction-specific activity.

AIM

To study development of postural control until 21 months corrected age in subgroups of infants at very high-risk (VHR) of CP: a) with and without CP at 21 months; b) with and without cystic periventricular leukomalacia (cPVL), the brain lesion with highest risk of CP.

METHODS AND PROCEDURES

Longitudinal electromyography recordings of postural muscles during reaching were made in 38 VHR-infants (severe brain lesion or clear neurological signs) between 4.7 and 22.6 months (18 CP, of which 8 with cPVL). Developmental trajectories were calculated using linear mixed effect models.

OUTCOMES AND RESULTS

VHR-infants with and without CP showed virtually similar postural development throughout infancy. The subgroup of VHR-infants with cPVL improved performance in direction-specificity with increasing age, while they performed throughout infancy worse in fine-tuning of postural adjustments than infants without cPVL.

CONCLUSIONS AND IMPLICATIONS

VHR-infants with and without CP have a similar postural development that differs from published trajectories of typically developing infants. Infants with cPVL present from early age onwards dysfunctions in fine-tuning of postural adjustments; they focus on direction-specificity.

Early human motor development: From variation to the ability to vary and adapt

This review summarizes early human motor development. From early fetal age motor behavior is based on spontaneous neural activity: activity of networks in the brainstem and spinal cord that is modulated by supraspinal activity. The supraspinal activity, first primarily brought about by the cortical subplate, later by the cortical plate, induces movement variation. Initially, movement variation especially serves exploration; its associated afferent information is primarily used to sculpt the developing nervous system, and less to adapt motor behavior. In the next phase, beginning at function-specific ages, movement variation starts to serve adaptation. In sucking and swallowing, this phase emerges shortly before term age. In speech, gross and fine motor development, it emerges from 3 to 4 months post-term onwards, i.e., when developmental focus in the primary sensory and motor cortices has shifted to the permanent cortical circuitries. With increasing age and increasing trial-and-error exploration, the infant improves its ability to use adaptive and efficicient forms of upright gross motor behavior, manual activities and vocalizations belonging to the native language.

Feedforward motor control in developmental dyslexia and developmental coordination disorder: Does comorbidity matter?

BACKGROUND AND AIM

Feedforward and online controls are two facets of predictive motor control from internal models, which is suspected to be impaired in learning disorders. We examined whether the feedforward component is affected in children (8-12 years) with developmental dyslexia (DD) and/or with developmental coordination disorder (DCD) compared to typically developing (TD) children.

METHODS

Children underwent a bimanual unloading paradigm during which a load supported to one arm, the postural arm, was either unexpectedly unloaded by a computer or voluntary unloaded by the subject with the other arm.

RESULTS

All children showed a better stabilization (lower flexion) of the postural arm and an earlier inhibition of the arm flexors during voluntary unloading, indicating anticipation of unloading. Between-group comparisons of kinematics and electromyographic activity of the postural arm revealed that the difference during voluntary unloading was between DD-DCD children and the other groups, with the former showing a delayed inhibition of the flexor muscles.

CONCLUSION

Deficit of the feedforward component of motor control may particularly apply to comorbid subtypes, here the DD-DCD subtype. The development of a comprehensive framework for motor performance deficits in children with learning disorders will be achieved only by dissociating key components of motor prediction and focusing on subtypes and comorbidities.

The tonic response to the infant knee jerk as an early sign of cerebral palsy

BACKGROUND

Early identification of infants at risk of cerebral palsy (CP) is desirable in order to provide early intervention. We previously demonstrated differences in knee jerk responses between 3-month-old high risk and typically developing infants.

AIMS

To improve early identification by investigating whether the presence of tonic responses (continuous muscle activity occurring after the typical phasic response), clonus or contralateral responses to the knee jerk during infancy is associated with CP.

STUDY DESIGN

Longitudinal EMG-study.

SUBJECTS

We included 34 high-risk infants (median gestational age 31.9 weeks) who participated in the LEARN2MOVE 0-2 years trial.

OUTCOME MEASURES

Video-recorded knee jerk EMG-assessments were performed during infancy (1-4 times). Developmental outcome was assessed at 21 months corrected age (CA). Binomial generalized estimating equations models with repeated measurements were fitted using predictor variables.

RESULTS

Infants who later were diagnosed with CP (n = 18) showed more often than infants who were not diagnosed with CP i) tonic responses - from 4 months CA onwards, ii) clonus - from 13 months CA onwards, and iii) contralateral responses - from 15 months CA onwards.

LIMITATIONS

The main limitation is the relatively small sample size.

CONCLUSIONS

The assessment of tonic responses to the knee jerk using EMG may be a valuable add-on tool to appraise a high risk of CP.

Are postural adjustments during reaching related to walking development in typically developing infants and infants at risk of cerebral palsy?

BACKGROUND

In typical development, postural adjustments during reaching change in the second half of infancy, including increasing rates of direction-specific adjustments. These changes are absent or different in infants at risk of cerebral palsy (CP). To discover whether these changes are related to acquisition of independent walking, we studied postural adjustments during reaching in infants before and after they learned to walk.

METHODS

Ten typically developing (TD) infants and 11 infants at very high risk (VHR) of CP were assessed before and after they learned to walk. Reaching movements were elicited during supported sitting, while surface electromyography was recorded of arm, neck, and trunk muscles. Percentages of direction-specific adjustments (first level of control), and recruitment patterns and anticipatory activation (second level of control) were calculated.

RESULTS

In both groups, postural adjustments during reaching were similar before and after acquisition of independent walking. Direction-specificity increased with age in typically developing infants but not in VHR-infants.

CONCLUSION

Increasing age rather than the transition to independent walking is associated with increasing direction-specificity of TD-infants during reaching while sitting, while infants at very high risk of CP show no increase in direction-specificity, suggesting that they gradually grow into a postural deficit.

Best seating condition in children with spastic cerebral palsy: One type does not fit all

BACKGROUND

The effect of forward-tilting of the seat surface and foot-support in children with spastic cerebral palsy (CP) is debated.

AIM

To assess the effect of forward-tilting of the seat surface and foot-support in children with CP on kinematic head stability and reaching.

METHODS

Nineteen children functioning at Gross Motor Function Classification System levels I-III participated [range 6-12y; ten unilateral spastic CP (US-CP) and nine bilateral spastic CP (BS-CP)]. Kinematic data were recorded of head sway and reaching with the dominant arm in four sitting conditions: a horizontal and a 15° forward (FW) tilted seat surface, each with and without foot-support.

RESULTS

Seating condition did not affect head stability during reaching, but did affect kinematic reaching quality. The major reaching parameters, i.e., the proportion of reaches with one movement unit (MU) and the size of the transport MU, were not affected by foot-support. Forward-tilting had a positive effect on these parameters in children with US-CP, whereas the horizontal condition had this effect in children with BS-CP.

IMPLICATIONS

A 15° forward-tilted seating and foot-support do not affect head stability. Reaching in children with US-CP profits from forward-tilting; in children with BS-CP forward-tilting worsens reaching - effects that are independent of foot-support.

Development of the quality of reaching in infants with cerebral palsy: a kinematic study

AIM

To assess development of reaching and head stability in infants at very high risk (VHR-infants) of cerebral palsy (CP) who did and did not develop CP.

METHOD

This explorative longitudinal study assessed the kinematics of reaching and head sway in sitting in 37 VHR-infants (18 CP) one to four times between 4.7 months and 22.6 months corrected age. Developmental trajectories were calculated using linear mixed effect models. Motor function was evaluated with the Infant Motor Profile (IMP) around 13 months corrected age.

RESULTS

Throughout infancy, VHR-infants with CP had a worse reaching quality than infants without CP, reflected for example by more movement units (factor 1.52, 95% CI 1.16-1.99) and smaller transport movement units (factor 1.86, 95% CI 1.20-2.90). Total head sway of infants with and without CP was similar, but infants with CP used more head movement units to achieve stability. The rate of developmental change in infants with and without CP was similar. Around 13 months, head control and reaching quality were interrelated; both were associated with IMP-scores.

INTERPRETATION

Infants with CP showed a worse kinematic reaching quality and head stability throughout infancy from early age onwards than VHR-infants without CP, implying that kinematically they do not grow into a deficit, but exhibit deficits from early infancy on.

WHAT THIS PAPER ADDS

Reaching quality improves throughout infancy in all infants at high risk (VHR-infants). Infants with cerebral palsy (CP) show a worse reaching quality than VHR-infants without CP. Infants with CP achieve head stability differently from infants without CP. Infants with CP exhibit kinematic reaching problems from early age onwards.

Behavioral flexibility in learning to sit

What do infants learn when they learn to sit upright? We tested behavioral flexibility in learning to sit-the ability to adapt posture to changes in the environment-in 6- to 9-month-old infants sitting on forward and backward slopes. Infants began with slant at 0°; then slant increased in 2° increments until infants lost balance. Infants kept balance on impressively steep slopes, especially in the forward direction, despite the unexpected movements of the apparatus. Between slant adjustments while the slope was stationary, infants adapted posture to the direction and degree of slant by leaning backward on forward slopes and forward on backward slopes. Postural adaptations were nearly optimal for backward slopes. Sitting experience predicted greater postural adaptations and increased ability to keep balance on steeper changes of slant, but only for forward slopes. We suggest that behavioral flexibility is integral to learning to sit and increases with sitting experience.

Body Posture Asymmetry in Prematurely Born Children at Six Years of Age

Aims

The purpose of the study was to assess body posture asymmetries in the standing and sitting position in prematurely born children at six years of age.

Study Design and Subjects

We measured trunk symmetry in coronal plane. The study was carried out in a group of 101 children, aged 6-7 years, mean age of 6.63, including 50 preterm children born at gestational age <32 weeks (preterm group) and 51 full-term children (control group).

Outcome Measures

Trunk symmetry in coronal plane was measured using photogrammetric technique with Mora 4G CQ Elektronik. The subjects were examined in standing and sitting position. Statistical analyses were carried out using Shapiro-Wilk W-test, Student's t-test, Mann–Whitney U test, and Pearson's chi-squared test. Statistical significance was assumed at p < 0.05.

Results

No significant differences were found between the groups in the asymmetries identified in the relevant anthropometric points, relative to the position assumed during the examination or to the subjects' sex.

Conclusions

There are no significant differences in body posture in the coronal plane, between preterm children and full-term children. Premature birth does not have adverse effects related to body posture asymmetry in preterm children at the age of six.

Effect of Biomechanical Constraints on Neural Control of Head Stability in Children With Moderate to Severe Cerebral Palsy

BACKGROUND

External support has been viewed as an important biomechanical constraint for children with deficits in postural control. Nonlinear analysis of head stability may be helpful to confirm benefits of interaction between external trunk support and level of trunk control.

OBJECTIVE

The purpose of this study was to compare the effect of biomechanical constraints (trunk support) on neural control of head stability during development of trunk control.

DESIGN

This was a quasi-experimental repeated-measures study.

METHODS

Data from 15 children (4-16 years of age) with moderate (Gross Motor Function Classification System [GMFCS] IV; n=8 [4 boys, 4 girls]) or severe (GMFCS V; n=7 [4 boys, 3 girls]) cerebral palsy (CP) were compared with previous longitudinal data from infants with typical development (TD) (3-9 months of age). Kinematic data were used to document head sway with external support at 4 levels (axillae, midrib, waist, and hip). Complexity, predictability, and active degrees of freedom for both anterior-posterior and medial-lateral directions were assessed.

RESULTS

Irrespective of level of support, CP groups had lower complexity, increased predictability, and greater degrees of freedom. The effect of support differed based on the child's segmental level of control. The GMFCS V and youngest TD groups demonstrated better head control, with increased complexity and decreased predictability, with higher levels of support. The GMFCS IV group had the opposite effect, showing decreased predictability and increased complexity and degrees of freedom with lower levels of support.

LIMITATIONS

Infants with typical development and children with CP were compared based on similar segmental levels of trunk control; however, it is acknowledged that the groups differed for age, cognitive level, and motor experience.

CONCLUSIONS

The effect of external support varied depending on the child's level of control and diagnostic status. Children with GMFCS V and young infants with TD had better outcomes with external support, but external support was not enough to completely correct for the influence of CP. Children with GMFCS IV performed worse, with increased predictability and decreased complexity, when support was at the axillae or midribs, suggesting that too much support can interfere with postural sway quality.

Knee jerk responses in infants at high risk for cerebral palsy: an observational EMG study

BACKGROUND

Following our clinical observation of tonic responses in response to the knee jerk in infants at very high risk for cerebral palsy (VHR infants), we systematically studied tonic responses, clonus, and reflex irradiation. We questioned (i) whether these responses occurred more often in VHR infants than in typically developing (TD) infants, and (ii) whether they were associated with abnormal general movement quality.

METHODS

Twenty-four VHR and 26 TD infants were assessed around 3 mo corrected age. Surface electromyograms of leg, trunk, neck, and arm muscles were recorded while eliciting the knee jerk. All assessments were video-recorded.

RESULTS

VHR infants more often than TD infants showed tonic responses in the ipsilateral quadriceps and hamstring (Mann-Whitney U; P = 0.0005 and P = 0.0009), clonus (Chi-square; P = 0.0005) and phasic responses in the contralateral quadriceps and hamstring (Mann-Whitney U; P = 0.002 and P = 0.0003, respectively). Widespread reflex irradiation occurred in VHR and TD infants. Definitely abnormal general movements and stiff movements were associated with tonic responses (Mann-Whitney U; P = 0.0005, P = 0.007, respectively) and clonus (Mann-Whitney U; P = 0.003 and P = 0.0005) in the ipsilateral quadriceps.

CONCLUSION

Similar to clonus, tonic responses may be regarded as a marker of a loss of supraspinal control. Reflex irradiation primarily is a neurodevelopmental phenomenon of early ontogeny.

Therapist-Designed Adaptive Riding in Children With Cerebral Palsy: Results of a Feasibility Study

BACKGROUND

It is debatable whether adaptive riding (AR) in children with cerebral palsy (CP) improves postural control and gross motor development.

OBJECTIVE

The study aim was to explore the feasibility of an extensive assessment protocol for a randomized controlled trial of therapist-designed adaptive riding (TDAR) in children with CP, with the goals of assessing the effect on child outcomes and evaluating working mechanisms of sitting postural control.

DESIGN

A pretest-posttest group design with 2 baseline measurements was used.

METHODS

Six children (1 girl, 5 boys; age range=6-12 years, median age=8 years 9 months) with bilateral spastic CP (Gross Motor Function Classification System level III) participated. Outcomes were evaluated 3 times (T0, T1, and T2) at 6-week intervals. T0 and T1 were baseline measurements; between T1 and T2, a TDAR intervention including an integrated program of postural challenge exercises (2 times per week for 1 hour) was applied. The complex protocol included the 88-item Gross Motor Function Measure (GMFM-88) and electromyographic (EMG) recording of postural muscle activity during reaching while sitting (EMG recording at T1 and T2 only).

RESULTS

The protocol was feasible. Median GMFM-88 scores changed from 64.4 at T0 to 66.7 at T1 and from 66.7 at T1 to 73.2 at T2. The change scores for all children exceeded the minimal clinically important difference of the GMFM-88. Five of 6 children showed a decrease in stereotyped top-down recruitment between T1 and T2.

LIMITATIONS

Study limitations included the lack of a control group, small sample size, and potential assessor bias for all but the EMG parameters.

CONCLUSIONS

The feasibility of the complex protocol was established. The data suggested that a 6-week TDAR intervention may improve gross motor function and may reduce stereotyped postural adjustments in children with CP. The limited results warrant replication in a well-powered randomized controlled trial.

Development of postural adjustments during reaching in infants at risk for cerebral palsy from 4 to 18 months

AIM

To investigate postural adjustments during reaching in infants at high risk for cerebral palsy (CP).

METHOD

Observational cohort study in which 25 infants at high risk (11 males, 14 females) and 11 infants with typical development (six males, five females) were assessed at 4, 6, and 18 months corrected age. Reaching movements were elicited during supported and unsupported sitting, while surface electromyography was recorded of arm, neck, and trunk muscles. Percentages of direction-specific adjustments (first level of control), and recruitment patterns and anticipatory activation (second level of control) were calculated. Statistical analyses were performed with a binomial generalized estimating equations model for dichotomous variables and a linear mixed model for continuous variables.

RESULTS

Postural activity of infants at high risk for CP at 4 months was virtually similar to that of infants with typical development. At 18 months, infants at high risk differed from infants with typical development with less direction-specificity (median values 20% vs 58% at trunk and neck level, OR 0.38, 95% CI 0.18-0.82); longer latencies to trunk muscle activation; and less anticipatory activation (41% vs 55%, in any direction-specific muscle, OR 0.53, 95% CI 0.32-0.89). In unsupported sitting, results were largely similar to those in supported sitting.

INTERPRETATION

Infants at high risk for CP grew into a postural deficit: at 18 months they showed delayed development of direction-specificity, and postural dysfunction as evidenced by slower recruitment of postural muscles and less frequent anticipatory activation.

The development of trunk control and its relation to reaching in infancy: a longitudinal study

The development of reaching is crucially dependent on the progressive control of the trunk, yet their interrelation has not been addressed in detail. Previous studies on seated reaching evaluated infants during fully supported or unsupported conditions; however, trunk control is progressively developed, starting from the cervical/thoracic followed by the lumbar/pelvic regions for the acquisition of independent sitting. Providing external trunk support at different levels to test the effects of controlling the upper and lower regions of the trunk on reaching provides insight into the mechanisms by which trunk control impacts reaching in infants. Ten healthy infants were recruited at 2.5 months of age and tested longitudinally, until 8 months. During the reaching test, infants were placed in an upright seated position and an adjustable support device provided trunk fixation at pelvic and thoracic levels. Kinematic and electromyographic data were collected. Results showed that prior to independent sitting, postural instability was higher when infants were provided with pelvic compared to thoracic support. Associated reaches were more circuitous, less smooth and less efficient. In response to the instability, there was increased postural muscle activity and arm muscle co-activation. Differences between levels of support were not observed once infants acquired independent sitting. These results suggest that trunk control is acquired in a segmental sequence across the development of upright sitting, and it is tightly correlated with reaching performance.

Postural adjustments in infants at very high risk for cerebral palsy before and after developing the ability to sit independently

BACKGROUND

Children with cerebral palsy (CP) have impaired postural control. Posture is controlled in two levels: direction-specificity, and fine-tuning of direction-specific adjustments, including recruitment order. Literature suggests that direction-specificity might be a prerequisite for independent sitting.

AIM

To study development of postural adjustments in infants at very high risk for CP (VHR-infants) during developing the ability to sit independently.

METHOD

In a longitudinal study surface electromyograms of the neck-, trunk- and arm muscles of 11 VHR-infants and 11 typically developing (TD) infants were recorded during reaching in sitting before and after developing the ability to sit unsupported (median ages: VHR 8.0 and 14.9months; TD 5.7 and 10.4months). Sessions were video-recorded.

RESULTS

In VHR- and TD-infants the prevalence of direction-specific adjustments and recruitment order did not change when the infant learned to sit independently. In VHR-infants able to sit independently more successful reaching was associated with a higher frequency of bottom-up recruitment (Spearman's rho=0.828, p=0.006) and a lower frequency of simultaneous recruitment (Spearman's rho=-0.701, p=0.035), but not with more direction-specificity. In TD-infants not able to sit independently, more successful reaching was associated with higher rates of direction-specific adjustments at the neck level (Spearman's rho=0.778, p=0.014), but not with recruitment order.

CONCLUSIONS

In VHR- and TD-infants postural adjustments during reaching in terms of direction-specificity and recruitment order are not related to development of independent sitting. Postural adjustments are associated with success of reaching, be it in a different way for VHR- and TD-infants.

CLINICAL TRIAL REGISTRATION NUMBER

NTR1428.

Typical and atypical development of reaching and postural control in infancy

Successful reaching requires postural control, either by active regulation or by postural support. The present paper reviews literature on typical and atypical development of reaching and postural control during infancy. Typically, reaching movements end in grasping around 4 months of age. Initially, reaches are characterized by large variation, including many trajectory corrections. During the first year, the movements get increasingly straight and smooth. Reaching in low-risk preterm infants is initially characterized by advanced development, but minor impairments may emerge in the second half of infancy. In high-risk preterm infants, development of reaching is characterized by delay and non-optimal reaching performance. Typical development of postural adjustments is characterized by variation and an increasing ability to adapt the variable repertoire to the specifics of the situation. The latter is facilitated by an increasing role of anticipatory mechanisms in the second half of infancy. Atypically developing infants may have a reduced repertoire and usually have difficulties in adapting postural adjustments. In infancy, most reaching movements are performed during sitting. The postural challenge of sitting may interfere in particular with the development of reaching in atypically developing infants. The practical implications of this suggestion are discussed.

Segmental trunk control acquisition and reaching in typically developing infants

This study explored the influence of an external support at the thoracic and pelvic level of the trunk on the success of reaching, postural stability and reaching kinematics while infants reached for a toy. Seventeen infants (4-6 months) were clustered into two groups according to their trunk control assessed with the Segmental Assessment of Trunk Control. Major differences were seen between groups with pelvic support, whereas with thoracic support, all infants showed similar quality reaching behaviors. With the external pelvic support, infants who had acquired trunk control in the lumbar region were more accurate in their reaching movements (less movement time, improved straightness of reach, less movement units and increased path length per movement unit) and were more stable (decreased trunk and head displacement) during a reach than infants who had only acquired trunk control in the thoracic region. These results support the hypothesis that trunk control influences the quality of reaching behavior.

Independent walking as a major skill for the development of anticipatory postural control: evidence from adjustments to predictable perturbations

Although there is suggestive evidence that a link exists between independent walking and the ability to establish anticipatory strategy to stabilize posture, the extent to which this skill facilitates the development of anticipatory postural control remains largely unknown. Here, we examined the role of independent walking on the infants' ability to anticipate predictable external perturbations. Non-walking infants, walking infants and adults were sitting on a platform that produced continuous rotation in the frontal plane. Surface electromyography (EMG) of neck and lower back muscles and the positions of markers located on the platform, the upper body and the head were recorded. Results from cross-correlation analysis between rectified and filtered EMGs and platform movement indicated that although muscle activation already occurred before platform movement in non-walking infants, only walking infants demonstrated an adult-like ability for anticipation. Moreover, results from further cross-correlation analysis between segmental angular displacement and platform movement together with measures of balance control at the end-points of rotation of the platform evidenced two sorts of behaviour. The adults behaved as a non-rigid non-inverted pendulum, rather stabilizing head in space, while both the walking and non-walking infants followed the platform, behaving as a rigid inverted pendulum. These results suggest that the acquisition of independent walking plays a role in the development of anticipatory postural control, likely improving the internal model for the sensorimotor control of posture. However, despite such improvement, integrating the dynamics of an external object, here the platform, within the model to maintain balance still remains challenging in infants.