Persistent handwriting problems are hard to predict: A longitudinal study of the development of handwriting in primary school

BACKGROUND

After one year of tuition, up to a third of primary school children show insufficient handwriting. It is unclear whether this early insufficient handwriting predicts persistent handwriting problems, because there is a dearth of studies that followed developmental trajectories longitudinally.

AIMS

To describe handwriting development in primary school children longitudinally and to determine predictive positive value and sensitivity of early handwriting assessment. To analyse whether underlying abilities helps early identification of persistent handwriting problems.

METHODS

173 primary school children were yearly assessed for four years using the Concise Assessment Scale for Children's Handwriting and the Beery Buktenica developmental test of visual-motor integration.

RESULTS

Both quality and speed of handwriting increased with years of tuition, with a pronounced increase in quality between two and three years of writing tuition. Sensitivity and positive predictive value were low. The only significant predictor of handwriting quality was handwriting quality in the previous year. For handwriting speed, no significant developmental model was revealed.

CONCLUSIONS

Quality and speed of handwriting after one year of tuition is not sufficiently predictive for distinguishing between transient insufficient handwriting and persistent handwriting problems three years later. Practitioners should hold back when referring children for remedial teaching.

Deliberately Light Interpersonal Contact Affects the Control of Head Stability During Walking in Children and Adolescents With Cerebral Palsy

OBJECTIVE

To evaluate the potential of deliberately light interpersonal touch (IPT) for reducing excessive head and trunk sway during self-paced walking in children and adolescents with cerebral palsy (CP).

DESIGN

Quasi-experimental, proof-of-concept study with between-groups comparison.

SETTING

Ambulant care facility, community center.

PARTICIPANTS

Children and adolescents (N=65), consisting of those with CP (spastic and ataxic, n=26; Gross Motor Function Classification System I-III; mean age, 9.8y; 11 girls, 15 boys) and those who were typically developed (TD, n=39; mean age, 10.0y; 23 girls, 16 boys).

INTERVENTIONS

IPT applied by a therapist to locations at the back and the head.

MAIN OUTCOME MEASURES

As primary outcomes, head and trunk sway during self-paced walking were assessed by inertial measurement units. Secondary outcomes were average step length and gait speed.

RESULTS

CP group: apex and occiput IPT reduced head velocity sway compared with thoracic IPT (both P=.04) irrespective of individuals' specific clinical symptoms. TD group: all testing conditions reduced head velocity sway compared with walking alone (all P≤.03), as well as in apex and occiput IPT compared with paired walking (both P≤.02).

CONCLUSIONS

Deliberately light IPT at the apex of the head alters control of head sway in children and adolescents with CP. The effect of IPT varies as a function of contact location and acts differently in TD individuals.

Reflections on Mirror Therapy

Background. Mirror visual feedback (MVF), a phenomenon where movement of one limb is perceived as movement of the other limb, has the capacity to alleviate phantom limb pain or promote motor recovery of the upper limbs after stroke. The tool has received great interest from health professionals; however, a clear understanding of the mechanisms underlying the neural recovery owing to MVF is lacking. Objective. We performed a systematic review to assess the effect of MVF on brain activation during a motor task. Methods. We searched PubMed, CINAHL, and EMBASE databases for neuroimaging studies investigating the effect of MVF on the brain. Key details for each study regarding participants, imaging methods, and results were extracted. Results. The database search yielded 347 article, of which we identified 33 suitable for inclusion. Compared with a control condition, MVF increases neural activity in areas involved with allocation of attention and cognitive control (dorsolateral prefrontal cortex, posterior cingulate cortex, S1 and S2, precuneus). Apart from activation in the superior temporal gyrus and premotor cortex, there is little evidence that MVF activates the mirror neuron system. MVF increases the excitability of the ipsilateral primary motor cortex (M1) that projects to the “untrained” hand/arm. There is also evidence for ipsilateral projections from the contralateral M1 to the untrained/affected hand as a consequence of training with MVF. Conclusion. MVF can exert a strong influence on the motor network, mainly through increased cognitive penetration in action control, though the variance in methodology and the lack of studies that shed light on the functional connectivity between areas still limit insight into the actual underlying mechanisms.

Postural adaptation during arm raising in children with and without unilateral cerebral palsy

Postural sway during arm movements were related to the size of the base of support (BOS) and the limits of stability (LOS) of children with unilateral cerebral palsy (USCP) and typically developing (TD) children. For half of the trials the mechanical disturbance due to the rapid arm movement was increased by attaching small weights at the wrists. The participants stood with both feet on a large force plate, which recorded the displacements of the center of pressure (CoP). The results showed that in the children with USCP the LOS forward and toward the non-dominant (more-affected) side were smaller than in the TD children whereas the LOS backward and toward the dominant (less-affected) side did not differ between the two groups. When rapidly moving the arms the children with USCP swayed over a larger portion of their base of support in the forward direction and toward their more-affected side. In addition, the maximal sway toward the more-affected side during arm movement exceeded the LOS while balance was maintained. These effects increased when the movements were performed with the weights at the wrists. These results show that an area of permissible sway, which was not spontaneously explored during the leaning task, was required to maintain balance during the supra-postural task. Training to enlarge the LOS that includes weight shifts toward the more-affected side might reduce the area of the BOS that is self-perceived as less secure.

Upper limb activity in children with unilateral spastic cerebral palsy: the role of vision in movement strategies

This article reviews the capacity of children with unilateral spastic cerebral palsy (USCP) to (re)organize the available degrees of freedom and to use visual information in interceptive actions during motion with either the impaired or the less-impaired hand. Atypical reaching movements, such as increased trunk movement or slower wrist velocity, are considered adaptive coordination patterns that are the result of a change in the constraints. It is argued that manipulation of the task context facilitates children with USCP to enhance performance. For example, when reducing the time available to intercept a ball, the children are found to exceed their usual maximum walking speed and to increase range of motion of the elbow. In addition, the children appear to rely on a visual information strategy similar to typically developing children ('bearing angle'), although more variability is observed when using the impaired arm. The implications for interventions are, it should be recognized, that these children adapt to the impairment by reorganizing the movement system and that this process can be influenced by changing the task context. Attention should be paid to the importance of using correct visual cues for initiation and guidance of interceptive actions, which may be provoked by using external visual triggers.

Practicing a matching movement with a mirror in individuals with spastic hemiplegia

This experimental study aimed to determine the effect of practicing a position matching task with (mirror) visual feedback of the less-impaired arm on the matching accuracy of the impaired arm in children and adolescents with spastic hemiparetic cerebral palsy. Practice consisted of 40 trials of bimanual target matching, where one group received regular visual feedback and a second group received mirror visual feedback of the less-impaired arm. On three occasions (pre, post, and after a 1-week-retention) position sense (matching accuracy measured as the endpoint error in cm) of the impaired arm was tested with a unimanual and bimanual matching task, performed without any visual information of either hand. Matching accuracy of the impaired arm was better in the post-test than in the pre-test, but this improvement was similar for both practice groups. In the retention-test, accuracy had returned to pre-test-level, which might be ascribed to the short duration of the practice period. These outcomes suggest that practicing a matching task with visual feedback of the less-impaired arm might help to improve the matching accuracy of the impaired arm in individuals with spastic hemiparetic cerebral palsy.

Matching accuracy in hemiparetic cerebral palsy during unimanual and bimanual movements with (mirror) visual feedback

In the present study participants with Spastic Hemiparetic Cerebral Palsy (SHCP) were asked to match the position of a target either with the impaired arm only (unimanual condition) or with both arms at the same time (bimanual condition). The target was placed at 4 different locations scaled to the individual maximum reaching distance. To test the effect of mirror visual feedback of the less-impaired arm on the matching accuracy, an opaque screen or a mirror was placed in between the arms which masked vision of the impaired arm. Absolute endpoint error was smaller in the bimanual condition compared to the unimanual condition, but there was no effect of mirror visual feedback. Inspection of the individual data, however, showed that 13 out of 23 participants did experience a positive effect of mirror visual feedback. A positive correlation between the baseline error (screen) and the improvement in accuracy with mirror visual feedback seems to suggest that individuals with lower proprioceptive accuracy in the baseline condition may benefit more from mirror visual feedback. Together these findings indicate that bimanual therapy and therapy with mirror visual feedback might be valuable approaches for rehabilitation for a subset of the individuals with SHCP.

Deficits in upper limb position sense of children with Spastic Hemiparetic Cerebral Palsy are distance-dependent

This study examined the arm position sense in children with Spastic Hemiparetic Cerebral Palsy (SHCP) and typically developing children (TD) by means of a contralateral matching task. This task required participants to match the position of one arm with the position of the other arm for different target distances and from different starting positions. Results showed that children with SHCP exhibited with both arms larger matching errors than the TD group, but only when the distance between the arms at the start of the movement was large. In addition, the difference in errors between the less-impaired and the impaired limb changed as a function of the distance in the SHCP group whereas no interlimb differences were found in the TD group. Finally, spasticity and restricted range of motion in children with SHCP were not related to the proportion of undershoot and size of absolute error. This suggests that SHCP could be associated with sensory problems in conjunction with their motor problems. In conclusion, the current study showed that accurate matching of the arms is greatly impaired in SHCP when compared to TD children, irrespective of which arm is used. Moreover, this deficit is particularly present for large movement amplitudes.

Gaze behaviour during interception in children with spastic unilateral cerebral palsy

Anticipatory gaze behaviour during interceptive movements was investigated in children with Spastic Unilateral Cerebral Palsy (SUCP), and related to the side of the intracerebral lesion. Five children with lesions of the right hemisphere (RHL) and five children with lesions of the left hemisphere (LHL) had to walk towards and intercept a ball that moved perpendicular to the walking path. Interception accuracy and gaze patterns were measured in a no-occlusion and occlusion condition, in which the ball was occluded from view for half of its trajectory. There was a clear support for a relationship between gaze behaviour and success in interception performance, with some evidence for the presence of anticipatory gaze behaviour. There were also differences in gaze behaviour between children with RHL and children with LHL that might be related to planning, but these did not affect interception accuracy. It is concluded that gaze behaviour during interceptive movements is anticipatory, and at least partly dependent on the lesional side.

The positive effect of mirror visual feedback on arm control in children with spastic hemiparetic cerebral palsy is dependent on which arm is viewed

Mirror visual feedback has previously been found to reduce disproportionate interlimb variability and neuromuscular activity in the arm muscles in children with Spastic Hemiparetic Cerebral Palsy (SHCP). The aim of the current study was to determine whether these positive effects are generated by the mirror per se (i.e. the illusory perception of two symmetrically moving limbs, irrespective of which arm generates the mirror visual feedback) or by the visual illusion that the impaired arm has been substituted and appears to move with less jerk and in synchrony with the less-impaired arm (i.e. by mirror visual feedback of the less-impaired arm only). Therefore, we compared the effect of mirror visual feedback from the impaired and the less-impaired upper limb on the bimanual coupling and neuromuscular activity during a bimanual coordination task. Children with SHCP were asked to perform a bimanual symmetrical circular movement in three different visual feedback conditions (i.e. viewing the two arms, viewing only one arm, and viewing one arm and its mirror image), combined with two head orientation conditions (i.e. looking from the impaired and looking from the less-impaired body side). It was found that mirror visual feedback resulted in a reduction in the eccentric activity of the Biceps Brachii Brevis in the impaired limb compared to the condition with actual visual feedback from the two arms. More specifically, this effect was exclusive to mirror visual feedback from the less-impaired arm and absent when mirror visual feedback from the impaired arm was provided. Across conditions, the less-impaired arm was the leading limb, and the nature of this coupling was independent from visual condition or head orientation. Also, mirror visual feedback did not affect the intensity of the mean neuromuscular activity or the muscle activity of the Triceps Brachii Longus. It was concluded that the positive effects of mirror visual feedback in children with SHCP are not just the result of the perception of two symmetrically moving limbs. Instead, in order to induce a decrease in eccentric neuromuscular activity in the impaired limb, mirror visual feedback from the ‘unaffected’ less-impaired limb is required.

Visual feedback of the non-moving limb improves active joint-position sense of the impaired limb in Spastic Hemiparetic Cerebral Palsy

This study examined the active joint-position sense in children with Spastic Hemiparetic Cerebral Palsy (SHCP) and the effect of static visual feedback and static mirror visual feedback, of the non-moving limb, on the joint-position sense. Participants were asked to match the position of one upper limb with that of the contralateral limb. The task was performed in three visual conditions: without visual feedback (no vision); with visual feedback of the non-moving limb (screen); and with visual feedback of the non-moving limb and its mirror reflection (mirror). In addition to the proprioceptive measure, a functional test [Quality of Upper Extremity Skills Test (QUEST)] was performed and the amount of spasticity was determined in order to examine their relation with proprioceptive ability. The accuracy of matching was significantly influenced by the distance that had to be covered by the matching limb; a larger distance resulted in a lower matching accuracy. Moreover it was demonstrated that static (mirror) visual feedback improved the matching accuracy. A clear relation between functionality, as measured by the QUEST, and active joint-position sense was not found. This might be explained by the availability of visual information during the performance of the QUEST. It is concluded that static visual feedback improves matching accuracy in children with SHCP and that the initial distance between the limbs is an influential factor which has to be taken into account when measuring joint-position sense.

Visual guidance of interceptive actions in children with spastic unilateral cerebral palsy is influenced by the side of the lesion

PURPOSE

To determine the type of visual information used by children with spastic unilateral cerebral palsy (SUCP) in order to intercept a ball and to verify whether this information was dependent on the side of the lesion. More specifically, it was examined whether the interception was controlled on the basis of a time or a distance strategy, initiating the catch when the ball is at a fixed time interval or at a fixed distance from the point of interception.

METHODS

Three groups of children were included. Children with either a left sided (LHL) or a right sided lesion (RHL) and children without a lesion [typically developing (TD)] intercepted a ball from a conveyor belt. In order to intercept the ball successfully they had to walk and to reach for the ball at the interception point 4 m away.

RESULTS

Children with LHL had a longer decision time and started their reach movement earlier. In 56% of the children with LHL a distance strategy was observed, while in the TD and the children with RHL predominantly a time strategy was found.

CONCLUSIONS

The side of the lesion influences the visual information used to initiate interceptive actions.

Mirror visual feedback induces lower neuromuscular activity in children with spastic hemiparetic cerebral palsy

The study examined the effects of mirror feedback information on neuromuscular activation during bimanual coordination in eight children with spastic hemiparetic cerebral palsy (SHCP) and a matched control group. The 'mirror box' creates a visual illusion, which gives rise to a visual perception of a zero lag, symmetric movement between the two arms. The study incorporated two additional visual feedback conditions by placing a glass or opaque screen between the arms. During bilateral symmetric circular arm movements mirror visual feedback induced lower neuromuscular intensities in the shoulder muscles of the less impaired arm of children with SHCP compared to the other visual conditions. In addition, the mirror lead to shorter relative durations of eccentric and concentric activity in the elbow muscles of the more impaired arm, whereas no effects of visual feedback were found in a matched control group. These results suggest that replacing veridical visual information of the more impaired arm with a mirror reflection of the less impaired arm improves the motor control of children with SHCP during interlimb coupling. The effects of the availability of visual feedback in individuals with hemiparesis are discussed with reference to: (1) increase ipsilateral motor cortex excitability and (2) congruence between afferent (visual) feedback and the internal copy of the motor commands.

Patterns of postural sway in high anxious children

Background

Current research suggests that elevated levels of anxiety have a negative impact on the regulation of balance. However, most studies to date examined only global balance performance, with little attention to the way body posture is organized in space and time. The aim of this study is to examine whether posturographic measures can reveal (sub)clinical balance deficits in children with high levels of anxiety.

Methods

We examined the spatio-temporal structure of the centre-of-pressure (COP) fluctuations in children with elevated levels of anxiety and a group of typically developing children while maintaining quiet stance on a force plate in various balance challenging conditions. Balance was challenged by adopting sensory manipulations (standing with eyes closed and/or standing on a foam surface) and using a cognitive manipulation (dual-tasking).

Results

Across groups, postural performance was strongly influenced by the sensory manipulations, and hardly by the cognitive manipulation. We also found that children with anxiety had overall more postural sway, and that their postural sway was overall less complex than sway of typically developing children. The postural differences between groups were present even in the simple baseline condition, and the group differences became larger with increasing task difficulty.

Conclusion

The pattern of postural sway suggests that balance is overall less stable and more attention demanding in children with anxiety than typically developing children. The findings provide further evidence for a neuro-behavioral link between psychopathology and the effectiveness of postural control.

Is there an effect of prenatal breech position on locomotion at 2.5 years?

The long-term effects of intra-uterine breech position on postnatal development of motor functions have not been systematically investigated. The aim of the present study was to investigate the possible effect of prenatal breech position on locomotion. Two complementary studies were conducted. Firstly, a gait analysis was carried out. Secondly, in a functional task the children were challenged to cross a gap until their maximum attainable crossing distance was reached. The mean age of the twenty-one children who participated in this study was 32.1 months (SD=4). Children who had lain in prenatal breech position (n=10) had a walking pattern comparable to the control group (n=11). There were no differences in step length, step width, foot rotation, foot rotation asymmetry, hip flexion, hip extension and range of motion of the hip. Thus, prenatal breech position, although a long-term effect was found, does not seem to have functional consequences on locomotion. However, the total amount of extra hip motion during the gap crossing was significantly smaller in children who had lain in breech position compared to the control group. This was due to significant less extra hip flexion at the side of the leading leg. Nevertheless, comparable maximum gaps were crossed in both groups. Apparently, these children had a different solution of the challenging task of gap crossing. They compensated the lack of extra hip flexion by applying more extra hip extension.

Children with cerebral palsy exhibit greater and more regular postural sway than typically developing children

Following recent advances in the analysis of centre-of-pressure (COP) recordings, we examined the structure of COP trajectories in ten children (nine in the analyses) with cerebral palsy (CP) and nine typically developing (TD) children while standing quietly with eyes open (EO) and eyes closed (EC) and with concurrent visual COP feedback (FB). In particular, we quantified COP trajectories in terms of both the amount and regularity of sway. We hypothesised that: (1) compared to TD children, CP children exhibit a greater amount of sway and more regular sway and (2) concurrent visual feedback (creating an external functional context for postural control, inducing a more external focus of attention) decreases both the amount of sway and sway regularity in TD and CP children alike, while closing the eyes has opposite effects. The data were largely in agreement with both hypotheses. Compared to TD children, the amount of sway tended to be larger in CP children, while sway was more regular. Furthermore, the presence of concurrent visual feedback resulted in less regular sway compared to the EO and EC conditions. This effect was less pronounced in the CP group where posturograms were most regular in the EO condition rather than in the EC condition, as in the control group. Nonetheless, we concluded that CP children might benefit from therapies involving postural tasks with an external functional context for postural control.

NO SINGLE FACTOR HAS PRIORITY IN ACTION DEVELOPMENT A TRIBUTE TO ESTHER THELEN'S LEGACY

Among Esther Thelen's most important contributions to developmental theory is that there is no single factor that has priority in driving development. In this paper, we discuss how this notion influenced our research on perceptual-motor development. We show that multiple factors constrain perceptual-motor development, but that a relatively minor change in one of them may lead to significant changes in the observed perceptual-motor behavior.

Balance training with visual feedback in children with hemiplegic cerebral palsy: effect on stance and gait

The aim of the present study was to examine the effects of balance training with visual feedback on stance and gait in school-age children with hemiplegic cerebral palsy. Ten participants between 5 and 11 years of age were assigned to either the training or the control group according to an aged-stratified randomization. The training corresponded to three sessions per week during six weeks. Stance and gait parameters- based on force plate data, were assessed three times in both groups: (a) at the beginning of the study (before training); (b) after six weeks; (c) after ten weeks. Spatial and temporal parameters were calculated. The results for stance showed that the training improved the performances on the tasks that were trained. More interesting, the results for gait showed that the walking pattern became more symmetrical after the training.

Suppression of EMG activity by transcranial magnetic stimulation in human subjects during walking

1. The involvement of the motor cortex during human walking was evaluated using transcranial magnetic stimulation (TMS) of the motor cortex at a variety of intensities. Recordings of EMG activity in tibialis anterior (TA) and soleus muscles during walking were rectified and averaged. 2. TMS of low intensity (below threshold for a motor-evoked potential, MEP) produced a suppression of ongoing EMG activity during walking. The average latency for this suppression was 40.0 +/- 1.0 ms. At slightly higher intensities of stimulation there was a facilitation of the EMG activity with an average latency of 29.5 +/- 1.0 ms. As the intensity of the stimulation was increased the facilitation increased in size and eventually a MEP was clear in individual sweeps. 3. In three subjects TMS was replaced by electrical stimulation over the motor cortex. Just below MEP threshold there was a clear facilitation at short latency (approximately 28 ms). As the intensity of the electrical stimulation was reduced the size of the facilitation decreased until it eventually disappeared. We did not observe a suppression of the EMG activity similar to that produced by TMS in any of the subjects. 4. The present study demonstrates that motoneuronal activity during walking can be suppressed by activation of intracortical inhibitory circuits. This illustrates for the first time that activity in the motor cortex is directly involved in the control of the muscles during human walking.

Acquisition of upper body stability during walking in toddlers

This study examines the development of head and trunk movements in toddlers as they begin to walk independently. The data are from a longitudinal study of 7 infants observed from the onset of walking over a period of 46-80 weeks. Head and trunk rotations were measured in the frontal and sagittal planes together with global gait parameters (progression velocity, step cadence, length and width, duration of double support phase). The results showed that during the first weeks of walking head and trunk oscillations significantly decreased, indicating that considerable progress is made in upper body stabilization. Dramatic changes in global gait parameters also occurred at this time. After this first period of rapid changes, gait parameters continued the same developmental trend but with slower changes. The close relation between gain in head and trunk stability and improvement in walking efficacy is discussed on the basis of the individual developmental trends.

Head coordination as a means to assist sensory integration in learning to walk

After a brief presentation of the development of free walking interpreted as learning dynamical equilibrium, the problem of sensory integration in the process of walking development is discussed. A critical review of the role of vision in the development of posturo-locomotor task is presented, along with recent test results on the development of the vestibular system. A final section presents the development of head stabilization and coordination as a necessary means to assist sensory integration. It is suggested that if sensory information is necessary to enhance posturo-locomotor skills, a good mastery of walking is in turn necessary to increase the efficiency of sensory integration.

The build-up of anticipatory behaviour. An analysis of the development of gait initiation in children

This study analyses the anticipatory postural adjustments during the gait initiation process in children aged 2.5, 4, 6 and 8 years. In adults, anticipation during gait initiation includes a shift in the centre of foot pressure (CP) both backwards and towards the stepping foot. Backward displacement and the duration of the anticipation phase covary with the gait progression velocity reached by the subject at the end of the first step. In the present study, the children walked on a force plate that allowed us to calculate the acceleration of the centre of mass and the displacements of the CP. The results showed three main characteristics of the development of anticipatory behaviour: (1) The occurrence of anticipatory displacements of the CP increased progressively with age. Systematic backward anticipation was found for all children except one of the youngest, whereas the lateral displacement was systematically observed later, in the 6-year group; (2) the amplitude of the spatial parameters showed a significant increase with age; (3) contrary to the adult, the amplitude of the backward shift did not covary with the forthcoming velocity in the youngest groups. This covariation became significant at 6 years and remained significant at 8 years. The results showed that even if anticipatory behaviour was present in 2.5-year-old children it is only later that the child is able of more accurate tuning of feedforward control, probably due to better control of the overall postural adjustments.

Head coordination in the sagittal plane in toddlers during walking: preliminary results

In adults, head rotations in the pitch plane are highly synchronized with vertical head translations during different locomotor tasks as walking, running, and hopping. The head is rotating up then down in the pitch plane as stepping movement drives the head down then up, respectively. The purpose of our study was to determine at which period of the motor control development this fine head coordination occurred. The organization of head movements was analyzed in four normal children observed longitudinally from the onset of walking up to 80 weeks of independent walking (IW). The degree of synchronization between vertical head translations and head rotations in the pitch plane was used to define an index of head coordination for 15 to 25 steps per child per session. Our results show that the coordination of head rotations in the pitch plane improves continually in toddlers but does not reach the optimal level during the first year of IW experience. We showed previously that head stabilization in space was achieved during the first weeks of IW. Both head stabilization in space and fine head coordination during walking are considered as directly involved in gaze stabilization, but in toddlers head stabilization in space is completed earlier than head coordination. Head stabilization appears to be a necessary motor control to acquire prior to the development of head movement coordination.

Trunk and head stabilization during the first months of independent walking

This study measured the rate of acquisition of head and trunk postural control during the two early developmental periods of independent walking, as defined by global gait parameters. Gait parameters were observed longitudinally in four children. The maximum angular deviations of the trunk and head oscillations were computed in the frontal and sagittal planes. These decreased most dramatically during the first 10-15 weeks of independent walking, during the same period when global gait parameters changed rapidly. This head and trunk stabilization may be a fundamental process that help to maintain equilibrium during walking, and may be a necessary step prior to the development of fine posturo-motor control.