Anticipatory postural adjustments in a bimanual load‐lifting task in children with developmental coordination disorder

Aim Postural control is a fundamental component of action in which deficits have been shown to contribute to motor difficulties in children with developmental coordination disorder (DCD). The purpose of this study was to examine anticipatory postural adjustments (APAs) in children with DCD in a bimanual load‐lifting task. Method Sixteen children with reported motor problems (two females, 14 males; mean age 9y; SD 2y) and 16 typically developing, age‐matched children (six females, 10 males; mean age 9y; SD 2y) took part in the study. The task required the children to maintain a stable elbow angle, despite imposed or voluntary unloading of the forearm. APAs were assessed using electromyography and kinematics analysis. Results Although children with DCD could compensate for the consequences of unloading, the results demonstrated that APAs were less efficient in children with DCD than in typically developing children. A positive and significant coefficient of regression between the flexor inhibition latency and the postural stabilization was only found in typically developing children. Interpretation The impaired fine‐tuning of the muscle contribution and the poor stabilization performances demonstrate poor predictive modelling in DCD.     

Motor and gestural performance in children with autism spectrum disorders, developmental coordination disorder, and/or attention deficit hyperactivity disorder.

Motor and gestural skills of children with autism spectrum disorders (ASD), developmental coordination disorder (DCD), and/or attention deficit hyperactivity disorder (ADHD) were investigated. A total of 49 children with ASD, 46 children with DCD, 38 children with DCD+ADHD, 27 children with ADHD, and 78 typically developing control children participated. Motor skills were assessed with the Bruininks-Oseretsky Test of Motor Proficiency Short Form, and gestural skills were assessed using a test that required children to produce meaningful gestures to command and imitation. Children with ASD, DCD, and DCD+ADHD were significantly impaired on motor coordination skills; however, only children with ASD showed a generalized impairment in gestural performance. Examination of types of gestural errors revealed that children with ASD made significantly more incorrect action and orientation errors to command, and significantly more orientation and distortion errors to imitation than children with DCD, DCD+ADHD, ADHD, and typically developing control children. These findings suggest that gestural impairments displayed by the children with ASD were not solely attributable to deficits in motor coordination skills.     

Developmental delay of finger torque control in children with developmental coordination disorder

Aim We examined whether the behavioral impairments in finger torque control evident in children with developmental coordination disorder (DCD) follow a delayed or different developmental trajectory compared with their typically developing peers. Method Children with DCD (n=36; 18 males, 18 females; mean age 9y 7mo, SD 1y 8mo) and 36 typically developing children (15 males, 21 females; mean age 9y 7mo, SD 2y), between 6 years 10 months and 12 years 7 months of age were recruited from schools in Porto Alegre, Brazil. Particpants completed finger torque control and maximum finger torque production tasks. The inclusion criterion for children with DCD was a Movement Assessment Battery for Children score below the fifth centile. Group means and cross‐sectional age‐related landscapes of the two groups were compared. Results Children with DCD were more variable (p<0.001), less accurate (p=0.007), and less irregular (p<0.001), on average, in their finger torque control than their typically developing peers, despite producing nearly equivalent levels of maximum torque (p=0.49). Despite these mean differences, the cross‐sectional age‐related changes in torque control were similar in the two groups (all p>0.05). Interpretation The developmental trajectory of finger torque control in children with DCD, compared with typically developing children, is delayed. This suggests the behavioral deficits in finger torque control in children with DCD persist as a function of age, rather than progressing or resolving.     

Association between visual perceptual deficits and motor deficits in children with developmental coordination disorder

This study explored the relation between a motor-free visual perceptual deficit, different visual-motor integration deficits, and different motor skills in children with developmental coordination disorder (DCD). Thirty-six children (22 males), aged 9 or 10 years, with DCD and a control group (n=36), matched for age and sex, were assessed with the Movement Assessment Battery for Children (MABC), a ball-catching test, a jumping test, a timed response task to a visual moving stimulus, and the Beery-Buktenica Developmental Test of Visual-Motor Integration, incorporating copying, visual discrimination, and tracing tasks. Children with DCD performed significantly worse than the control group on all measures. The visual discrimination task did not correlate significantly with any of the motor tasks. The visual timing task correlated significantly with the ball-catching test in the DCD group. The copying test was significantly correlated with the MABC in the DCD group. The association between visual-perceptual deficits and motor tasks was shown to be task specific.     

The effectiveness of exercise intervention on inhibitory control in children with developmental coordination disorder: Using a visuospatial attention paradigm as a model

Children with developmental coordination disorder (DCD) have been demonstrated to show a deficit of inhibitory control in volitional shifts of attention. The aim of this study was to use ecological intervention to investigate the efficacy of table-tennis training on treating both problems with attentional networks and motor disorder in children with DCD. Forty-three children aged 9–10 years old were screened using the Movement Assessment Battery for Children and divided into DCD (n = 27) and typically developing (TD, n = 16) groups. Children with DCD were then quasi-randomly assigned to either a DCD-training group who underwent a ten-week table-tennis training program with a frequency of 3 times a week or a DCD non-training group. Before and after training, the capacity of inhibitory control was examined with the endogenous Posner paradigm task for DCD and TD groups. Table-tennis training resulted in significant improvement of cognitive and motor functions for the children with DCD. The study demonstrated that exercise intervention employed within the school setting can benefit the inhibitory control and motor performance in children with DCD. However, future research efforts should continue to clarify whether the performance gains could be maintained over time.     

Deficits of visuospatial attention with reflexive orienting induced by eye-gazed cues in children with developmental coordination disorder in the lower extremities: An event-related potential study

The present study aims to investigate and compare the behavioral performance and event-related potentials (ERPs) measures in children with developmental coordination disorder (DCD) and typically developing (TD) children when performing the visuospatial attention task with reflexive orienting. Thirty children with DCD and 30 TD children were recruited and presented with central eye-gazed cues. The children needed to detect and respond to laterally presented reaction signals preceded by centrally presented non-predictive directional and non-directional eye-gazed cues, which directed them to attend covertly to the right or left field location, or straight ahead, via stepping on pedals with their bilateral lower limbs, while brain ERPs were concurrently recorded. The behavioral data showed that children with DCD responded slowly and exhibited a deficit in inhibitory control capacity as compared to TD children. In terms of electrophysiological characteristics, children with DCD showed distinct modulatory effects upon longer N2 and P3 latencies, smaller P3 amplitude, an elongated interval between N2 and the motor response (N2 latency-RT), and small areas on Contingent Negative Variation (CNV). The behavioral and ERP data suggest that children with DCD could have deficits in the ventral attention network and the mechanisms on the inhibitory control difficulty, when performing such a task, could be a slower response inhibitory process and stimulus classification speed, less ability in interhemispheric and cognitive-to-motor transfer speed, and less mature abilities with regard to anticipatorily executive and motor preparatory processes.     

Everyday memory in children with developmental coordination disorder

Children with developmental coordination disorder (DCD) have deficits in working memory, but little is known about the everyday memory of these children in real-life situations. We investigated the everyday memory function in children with DCD, and explored the specific profile of everyday memory across different domains. Nineteen children with DCD and 19 typically developing (TD) children participated in the study. Their everyday memory performance was evaluated using the Rivermead Behavioral Memory Test for Children, which showed that 52.6% of the children with DCD had everyday memory deficits. The overall everyday memory scores of the DCD group were significantly lower than those of the controls, particularly in the verbal and visual memory domains. Pearson correlation analysis indicated significant associations between verbal intelligence and memory scores. Analysis of covariance with verbal intelligence as a covariate showed no significant differences between groups in memory scores. Mediator analysis supported the notion that everyday memory deficits in children with DCD were fully mediated through verbal intelligence. We provide evidence of everyday memory deficits in most of the children with DCD, and hypothesize that language abilities are their underlying cause. The clinical implications of these findings and recommendations for additional research are discussed.     

Internal representation of movement in children with developmental coordination disorder: a mental rotation task

Recent studies show that children with developmental coordination disorder (DCD) have difficulties in generating an accurate visuospatial representation of an intended action, which are shown by deficits in motor imagery. This study sought to test this hypothesis further using a mental rotation paradigm. It was predicted that children with DCD would not conform to the typical pattern of responding when required to imagine movement of their limbs. Participants included 16 children with DCD and 18 control children; mean age for the DCD group was 10 years 4 months, and for controls 10 years. The task required children to judge the handedness of single-hand images that were presented at angles between 0 degrees and 180 degrees at 45 degrees intervals in either direction. Results were broadly consistent with the hypothesis above. Responses of the control children conformed to the typical pattern of mental rotation: a moderate trade-off between response time and angle of rotation. The response pattern for the DCD group was less typical, with a small trade-off function. Response accuracy did not differ between groups. It was suggested that children with DCD, unlike controls, do not automatically enlist motor imagery when performing mental rotation, but rely on an alternative object-based strategy that preserves speed and accuracy. This occurs because these children manifest a reduced ability to make imagined transformations from an egocentric or first-person perspective.     

Assessment of body composition using whole body air-displacement plethysmography in children with and without developmental coordination disorder

Developmental coordination disorder (DCD) is a neuro-developmental disorder characterized by poor fine and/or gross motor coordination. Children with DCD are hypothesized to be at increased risk for overweight and obesity from inactivity due to their motor coordination problems. Although previous studies have found evidence to support this hypothesis, their reliance on field-based measures, most notably body mass index (BMI), to determine body composition is problematic. Moreover, there has been no research to date that has examined whether THERE ARE differences in lean tissue mass between children with and without coordination. Differences in muscle mass, the main component of lean tissue, may be a contributing factor to both coordination problems and the development of overweight and obesity, but has only been indirectly examined at this time. In this study, whole-body air displacement using a dual chamber plethysmograph was used to estimate fat mass, fat free mass and body fat in children with probable DCD (pDCD) and a group of typically developing children. Consistent with previous research using field-based assessments of relative body weight, the results show that children with pDCD have much higher body fat than their peers, and that this difference increases with the severity of observed motor coordination difficulties. There was no difference in lean tissue mass between groups. The demonstration of an association between pDCD and body fat using a more sensitive measure of body composition, and evidence showing a dose-response in this relationship, further supports the hypothesis that DCD may be a risk factor for obesity in children.     

A comparison of motor imagery performance in children with spastic hemiplegia and developmental coordination disorder

Individuals with hemiplegia have difficulty planning movements, which may stem from deficits in motor imagery ability. We explored motor imagery ability in three groups of 21 children, aged 8-12 years: children with hemiplegia; children with developmental coordination disorder (DCD); and a comparison group. They completed two tasks requiring laterality judgments of body parts--hand and whole-body rotation. Accuracy in both was reduced for the motor-impaired groups, and response time was atypical for the whole-body task. This suggests that motor imagery deficits exist in children with hemiplegia and DCD, supporting previous findings that planning deficits in hemiplegia may result from deficits in motor imagery.     

Characterization of motor control in handwriting difficulties in children with or without developmental coordination disorder

Aim The purpose of this study was to characterize handwriting deficits in children with developmental coordination disorder (DCD) using computerized movement analyses. Method Seventy‐two children (40 females, 32 males; mean age 7y, SD 7mo; range 6y 2mo to 7y 11mo) with handwriting deficits (33 with DCD, 39 without DCD); and 22 age‐ and sex‐matched children without handwriting deficits were asked to perform handwriting tasks on a digital tablet for the collection of kinematic and kinetic data. Practice times required to achieve automation of movement when writing an unfamiliar character were used to assess the motor learning of handwriting. The children were asked to copy three simple and three complex characters, and the velocity and axial pen force used for corresponding strokes were compared. Results The attainment of automated handwriting was markedly slower in children with handwriting deficits and DCD, who used a faster stroke velocity to write simple characters (1.22 times those without handwriting deficits), but when writing complex characters, their stroke velocity and pen force were lower (0.85 and 0.89 times those without handwriting deficits, respectively). Interpretation By linking the results with neuromotor control theories, it was determined that children with DCD have difficulties performing the open‐loop and closed‐loop movements required for fluent handwriting.     

Developmental coordination disorder in children with attention-deficit-hyperactivity disorder and physical therapy intervention

Although physical therapy (PT) is effective in improving motor function in children with developmental coordination disorder (DCD), insufficient data are available on the impact of this intervention in children with combined attention-deficit-hyperactivity disorder (ADHD) and DCD. This prospective study aimed to establish the prevalence of DCD among a cohort of patients with ADHD, characterize the motor impairment, identify additional comorbidities, and determine the role of PT intervention on these patients. DCD was detected in 55.2% of 96 consecutive children with ADHD (81 males, 15 females), mostly among patients with the inattentive type (64.3% compared with 11% of those with the hyperactive/impulsive type, p<0.05). Mean age was 8 years 4 months (SD 2 y). Individuals with both ADHD and DCD more often had specific learning disabilities (p=0.05) and expressive language deficits (p=0.03) than children with ADHD only. Twenty-eight patients with ADHD and DCD randomly received either intensive group PT (group A, mean age 9 y 3 mo, SD 2 y 3 mo) or no intervention (group B, mean age 9 y 3 mo, SD 2 y 2 mo). PT significantly improved motor performance (assessed by the Movement Assessment Battery for Children; p=0.001). In conclusion, DCD is common in children with ADHD, particularly of the inattentive type. Patients with both ADHD and DCD are more likely to exhibit specific learning disabilities and phonological (pronunciation) deficits. Intensive PT intervention has a marked impact on the motor performance of these children.     

A staged approach for identifying children with developmental coordination disorder from the population

The purpose of this study was to describe the motor, attention and intellectual characteristics of a population-based sample of children first screened for motor impairment and to discuss the recruitment and identification methods employed. A two stage cross-sectional, school-based survey was conducted to screen for children with motor coordination difficulties and to identify children with an existing diagnosis of attention deficit hyperactivity disorder/attention deficit disorder (ADHD/ADD). The identified children, and a random sample of typically developing children, were assessed to confirm or rule out the presence of developmental coordination disorder (DCD).Six thousand four hundred and seventy five children were invited to participate; 2943 children, with parental consent, completed the initial screening process. Two hundred eighty four children with possible motor impairment were identified. The parents of 113 children consented to a full assessment. Sixty eight children of the 113 children met diagnostic criteria for DCD, and 26 also had ADHD. Twenty eight of the 55 children who screened in with a diagnosis of ADHD were subsequently found to have DCD. The total number of children with confirmed characteristics of DCD was reduced after application of DCD diagnostic criteria. This study differs from others with regard to the additional screening for children with ADHD/ADD. The second stage assessment notably increased the number of children identified with both ADHD and DCD.     

Working memory, processing speed, and set-shifting in children with developmental coordination disorder and attention-deficit-hyperactivity disorder

It has been suggested that the high levels of comorbidity between attention-deficit-hyperactivity disorder (ADHD) and developmental coordination disorder (DCD) may be attributed to a common underlying neurocognitive mechanism. This study assessed whether children with DCD and ADHD share deficits on tasks measuring working memory, set-shifting, and processing speed. A total of 195 children aged between 6 years 6 months and 14 years 1 month (mean 10y 4mo [SD 2y 2mo]) were included in this study. A control group (59 males, 79 females), a DCD group (12 males, six females), an ADHD-predominantly inattentive group (16 males, four females), and an ADHD-combined group (15 males, four females), were tested on three executive functioning tasks. Children with DCD were significantly slower on all tasks, supporting past evidence of a timing deficit in these children. With few exceptions, children with ADHD did not perform more poorly than control children. These findings demonstrate the importance of identifying children with motor deficits when examining tasks involving a timing component.     

Tool length influences reach distance estimation via motor imagery in children with developmental coordination disorder

Purpose: Children with developmental coordination disorder (DCD) often have difficulties with planning and generating a precise visuospatial representation of intended actions and using motor imagery to mentally represent motor behavior. Here, we aimed to extend the investigation of motor imagery in children with DCD by exploring its use with an estimation of reach paradigm that combines action representation and extension of space with tools. Method: Two groups of 18 children with DCD and typically developing (TD) matched controls were tested with an estimation of reach paradigm using a 20-cm (Experiment 1) and 40-cm (Experiment 2) tool. Conditions involved estimations via motor imagery with their arm, tool, and a switch-block (SB) involving an abrupt change of space with an “extension” from arm to tool and a “retraction” from tool to arm. Results: No significant group differences were found with the 20-cm tool; however, with the 40-cm implement, children with DCD were significantly less accurate than their TD counterparts. Conclusions: Compared to TD children, those with DCD have more difficulty estimating reach distances using the longer of two tool lengths: 40 cm compared to 20 cm. This finding may be related to differences in quality of motor imagery and in the ability to create an effective internal model for action in this context. Furthermore, our results suggest that tool length may present an additional action processing constraint on children with DCD. Additional studies are necessary to determine other constraints that children with DCD have when integrating tool use with spatial judgments for reach actions, as well as provide rehabilitation insights that involve motor imagery combined with tool use.     

Postural adaptations to a suprapostural memory task among children with and without developmental coordination disorder

Aim The present study investigated the effects of varying the cognitive demands of a memory task (a suprapostural task) while recording postural motion on two groups of children, one diagnosed with developmental coordination disorder (DCD) and an age‐matched group of typically developing children. Method Two groups, each comprising 38 child volunteers (21 males, 17 females) aged 9 to 10 years, participated in the study. Each child performed a digital memory task at two levels of difficulty, low and high. Positional variability (standard deviation of position) of the head and torso were recorded as the biomechanical responses to the variation in task difficulty. Results Both groups significantly reduced postural motion when engaged in the high‐difficulty condition (p<0.05) compared with the low‐difficulty condition. Children with DCD exhibited significantly higher levels of postural motion (p<0.05) than the typically developing children. The typically developing children significantly reduced their postural motion in the high‐difficulty condition (p<0.05) compared with the low‐difficulty condition, whereas children with DCD did not. Interpretation Our results suggest that the postural responses of children with DCD differ from those of typically developing children while engaging in a memory task with various levels of difficulty.     

Covert orienting of visuospatial attention in children with developmental coordination disorder

It is still unclear whether impairments in visuospatial processing in children with developmental coordination disorder (DCD) are a consequence of their motor deficits or are independent of them. In two experiments, 20 children with DCD and 20 matched controls were tested on the covert orienting of a visuospatial attention task (COVAT). Experiment 1 used a COVAT with peripheral cues and an 80% probability that targets would appear at the cued location. While the results suggested a deficit in the disengage operation of orienting covert attention for the DCD group, they were difficult to reconcile with models of covert orienting and the results of past research. Experiment 2 tested subjects on two new versions of the COVAT: the first used peripheral cues and no probability information (exogenous mode), and the second used central cues and an 80% probability that targets would appear at the cued location (endogenous mode). The DCD group displayed attentions orienting deficits only for the endogenous mode. These results suggest that impairments in the endogenous control of visuospatial attention are independent of motor deficits in DCD.     

Attention deficits and clumsiness in Swedish 7-year-old children

A population study of 409 seven-year-old children in a middle-sized Swedish town was performed. All children were examined by the same doctor and evaluated by means of parent interview, motor examinations, and teacher reports on behaviour in the classroom. Follow-up was carried out 8 months later. The rate of severe problems in the fields of attention deficit-hyperactivity disorder (ADHD), developmental coordination disorder (DCD), and deficits in attention, motor control, and perception (DAMP) (the combination of ADHD and DCD) was 6.1%, with boys being affected more frequently than girls. There was considerable overlap between ADHD and DCD, with about half of each diagnostic group also meeting criteria for the other diagnosis. Attention deficits at diagnosis strongly predicted attention deficits at follow-up. If parents had noted attention deficits in the home setting, then teachers almost always independently agreed that there were similar problems in the classroom. However, the reverse did not always apply. Clumsiness also showed striking stability over time. The diagnosis of DAMP, particularly severe DAMP, had a stronger association with classroom dysfunction and with high Conners scores than did diagnoses of ADHD or DCD. It is concluded that DAMP may be a clinically valid diagnostic construct.     

Motor impairments screened by the Movement Assessment Battery for Children-2 are related to the visual-perceptual deficits in children with Developmental Coordination Disorder

This study was to examine to what extent the motor deficits of children with Developmental Coordination Disorder (DCD) verified by the Movement Assessment Battery for Children-2 (MABC-2) are linked to their visual-perceptual abilities. Seventeen children with DCD and seventeen typically developing children (TD) aged 5–10 years screened from a total of 250 children were recruited. The assessments included MABC-2, traditional test of visual perceptual skills (TVPS-R), and computerized test for sequential coupling of eye and hand as well as motion coherence. The results indicated that children with DCD scored lower than TD in MABC-2, and their total scores were highly correlated with manual dexterity component scores. DCD group also showed poor visual-perceptual abilities in various aspects. The visual discrimination and visual sequential memory from the TVPS-R, the sequential coupling of eye and hand, and the motion coherence demonstrated a moderate or strong correlation with the MABC-2 in the DCD rather than the TD group. It was concluded that the motor problems screened by MABC-2 were significantly related to the visual-perceptual deficits of children with DCD. MABC-2 is suggested to be a prescreening tool to identify the visual-perceptual related motor deficits.     

Physical activity and fitness in children with developmental coordination disorder: a systematic review

Developmental coordination disorder (DCD) is a neurodevelopmental condition characterized by poor motor proficiency that interferes with a child's activities of daily living. Activities that most young children engage in such as running, walking, and jumping are important for the proper development of fitness and overall health. However, children with DCD usually find these activities challenging. A systematic review of the literature was conducted to synthesize the recent available data on fitness and physical activity in children with DCD, and to understand the extent of the differences between children with DCD and their typically developing peers. Systematic searches of electronic databases and reference lists identified 40 peer-reviewed studies meeting the inclusion criteria. These studies were reviewed in terms of: (a) study design, (b) population, (c) assessment tools, (d) measures, and (e) fitness and physical activity outcomes. It has been demonstrated that body composition, cardiorespiratory fitness, muscle strength and endurance, anaerobic capacity, power, and physical activity have all been negatively associated, to various degrees, with poor motor proficiency. However, differences in flexibility were not conclusive as the results on this parameter are mixed. Studies’ limitations and the impact of results on future work are discussed.