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M.Sc. (Physiotherapy), Faculty of Haelth Sciences, University of the Witwatersrand, 2008. / Children with Developmental Coordination Disorder (DCD) are a heterogeneous group who have a marked impairment in the performance of functional motor skills. DCD affects 5-8 % of children in the mainstream educational system, with twice as many boys than girls being affected. DCD often co-occurs with other developmental disorders such as Attention Deficit Hyperactivity Disorder (ADHD), Attention Deficit (ADD), severe learning disabilities and reading disabilities and is often associated with educational, social and emotional problems that often persist beyond adolescence. Current research has shown that children with DCD do not outgrow their motor problems and without intervention they do not improve (Zoia et al, 2006; Barnhart et al, 2003; Peters and Wright, 1999). The aim of this study was to investigate the effect of an eight week group gross motor intervention programme on 26 children with Developmental Coordination Disorder (DCD) at Forest Town School, which is a special-needs school for children with learning disabilities. The intervention programme consisted of gross motor activities commonly used by the physiotherapists at the school for their DCD groups. The children attended a thirty-minute physiotherapy session a week, in groups of up to 6, for eight weeks. The children’s motor performance was assessed using the Bruininks-Oseretsky Test for Motor Proficiency (BOTMP) pre- intervention, post- intervention and then eight weeks after the intervention had ceased. The children were used as their own controls. The results of the statistical analysis revealed that the mean group gross motor and fine motor scores significantly improved after the intervention. It was found that the gross motor scores improved by a larger percentage than the fine motor, which may be because the intervention consisted purely of gross motor activities. The fine motor scores also significantly improved, implying that there was a transfer or generalisation of skills to the fine motor tasks. The improvement in the motor performance was found to be maintained eight weeks after the intervention was stopped. It was concluded in the study that the eight week group physiotherapy programme at Forest Town School improved the motor skills of children with DCD and learning difficulties. Physiotherapy in a small group may therefore be a cost effective solution for the treatment of children with DCD in government-funded schools and hospitals that have a limited number of physiotherapists available to treat these children.

For the last 100 years, poor motor coordination in children has been recognized as a developmental problem. As early as 1937, these children were classified as “clumsy.” Since then, other terms such as “motorically awkward,” “motor impaired,” and “physically awkward” have been used to describe these children, and the terms “developmental apraxia” and “perceptual motor difficulties” have been used to characterize this developmental problem. Since the 1994 International Consensus Conference on Children and Clumsiness, the term “developmental coordination disorder” (DCD) has been used to describe the condition of children with motor incoordination.

This study compared the motor performance of children identified with Developmental Coordination Disorder (DCD) with those of a matched group categorised as typically developing (TD). Based on the existing literature, vertical jumping was the task selected as it is a fundamental movement skill (Gallahue & Ozmun, 2002), and a single optimal coordination pattern has been shown to exist (e.g., Bobbert & van Ingen Schenau, 1998).Within the conceptual framework developed for this enquiry, jump height, the performance outcome, was the highest level variable. Level 2 variables described the centre of mass displacement at key instants during the jumping movement. Level 3 variables identified measures of velocity, force and power, which underpin the movement, and level 4 variables described the countermovement specific to this task. This provided a more thorough analysis than previously reported in DCD literature for jumping. The objective of this study was to identify possible mechanisms of DCD in order to advance the understanding of this impairment. A cross-sectional sample (n = 165) of males and females aged between 5 and 12 years was drawn from a school in Victoria, Australia. Using the Movement–Assessment Battery for Children (M-ABC), 62 children from the sample were identified as having DCD with total impairment scores below the 15th percentile for their age-band (Henderson & Sugden, 1992). From the remaining children assessed, who all scored above the 15th percentile, 62 were matched with the DCD group to form the TD group (n= 62). Participants performed three maximal vertical jumps, standing on a single forceplate. Each child’s best vertical jump was analysed using forceplate (700 Hz) and 2D sagittal kinematic data from a single camera video (50 Hz) capture. The results confirmed previous findings that DCD children jump lower than their TD peers, although there was a considerable overlap in motor ability between the groups. Peak VCOM occurred earlier in the jumping movement in the DCD group, when compared to the TD group. This meant a longer elapsed time from the instant of peak VCOM to take-off, which was attributed to coordination error. The earlier occurrence of peak VCOM in the DCD group could be explained by the lower shank angular velocity at take-off. In addition, the DCD group produced lower jump impulse and peak power. Further probing of the jump height data revealed an interesting relationship between age band and jump height that was gender specific. It was noted that for the DCD males, less than 1% of the variance found in jump height could be accounted for by age-band. In contrast, the explained variance for jump height by age-band was 24% for the TD males. The females showed similar relationships for jump height and age-band in both groups. It was thought that this may reflect physical activity avoidance caused by greater social pressures on boys to be good at sports (e.g., Parker & Larkin, 2003).In addition, a further analysis of the DCD group data was undertaken to compare those who had difficulties in dynamic balance and those who did not. In this analysis, body mass was found to have a significant effect on leg stiffness (Kleg), and when accounted for as a covariate, greater Kleg in the DCD group with dynamic balance difficulties was found. A possible explanation is that for the DCD group with dynamic balance difficulties, the transition from joint flexion to extension during the countermovement was problematic, and resulted in excessive muscle co-activation. This study provides some possible directions for further investigations into coordination issues for DCD children. The time elapsed from peak VCOM to take-off and the shank angular velocities at take-off were identified as key indicators of a poorly coordinated jump. High levels of Kleg reflected difficulties in the transition from joint flexion to extension during the countermovement in those DCD children with dynamic balance problems. Based on these key variables and others that differentiated between groups a more parsimonious conceptual framework is presented. For future enquiry, a more holistic approach for the study of children with such impairments is recommended. This includes exploring the environment these children are exposed to in order to gain a more thorough understanding of practice and learning effects. Understanding of differences in motor ability requires an expanded framework to include information on genetic and socio-cultural factors, and their impact upon important psychology, physical fitness, nutrition, body composition and physical activity parameters.

As a pedestrian at the roadside, the two most informative cues as to the distance and rate of closure of a vehicle are its optical size and the rate of expansion of the optical image. In addition, the time to arrival of an approaching vehicle can be perceptually estimated by the ratio of these two variables, referred to as tau (Lee, 1976). Sensitivity to optic expansion is critical for collision avoidance and was measured in populations of adults, typically developing children, and in children with Developmental Coordination Disorder (DCD), an idiopathic condition characterised by marked impairments in motor coordination that negatively impact on activities of daily living. A central tendency was found in adults (n = 193) between 18 to 59 years of age to make significant errors in judging the approach rates of two vehicles. Inflated errors were observed in children (n = 136) between 6 to 17 years of age, with decreased sensitivity in the youngest age group (6 to 11 years). Furthermore, a significant decrement was found in children (n = 9) with DCD between 6 to 11 years of age. Across all groups, a systematic vehicle size bias was found, whereby faster small vehicles were perceived as travelling slower than larger vehicles. This pattern of results suggest that in general, observers are not utilising tau in judgments of relative approach rates for speeds typically encountered at the roadside, but instead rely on optical expansion that does not compensate for image size. Errors due to a reliance on optic size were inflated in children with DCD, potentially placing them at significantly greater risk at the roadside. To examine the decreased sensitivity observed in DCD, thresholds for detecting visual looming were measured in children (n = 11) with DCD between 6 to 11 years of age. A significant deficit was found when vehicles were presented in perifoveal vision, whereby children with DCD may perceive vehicles that are 5 seconds away as stationary if they are travelling any faster than ~14 mph. This demonstration of a low-level visual processing deficit could suggest an immaturity in the dorsal stream network and explain some of the difficulties that characterise DCD. Critically, perceptual judgments at the roadside are inextricably linked to the motoric capability of the observer. If a pedestrians crossing time is greater than the time available, collision will occur. Crossing gap thresholds were measured and compared to walking times for a single vehicle approaching at varying speeds. Children (n = 9) with DCD between 6 to 11 years of age left considerably longer temporal crossing gaps than their action capabilities necessitated. However, when children with DCD were presented with multiple vehicles in a virtual reality environment, they accepted crossing gaps at all approach speeds that were shorter than the time it would take them to cross. This suggests that children with DCD may not have the perceptual accuracy to predict their required action gaps in a road crossing situation. One explanation for these findings could be a difference in DCD in how vision is dynamically allocated to facilitate the preparation of goal-directed actions. Dynamic allocation of visual attention was assessed in a series of experiments that measured eye movement latencies and hand movement accuracy in children (n = 5) with DCD between 6 to 11 years of age. Both measures were found to be comparable in DCD with their typically developing peers regardless of task complexity, indicating that the allocation of visual attention is not deficient in children with DCD. The prospective control of movement in our everyday lives is critically depended on estimating the immediacy of approaching objects. Combined, these results indicate that children with DCD may be particularly vulnerable at the roadside due to a visual motion processing deficit, consistent with atypical function across broad neural structures such as the dorsal stream.

Esse trabalho tem como foco a condição mencionada acima, nomeada como Transtorno do Desenvolvimento da Coordenação (TDC) pela AMERICAN PSYCHIATRIC ASSOCIATION DSM IV (2002) e Transtorno específico do desenvolvimento motor, pela ORGANIZAÇÃO MUNDIAL DA SAÚDE - CID-10 (1993). Foi discutido que a base da classificação usada nas pesquisas acerca desse transtorno tem como finalidade primária o diagnóstico clínico, e também apontado as conseqüências desse tipo de definição para orientação de pesquisas. A heterogeneidade das amostras de TDC utilizadas em pesquisas prévias pode ser vista como um obstáculo à própria investigação do fenômeno. Foi explorada uma possibilidade de superar esse problema através de uma abordagem diferencial, na qual se buscou diferença na capacidade de organização temporal do movimento (timing) dentro da própria população que sofre desse transtorno, na tentativa de caracterizar grupos com maior homogeneidade. Para isso 44 sujeitos, entre 9 e 11 anos, foram selecionados com base no seu desempenho do teste MABC (HENDERSON & SUGDEN, 1992), sendo 20 sujeitos com TDC e 24 normais. Esses sujeitos foram submetidos a uma bateria de tarefas de timing para caracterizá-los. As variáveis foram analisadas conjuntamente através de uma análise de clusters. O exame do coeficiente de fusão e observação do dendograma sugeriu a partição em dois clusters. Os resultados mostraram que os sujeitos uma dos clusters podem ser caracterizados com relação apenas ao timing sincronizório. As demais variáveis de timing não discriminam os dois subgrupos / The focus of this study was the condition above mentioned, named Developmental Coordination Disorder (DCD) by the AMERICAN PSYCHIATRIC ASSOCIANTION DSM IV (2002) and by WORLD HEALTH ORGANIZATION CID - 10 (1993). It was discussed that the purpose of the classification DSM IV and CID 10 is to guide the clinical diagnostic, and pointed out the implications of this criteria to orient how to select subjects in the researches. The heterogeneity of the DCD samples used in previous researches can be seen as a hindrance to investigating the problem itself. To try to overcome that obstacle, a differential approach was used, in which the difference in timing within the population who suffers that disorder was searched for, in order to characterize more homogenous groups. We selected 44 children, ranging from 9 to 11 years old, based on their performance in the MABC test (HENDERSON & SUGDEN, 1992), being 20 children with DCD and 24 without it (normal). The variables are analyzed together through a clusters analyzes. Examination of the fusion coefficients and the cluster dendogram suggested two groups. The results suggested that the DCD subjects who were grouped in each of the clusters can be characterized by their performance in the synchronic timing tasks only. The other timing variables do not discriminate the two subgroups

Esse trabalho tem como foco a condição mencionada acima, nomeada como Transtorno do Desenvolvimento da Coordenação (TDC) pela AMERICAN PSYCHIATRIC ASSOCIATION DSM IV (2002) e Transtorno específico do desenvolvimento motor, pela ORGANIZAÇÃO MUNDIAL DA SAÚDE - CID-10 (1993). Foi discutido que a base da classificação usada nas pesquisas acerca desse transtorno tem como finalidade primária o diagnóstico clínico, e também apontado as conseqüências desse tipo de definição para orientação de pesquisas. A heterogeneidade das amostras de TDC utilizadas em pesquisas prévias pode ser vista como um obstáculo à própria investigação do fenômeno. Foi explorada uma possibilidade de superar esse problema através de uma abordagem diferencial, na qual se buscou diferença na capacidade de organização temporal do movimento (timing) dentro da própria população que sofre desse transtorno, na tentativa de caracterizar grupos com maior homogeneidade. Para isso 44 sujeitos, entre 9 e 11 anos, foram selecionados com base no seu desempenho do teste MABC (HENDERSON & SUGDEN, 1992), sendo 20 sujeitos com TDC e 24 normais. Esses sujeitos foram submetidos a uma bateria de tarefas de timing para caracterizá-los. As variáveis foram analisadas conjuntamente através de uma análise de clusters. O exame do coeficiente de fusão e observação do dendograma sugeriu a partição em dois clusters. Os resultados mostraram que os sujeitos uma dos clusters podem ser caracterizados com relação apenas ao timing sincronizório. As demais variáveis de timing não discriminam os dois subgrupos / The focus of this study was the condition above mentioned, named Developmental Coordination Disorder (DCD) by the AMERICAN PSYCHIATRIC ASSOCIANTION DSM IV (2002) and by WORLD HEALTH ORGANIZATION CID - 10 (1993). It was discussed that the purpose of the classification DSM IV and CID 10 is to guide the clinical diagnostic, and pointed out the implications of this criteria to orient how to select subjects in the researches. The heterogeneity of the DCD samples used in previous researches can be seen as a hindrance to investigating the problem itself. To try to overcome that obstacle, a differential approach was used, in which the difference in timing within the population who suffers that disorder was searched for, in order to characterize more homogenous groups. We selected 44 children, ranging from 9 to 11 years old, based on their performance in the MABC test (HENDERSON & SUGDEN, 1992), being 20 children with DCD and 24 without it (normal). The variables are analyzed together through a clusters analyzes. Examination of the fusion coefficients and the cluster dendogram suggested two groups. The results suggested that the DCD subjects who were grouped in each of the clusters can be characterized by their performance in the synchronic timing tasks only. The other timing variables do not discriminate the two subgroups

Developmental Coordination Disorder (DCD) is characterised by impairments to motor control and learning, the cause of which remains unclear. Recently, researchers have used cognitive neuroscientific approaches to explore the basis of poor coordination in children, with one hypothesis suggesting that an internal modelling deficit (IMD) is one of the underlying causes of DCD. The aim of this thesis was to further test the IMD hypothesis using a motor imagery paradigm - the mental rotation of hands. Versions of this task were used in all studies to assess motor imagery ability, with an additional whole-body task used in Studies 2 and 3. Further, an alphanumeric rotation task was used in Studies 1 and 2 to assess visual imagery ability. Studies 1 and 2 provided varying levels of support for the IMD hypothesis. In Study 1, only a subgroup of DCD children performed differently from other children in the study on the hand tasks, but tighter task constraints in Study 2 led to overall group differences between DCD and controls in terms of accuracy. The DCD group were also significantly less accurate than controls in the whole-body task, but there were no group differences in either Study 1 or 2 on the visual imagery task. Interestingly, in Study 2, there was an indication that children with severe levels of motor impairment were less accurate than children with less severe motor impairment, suggesting that motor impairment level could play a role in the severity of motor imagery deficits. Study 3 was designed to explore the impact of motor impairment severity on motor imagery ability further. The results confirmed that children with severe DCD had greater motor imagery impairment than children with mild DCD - children with severe DCD performed less accurately than both controls and those with mild DCD in the hand task with instructions and the controls in the whole-body task. Further, those children with mild DCD were able to respond somewhat to motor imagery instructions, whereas those with severe DCD were not. This study provided support to the IMD hypothesis, though the deficit was shown to be dependent on a number of factors. Chapter 5 presents a reasoned account of these various findings and their implications are discussed. It is concluded that motor imagery deficits are evident in many children with DCD, but more so in children with severe motor impairment. A general imagery deficit was ruled out based on the findings of Studies 1 and 2 which showed that visual imagery processes appear intact in children with DCD. Taken together with previous imagery and IMD studies, and related research on feedforward control in DCD, it is concluded that the deficits in motor imagery observed in this thesis are consistent with the hypothesis that an IMD is one likely causal factor in the disorder, particularly in more severe DCD. The observation of differing response patterns between children with mild and severe forms of DCD has important implications for developing a theory of DCD and for remediation.

The purpose of this study was to examine the incidence of obesity and Developmental Coordination Disorder (DCD) of girls in the age group 10-12 years of different race groups in the North-West Province. A second purpose was to determine if DCD status can be predicted effectively among 10-12 year old girls with regard to race, age, percentage body fat, body mass, length, body mass index and bent aim hang. Obesity is the cause of health risks, psychological consequences and improper development (Chantell et al., 1994:116; Marshall & Bouffard, 1994:1997; Treuth et al., 1997:1738). Children with DCD have poor motor abilities and experience problems regarding concentration and social abilities, all of which are necessary for successful schooling (Geuze & Borger, 1993:14; Piek & Edwards, 1997:55; Sugden & Chambers, 1998:139) According to research, the incidence of obesity among children has doubled over the last 20 years, and 10-30% of all children and adolescents can be classified as obese. Causes of obesity may be genetic but a lack of physical activity and an unbalanced diet can also contribute to obesity. Health risks, psycho-social risks and developmental disorders are all indicated in the literature to be consequences of obesity. The incidence of DCD is documented in the literature to be between 5% and 16%. It is also shown that it may be the cause of problems in daily living and at school, and some racial differences with regard to motor differences are indicated. It is also indicated that overweight and obese children are less mobile and that their motor achievement is poorer in movements where the shifting of body weight is required. All the subjects for this study (N=346) completed the Movement ABC (MABC) (Henderson & Sugden, 1992) to determine their DCD status. Fat percentage was determined from the subscapular and triceps skin folds according to the formula of Boileau et al. (1985:17-27), while a body mass index (BMI) (l/w2)above the 85th percentile was used as a criterion for overweight, and a BMI of above the 95th percentile for obesity. The Statistics for Windows computer package was used to determine descriptive statistics and significant differences between the groups. The results showed that the incidence of obesity and DCD were 4,93% and 59,78% respectively. 50% of the white girls, 72,73% of blacks, 0% of coloureds and 100% of Indian girls in the total group who were classified as DCD were also obese. The results indicated a higher relationship between obesity and DCD among the Indian and black girls compared to the white and coloured girls in the DCD group. Indian girls showed the highest incidence of obesity and coloured girls the least. The Indian and black girls also showed the highest incidence of DCD, while the percentages of DCD among all the race groups were higher than the levels indicated in the literature. The percentage of obesity found in the study was lower than in the literature, but higher percentages were found among the Indian and white girls, while all the obese Indian girls were also classified as suffering from DCD. With regard to the second aim of the study, no significant predictors for DCD could be found among the different body composition variables of bent arm hang, race and age, although some tendencies emerged. Results showed that the percentage fat was not a good predictor of DCD status in the group, but in the different racial groups its predictive value became higher. However, none of the variables could be considered good predictors of DCD status among girls, although it can be concluded that there are tendencies towards a relationship between obesity, DCD and race. Thus it is important for children with DCD and obesity (separate and in combination) to be identified and treated with intervention programs as early as possible, and it is essential to include physical activities as part of the treatment (Dussart, 1994:81; LeMure et al., 2000:336). The results of the study indicated that it is important to analyse the needs and characteristics of the different race groups in order to ensure the success of such programs. Indian girls especially should be encouraged to participate in physical activity programmes because of the high percentages of obesity found in the DCD group. / Thesis (M.Sc. (Human Movement Science))--North-West University, Potchefstroom Campus, 2004.

The purpose of this study was to examine the incidence of obesity and Developmental Coordination Disorder (DCD) of girls in the age group 10-12 years of different race groups in the North-West Province. A second purpose was to determine if DCD status can be predicted effectively among 10-12 year old girls with regard to race, age, percentage body fat, body mass, length, body mass index and bent aim hang. Obesity is the cause of health risks, psychological consequences and improper development (Chantell et al., 1994:116; Marshall & Bouffard, 1994:1997; Treuth et al., 1997:1738). Children with DCD have poor motor abilities and experience problems regarding concentration and social abilities, all of which are necessary for successful schooling (Geuze & Borger, 1993:14; Piek & Edwards, 1997:55; Sugden & Chambers, 1998:139) According to research, the incidence of obesity among children has doubled over the last 20 years, and 10-30% of all children and adolescents can be classified as obese. Causes of obesity may be genetic but a lack of physical activity and an unbalanced diet can also contribute to obesity. Health risks, psycho-social risks and developmental disorders are all indicated in the literature to be consequences of obesity. The incidence of DCD is documented in the literature to be between 5% and 16%. It is also shown that it may be the cause of problems in daily living and at school, and some racial differences with regard to motor differences are indicated. It is also indicated that overweight and obese children are less mobile and that their motor achievement is poorer in movements where the shifting of body weight is required. All the subjects for this study (N=346) completed the Movement ABC (MABC) (Henderson & Sugden, 1992) to determine their DCD status. Fat percentage was determined from the subscapular and triceps skin folds according to the formula of Boileau et al. (1985:17-27), while a body mass index (BMI) (l/w2)above the 85th percentile was used as a criterion for overweight, and a BMI of above the 95th percentile for obesity. The Statistics for Windows computer package was used to determine descriptive statistics and significant differences between the groups. The results showed that the incidence of obesity and DCD were 4,93% and 59,78% respectively. 50% of the white girls, 72,73% of blacks, 0% of coloureds and 100% of Indian girls in the total group who were classified as DCD were also obese. The results indicated a higher relationship between obesity and DCD among the Indian and black girls compared to the white and coloured girls in the DCD group. Indian girls showed the highest incidence of obesity and coloured girls the least. The Indian and black girls also showed the highest incidence of DCD, while the percentages of DCD among all the race groups were higher than the levels indicated in the literature. The percentage of obesity found in the study was lower than in the literature, but higher percentages were found among the Indian and white girls, while all the obese Indian girls were also classified as suffering from DCD. With regard to the second aim of the study, no significant predictors for DCD could be found among the different body composition variables of bent arm hang, race and age, although some tendencies emerged. Results showed that the percentage fat was not a good predictor of DCD status in the group, but in the different racial groups its predictive value became higher. However, none of the variables could be considered good predictors of DCD status among girls, although it can be concluded that there are tendencies towards a relationship between obesity, DCD and race. Thus it is important for children with DCD and obesity (separate and in combination) to be identified and treated with intervention programs as early as possible, and it is essential to include physical activities as part of the treatment (Dussart, 1994:81; LeMure et al., 2000:336). The results of the study indicated that it is important to analyse the needs and characteristics of the different race groups in order to ensure the success of such programs. Indian girls especially should be encouraged to participate in physical activity programmes because of the high percentages of obesity found in the DCD group. / Thesis (M.Sc. (Human Movement Science))--North-West University, Potchefstroom Campus, 2004.