Article Spatial Accuracy and Variability in Dart Throwing in Children with Developmental Coordination Disorder and the Relationship with Ball Skill Items Faiçal Farhat 1, Achraf Ammar 2,3,4,5,* , Nourhen Mezghani 6, Mohamed Moncef Kammoun 1,2, Khaled Trabelsi 1,2 , Haitham Jahrami 7 , Adnene Gharbi 2,8 , Lassad Sallemi 1,2, Haithem Rebai 2,9, Wassim Moalla 1,2 and Bouwien Smits-Engelsman 10,11 1 Research Laboratory: Education, Motricity, Sport and Health, EM2S, LR19JS01, High Institute of Sport and Physical Education of Sfax, University of Sfax, Sfax 3000, Tunisia; faical.farhat@isseps.usf.tn (F.F.); moncef.kammoun@isseps.usf.tn (M.M.K.); khaled.trabelsi@isseps.usf.tn (K.T.); lassadsallemi@gmail.com (L.S.); wassim.moalla@isseps.usf.tn (W.M.) 2 High Institute of Sport and Physical Education of Sfax, University of Sfax, Sfax 3000, Tunisia; adnenegharbi@yahoo.fr (A.G.); haithem.rebai@isseps.usf.tn (H.R.) 3 Department of Training and Movement Science, Institute of Sport Science, Johannes-Gutenberg-University Mainz, 55122 Mainz, Germany 4 Research Laboratory, Molecular Bases of Human Pathology, LR19ES13, Faculty of Medicine of Sfax, University of Sfax, Sfax 3000, Tunisia 5 Interdisciplinary Laboratory in Neurosciences, Physiology and Psychology: Physical Activity, Health and Learning (LINP2), UFR STAPS, UPL, Paris Nanterre University, 92000 Nanterre, France 6 Department of Sport Sciences, College of Education, Taif University, Taif 21974, Saudi Arabia; nsmezghanni@tu.edu.sa 7 College of Medicine and Medical Science, Arabian Gulf University, Manama 293, Bahrain; hjahrami@health.gov.bh 8 Physical Activity, Sport and Health Research Unit, National Observatory of Sport, Tunis 1003, Tunisia 9 Citation: Farhat, F.; Ammar, A.; Sports Performance Optimization Research Laboratory (LR09SEP01), National Center for Sports Medicine Mezghani, N.; Kammoun, M.M.; and Science (CNMSS), Tunis 1003, Tunisia 10 Physical Activity, Sport and Recreation, Faculty Health Sciences, North-West University, Trabelsi, K.; Jahrami, H.; Gharbi, A.; Potchefstroom 2520, South Africa; bouwiensmits@hotmail.com Sallemi, L.; Rebai, H.; Moalla, W.; et al. 11 Department of Health and Rehabilitation Sciences, University of Cape Town, Cape Town 7925, South Africa Spatial Accuracy and Variability in * Correspondence: acammar@uni-mainz.de Dart Throwing in Children with Developmental Coordination Abstract: The present study aimed to examine precision and variability in dart throwing performance Disorder and the Relationship with and the relationships between these outcomes and bouncing, throwing and catching tasks in children Ball Skill Items. Eur. J. Investig. Health Psychol. Educ. 2024, 14, 1028–1043. with and without DCD. Children between the ages of 8 and 10 years (n = 165) were classified https://doi.org/10.3390/ according to results obtained on the Movement Assessment Battery for Children (MABC-2) and ejihpe14040067 divided into three groups: 65 children with severe DCD (s-DCD), 45 with moderate DCD (m-DCD) and 55 typically developing children (TD). All children performed the dart throwing test and the Academic Editor: Francisco ball skill items of the Performance and Fitness Test (PERF-FIT). The accuracy and variability of dart Manuel Morales Rodríguez throwing tasks were significantly different between TD and s-DCD (p < 0.01), and also between Received: 2 February 2024 m-DCD and s-DCD (p < 0.01). Participants with s-DCD were also found to perform significantly Revised: 26 March 2024 worse on all PERF-FIT ball skill items than m-DCD (p < 0.001), and m-DCD were significantly poorer Accepted: 9 April 2024 than TD (p < 0.001). The dart score and coefficient of variation of the long-distance task appear to be Published: 16 April 2024 significant predictors for the ball skills and explain between 24 to 29% of their variance. In conclusion, poor results in aiming tasks using darts in children with DCD corroborate with the explanation of deficits in predictive control since the tasks require ballistic movements. Copyright: © 2024 by the authors. Licensee MDPI, Basel, Switzerland. Keywords: children; developmental coordination disorder; motor skill-related fitness; ball skills; This article is an open access article dart throw; task difficulty distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Eur. J. Investig. Health Psychol. Educ. 2024, 14, 1028–1043. https://doi.org/10.3390/ejihpe14040067 https://www.mdpi.com/journal/ejihpe Eur. J. Investig. Health Psychol. Educ. 2024, 14 1029 1. Introduction Children with developmental coordination disorder (DCD) exhibit slow, effortful, imprecise, and ill-coordinated movements and are more depended on visual information [1]. The leading hypothesis that best explains motor coordination and skill learning deficits is that children with DCD have difficulties with predictive motor control [2]. In this context, studies examining predictive motor control, such as adaptations in grip force, anticipatory postural adjustments, and predictive control of eye movements, have shown that motor outcome prediction is impaired in children with DCD [2]. In addition to children with DCD having less accurate, slower, and more variable motor performance [3], they also have difficulties visually tracking moving objects [4], which is particularly important in active playground games using balls, such as catching a ball or aiming [2]. The deficits in predictive control in children with DCD can manifest as problems with fine and gross motor skills such as throwing and catching a ball, a set of skills that children with DCD have considerable difficulty with [5]. Proficient ball skills are essential because playground games and physical education classes often include aiming, throwing and catching activities [6]. Indeed, problems with coordination in children with DCD often restrict them from executing functional skills, which are needed for effective participation in sports and leisure activities [7,8]. These difficulties with motor control during ball catching lead to a large number of aiming and catching errors [9]. Motor control theories state that when an action is planned, the motor parameters related to that action such as the trajectory, speed, and required precision are represented as an internal model [10]. Internal models contribute to efficient, accurate and smooth motor performance, limiting the requirement for the motor system to depend on slower varieties of feedback-based control to correct the movement [11]. This ability permits children to anticipate movement results, determine the required control functions and achieve desired outcomes such as distance, timing and force [12]. Children with DCD have a limited ability to utilize internal models for motor control [13]. Jucaite et al. [14] reported that postural and manual forces could not be scaled in either the temporal or amplitude domains in children with DCD. Their study demonstrated that children with DCD modified their grip forces but exhibited temporal delays in the corresponding postural adaptations. Impaired force control was shown to be related to timing [15] and fine-tuning of the force [16]. In this context, Smits-Engelsman et al. [17] also showed that children with DCD produced more variable force trajectories than controls did. In clinical practice, ball skills are typically measured using tests such as M-ABC [18] and BOT [19]. Standardized tests assess ball skills in a very predictable context, which makes the tests reliable but more distant from real-world ball games where trajectory prediction is one of the determining factors [20]. The spatial and temporal accuracy of the movement patterns are crucial because the hands (thus the body) must catch and throw the ball at the right time and place, or release a ball or dart with the right precision. This requires motor control, which refers to an adaptive process of the variables given the motor pattern, such as force, speed, and timing [4]. The recently developed Performance and Fitness test (PERF-FIT) contains repetitive bouncing and catching, throwing and catching items, where children can move freely around and adapt their body position when needed based on available feedback [21]. A task in which fine-tuning of a skilled open-loop-controlled motor action can be tested is throwing darts. For throwing movements including darts, control is related to both the target distance and mass of the object manipulated. Likewise, in the current study, dart throwing requires more end point precision than bouncing and catching, throwing and catching, or a throw for distance (explosive power). On the other hand, less precise executed bouncing or throwing movements could still be corrected for if hand and body movements are adapted fast enough to the throwing error so the ball can still be caught, while error correction is not possible once the dart has been released from the hand. Hence, these tasks have both similarities and differences from a motor control perspective. Eur. J. Investig. Health Psychol. Educ. 2024, 14 1030 Many aspects of motor control and executive function determine the success of an aiming movement. Darts are thrown overarm, with forward movement of the arm, mainly elbow extension, but this also requires an adequate throwing position. The adjustment of the movement properties (direction and velocity) and the temporal accuracy of the grip opening during the hand’s forward movement to release the dart will regulate where it lands. Moreover, these parameters need to be adapted with respect to the external frame of reference defined by the target board. Hence, dart throws include, in addition to the ability to process information to create the right movement pattern, the ability to grade forces with extreme precision [22]. Thus, when throwing a dart or a ball, the online configuration of several joints (i.e., shoulder, elbow, and wrist) must be monitored during the movement to identify when the arm is in the right position to release the object. In the present study, we investigated dart throwing as a typical example of an open- loop (ballistic) aiming task, hence requiring predictive control. Predictive control is based on prior knowledge of the dynamics of moving arms and the internal disturbances caused by arm movements upon the body. The anticipated variables (such as force, timing, and changes in visual input) are based on acquired associations between output signals and their effects on effectors during repeated practice or experience [23]. Based on this knowledge, the central nervous system can correctly program anticipatory postural adaptations [24]. Most studies comparing movement accuracy in children with DCD have used tasks where visual correction during movement execution is possible. For instance, it has been found that when children with DCD move toward a target in visually guided aiming movements, they make considerable endpoint errors and have less fluent movement profiles than their well-coordinated peers [16]. Importantly, in these visually guided aiming movements, children may choose to move more slowly to be more accurate, which is not an option in dart throwing. However, vision still plays an important role in a dart throw task. To hit a specified target with a dart, movement parameters, which are determined in a body-related frame of reference, must be calibrated relative to an external frame of reference. Generally, vision establishes the link between these various points of reference [25]. To our knowledge, no empirical study has investigated the differences between chil- dren with DCD and TD children in terms of throwing darts and ball skills. In these skills, children must manipulate different objects (darts and balls) with different strategies under various motor control conditions. Therefore, the purpose of the present study was to examine the precision and variability of dart-throwing performance and the relationships between these outcomes and ball skills, which have aiming and catching components, in children with and without DCD. Based on previous studies, we hypothesized that, compared with TD children, chil- dren with DCD would be less accurate (as measured by the dart score) and have greater variability (as measured by the coefficient of variation or CV) in performing a dart task. We also expected that this difference would be greater in the more difficult version of the task (standing further away from the target) and greater in the severe DCD group than in the moderate DCD group and TD children. Moreover, moderate correlations are expected between the dart outcomes and the ball skill-related activities of the PERF-FIT because they only partly share a common underlying construct (aiming or throwing at a target) and control modes (predictive versus online control). 2. Materials and Methods 2.1. Procedure The protocol and study design were approved by the Ethical Committee of the Uni- versity Hospital of Sfax, Tunisia (CPP SUD N◦ 0301/2021). Children were tested at their schools. After a full explanation of the procedure and prior to testing, all the parents provided written consent and signed child assent forms. Twelve assessors received 10 h training on all the outcome measures. Children’s length and weight were measured before testing. All tests were administered at a maximum of one week apart. Administration of the MABC-2 took approximately 25–35 min. The PERF-FIT required approximately 25–45 min. Eur. J. Investig. Health Psychol. Educ. 2024, 14 1031 The dart throwing test took 15–25 min. Before scoring, each test item was explained to the child, demonstrated, and practiced according to the manuals. 2.2. Participants To select the participants, teachers and parents were asked to identify children with motor coordination problems based on their observations on the playground, in class or at home. Children with DCD were classified using the four DSM-5 criteria [26]. All the chil- dren aged 7 to 10 years with an MABC-2 score at or below the 16th percentile (Criterion A); identified by a parent or teacher as having a motor coordination impairment (Criterion B); whose parents noted difficulty throughout the early developmental period (Criterion C); where no medical condition or comorbidity known to interfere with motor abilities was noted; and whose teacher confirmed the absence of intellectual or cognitive disability (Criterion D) appeared to meet the DCD criteria. Through this procedure, 110 children with DCD were selected to participate in this study. These children were age- and sex-matched at a 2:1 ratio, with 55 TD children from the same grade. TD children were recruited from the same classes in the school as the children with DCD were. No additional developmental conditions such as attention deficit hyperactivity disorder, dyslexia, or autism spectrum disorder were reported in any of the groups. The inclusion criteria for the TD children were as follows: (1) no evidence of functional motor problems as observed by their teacher or parent, (2) a score above the 16th percentile on the MABC-2, (3) no diagnosis of a significant medical condition as reported by a parent and (4) the absence of intellectual or cognitive impairment as confirmed by their teacher. Based on their MABC-2 scores, the children with DCD were divided into moderate DCD (n = 45) and severe DCD (n = 65) groups to examine the impact of DCD on the severity of motor deficiencies. 2.3. The Movement Assessment Battery for Children-2 (MABC-2) All the children completed the MABC-2 age band 2 (7- to 10-year-old children). The MABC-2 test was used to measure motor coordination [18] and to confirm DSM-5 Criterion A for DCD. The MABC-2 test consists of eight items that are evaluated on three different com- ponents: manual dexterity, aiming and catching, and balance. A percentile score of five or less indicates severe motor problems (we will refer to this group as severe DCD or s-DCD), while a score between 9 and 16 suggests that the child is at risk of having movement difficul- ties (we will refer to this group as moderate DCD or m-DCD), and a score > 16th percentile indicates normal motor performance. The MABC-2 test has demonstrated good validity and test–retest reliability, with ICC values ranging from 0.92 to 0.98 [26]. 2.4. Performance and Fitness Test (PERF-FIT) The PERF-FIT is a functional measure of motor skill-related fitness in children [27]. The PERF-FIT is the first standardized test to establish norms for African children and is an affordable testing tool for low-resource areas. The test is suitable for this age group (elementary school children). The items of the PERF-FIT were designed to be used through- out the full age range. The PERF-FIT has good structural and ecological validity, excellent content validity, and good reliability [28,29]. The PERF-FIT consists of two subscales. The power and agility subscale comprise three agility items (running, stepping, and side jumping) and two explosive power items (overhead throw and standing long jump). The motor skills performance subscale contains five series of tasks with increasing difficulty: (1) bounce and catch ball (2), throw and catch ball, (3) static balance and dynamic balance, (4) jumping, and (5) hopping. For this study, only the ball skills items and the explosive power overhead throw were used because of their expected relationship with the dart task and M-ABC. In an earlier study, throwing and bouncing item series of the PERP-FIT were low to moderately related to the MABC-2 aiming and catching score [21]. Eur. J. Investig. Health Psychol. Educ. 2024, 14 1032 2.5. Dart-Throwing Test The dart throwing test started after the initial training period. This training period included 15 darts thrown in five blocks of three from two distances (2.37 and 3.56 m) [30]. The task was to throw the darts as close to the bullseye as possible. The two distances were marked by a line on the floor. The test runs consisted of six throws at each of the two distances, in a randomized order; the height of the official dartboard was placed on a wall so that its center was at eye level for each child. The children were required to maintain the same throwing technique in both conditions. Score Calculations The throw was scored depending on its position on the board (0–10). A dart that missed or bounced off the board received a score of zero. The target consisted of a series of 10 concentric rings. Two outcomes were used to measure the accuracy and consistency [31]. The first was the mean score of the six throws. This score can range from zero (all misses) to ten (all bullseye); it can be considered a measure of accuracy, with a high score indicating high accuracy. The second measure of performance was the coefficients of variation (CV) of the score: SD score/mean score, a lower coefficient indicating a higher consistency. 2.6. Statistical Procedure All variables were examined to determine whether the distributions were normal or skewed. No outliers were present in the data. ANOVA was used to test for differences in demographic variables among the three groups. The chi2 test was used to determine the sex distribution across groups. Repeated measures ANOVA were used to examine the effect of tasks (within subject: short and long distance) and group (between subject: TD, m-DCD, s-DCD) and possible interactions. One-way ANOVA was used to examine differences between the three groups on the PERF-FIT measures. A post hoc test with Bonferroni correction was used if main effects for group or interactions were found. The magnitude of the differences per group was determined using Cohen’s d-values of 0.5 (moderate effect size) and 0.8 (large effect size) [32]. To test for task specificity of throwing skills, Pearson’s correlations were calculated to assess the relationships between MABC-2 aiming and catching scores, PERF-FIT ball skill items (raw scores) and dart throw performance. A stepwise multiple regression analysis was used to determine the best set of predictor variables (dart outcomes) for the ball skill items. The significance level was set at p < 0.05. All the statistical analyses were conducted using the Statistical Package for the Social Sciences software (SPSS, version 28.0; SPSS, Inc., Chicago, IL, USA). 3. Results 3.1. Participants The anthropometric data of the two DCD groups and the control group are shown in Table 1. Significant differences in weight and body mass index were found between groups (p < 0.001). Post hoc tests showed that the TD group was different from the DCD group, but the m-DCD and s-DCD groups were not different in weight or BMI. There were no significant group differences in age or height (p > 0.05). Differences in the total and subscale scores on the MABC 2 between the groups are also shown in Table 1. The sex distributions of the three groups were comparable (Chi2 1.19, p = 0.55) (Table 2). Table 1. Demographic and background information of the three groups (TD, m-DCD and s-DCD). s-DCD (n = 65) m-DCD (n = 45) TD (n = 55) Statistics Mean SD Mean SD Mean SD F-Value p-Value Age (years) 9.05 0.82 8.93 0.86 9.07 0.84 0.38 0.68 Height (m) 1.38 0.06 1.38 0.06 1.39 0.07 1.27 0.28 Eur. J. Investig. Health Psychol. Educ. 2024, 14 1033 Table 1. Cont. s-DCD (n = 65) m-DCD (n = 45) TD (n = 55) Statistics Mean SD Mean SD Mean SD F-Value p-Value Weight (kg) 38.3 4.47 34.3 4.93 31.8 4.54 30.45 <0.001 BMI (kg m2) 20.03 1.18 17.62 2.95 16.25 1.25 30.96 <0.001 Total Standard Scores 3.7 0.8 6.4 0.5 9.60 1.1 711.35 <0.001 Manual Dexterity 5.0 1.2 7.4 0.9 9.4 1.0 265.19 <0.001 Aiming and Catching 5.1 1.3 7.2 0.9 10.1 1.4 252.52 <0.001 Balance 4.8 0.9 7.1 0.9 9.5 1.2 58.41 <0.001 SD = standard deviation, TD = typically developing, m-DCD = moderate DCD, s-DCD = severe DCD. Table 2. Gender distribution over groups (no significant differences). Group n % Boys % Girls TD 55 49.1 50.9 m-DCD 45 57.8 42.2 s-DCD 65 47.7 52.3 Total 165 50.9 49.1 TD = typically developing, m-DCD = moderate DCD, s-DCD = severe DCD. 3.2. Dart Throw Measurements Dart Scores: Table 3 reports the means and standard deviations for the TD and the DCD groups on dart scores and effect sizes. Table 3. Means (M) ± standard deviations (SD) for the dart scores and effect sizes for the total differences (eta squared) between the 3 groups and pair-wise comparison (Cohen’s d). s-DCD (n = 65) m-DCD (n = 45) TD (n = 55) 3 Groups TD/m-DCD TD/s-DCD m-DCD/s-DCD Mean SD Mean SD Mean SD Eta Squared Cohen’s d Cohen’s d Cohen’s d Dart Score Short 2.87 0.39 3.70 0.63 4.15 0.79 0.45 0.62 2.11 1.64 Dart Score Long 2.30 0.38 3.36 0.45 3.49 0.59 0.58 0.25 2.44 2.58 SD = standard deviation, TD = typically developing, m-DCD = moderate DCD, s-DCD = severe DCD. A repeated measures ANOVA revealed a significant main effect of group for dart scores (F(2, 162) = 95.29, p < 0.001; Figure 1). Additionally, a large main effect of task was found, showing that the 50% greater distance led to darts landing less close to the target (F 1,162 = 275.91, p < 0.001). Importantly, the statistical analysis revealed a significant interaction effect between group and task for dart score (F (2, 162) = 8.05, p < 0.001). Indicating that the groups responded differently in the task conditions. Post hoc analysis revealed that for the short-distance comparisons, dart score was significantly different between the TD- and m-DCD, TD and s-DCD, and m-DCD and s-DCD (all p ≤ 0.001). However, for long distance, the dart score was not different between the TD and m-DCD groups (p = 0.52) but only for the comparisons between TD and s-DCD (p < 0.001), and m-DCD and s-DCD (p < 0.001). Coefficient of variation: Table 4 reports the means and standard deviations for the TD and the DCD groups on CV and effect sizes. A repeated measures ANOVA revealed a significant main effect of group for variability (F (2, 162) = 56.18, p < 0.001) (Figure 2). Additionally, a large main effect of task was found, showing that the greater distance led to more variability (F (1, 162) = 55,16, p < 0.001). Moreover, the statistical analysis revealed significant interaction effects between group and task for variability (F (2, 162) = 13.25, p < 0.001). Post hoc analysis of the CV showed that TD and m-DCD did not differ either for the short- (p = 0.52) or for the long-distance tasks (p = 0.33). The other post hoc comparisons for CV between TD and s-DCD and m-DCD and s-DCD were significantly different (p < 0.001). Eur. EJ.uIrn. vJ.e Isntviges.tHig.e aHltehaltPhs Pyscyhcohlo. lE. Edduucc. .2 2002244,, 1144, x FOR PEER REVIEW  7   1034   FFiigguurree 11. .DaDrta srctorsec oinr ethien twthoe cotnwdoiticoonns dfoirt itohne sthfroere gthroeupthsr. eSecogrerso aurpe slo. wSecro inre tshea lroenglo-dwisetranicne the long- dtaisstka cnocmeptaasrekdc toom thpea srheodrtt oditshtaensche.o The s-DCD group is poorest in the task. For the short-distance score, differences between TD and s-DrtCdDis, tTaDn caen.dT mh-eDsC-DDC, aDndg mro-uDpCiDs panodo rse-DstCiDn tahree stiagsnki.ficFaonrt the short- d(pis