Systematic Review on Executive Functions in Children with Poor Motor Skills and With Development Coordination Disorder

Objective: The aim of this study was to describe the tests used to assess working memory, inhibition, and cognitive flexibility, and analyzed the main research results related to executive functions in children with Developmental Coordination Disorder or with poor motor skills. Methods: This review used as data sources studies in MEDLINE, Web of Science, APA PsycNET, EMBASE, and Google Scholar with children with poor motor skills, DCD, and typical development. Quality of the studies was conducted using the Newcastle Ottawa Scale. Results: 1475 papers found, 31 matched the review criteria; 31 different executive function tests used to assess children with poor motor skills and DCD. Across the 31 studies, included in this systematic review, eleven studies examined only the working memory; ten studies measured only inhibition, a single study measured only cognitive flexibility, three studies examined the working memory and inhibition, one study examined inhibition and cognitive flexibility, one study examined working memory and cognitive flexibility and four studies examined the three executive functions. In conclusion, many tests were used to assess children with poor motor skill and DCD requiring verbal, nonverbal, or complex visuospatial processing, with or without motor demand involved. In some tests the different demands or different types of stimulus involved cause secondary loss in execution. The executive functions deficits in children with poor motor skills and DCD are in a wide ranging and extend across basic all functions assessed (working memory, inhibition, and cognitive flexibility). The pervasive and persistent nature of the executive function deficits suggests a need for a more aligned methodological approach to investigate this phenomenon.


Introduction
The Developmental Coordination Disorder (DCD) can present itself in an isolated manner, with the child showing difficulties in executing motor skills [1], or associated with academic contents [2], and movement planning (Brown-Lum & Zwicker, 2015; Zwicker et al., 2012)difficulties. Social and emotional [3], and cognitive development [4] are also affected. The close relation between motor and cognitive development is explained by cerebral areas activation, when motor control areas show neural activation during the execution of an movement certain cognitive areas are also coactivated (Diamond, 2000). Moreover, there is evidence of a specific relation between motor delays and deficits in executive functions [5].Executive functions are cognitive processes that allow the individual to direct behaviors to goals, evaluate the efficiency and adequacy of these behaviors, abandon inefficient strategies in favor of others that are more efficient, and solve immediate and long term problems [6]. Executive functions, therefore, regulate human behavior [7] by find the solution of problems, selective inhibit a behavior, control and change an action, and remember components necessary to act [8]. The executive functions are studied in three main components, the working memory (i.d. storing and updating information while the individual does some activity related to it), working memory"[All Fields] OR "verbal working memory"[All Fields]), inhibition("Inhibitory control"[All Fields] OR "inhibitory function"[All Fields] OR "Response inhibition"[All Fields] OR "Inhibitory controls"[All Fields] OR "inhibition"[All Fields]), and cognitive flexibility("cognitive flexibility"[All Fields] OR "Flexible cognition"[All Fields] OR "Shifting"[All Fields] OR "Set-shifting"[All Fields] OR "mental flexibility"[All Fields]). Executive functions were associated with keywords regarding the motor skills difficulties ("Developmental Coordination Disorder"[All Fields] OR "Motor Disorder"[All Fields] OR "DCD"[All Fields] OR "Dyspraxia"[All Fields] OR "Motor Skill Disorder" OR "poor motor skill" [All Fields]);none filters were used. We extracted categories for background (aim of the study and construct or domain of the executive function), methods (instruments or procedures for assessing the executive function, samples age,sex,number of participants with and without DCD, motor tests and cut off points used; confounding factors), and main findings and other relevant information reported by studies.

Assessment of Study Quality
The quality of the studies was assessed using the Newcastle/ Ottawa Scale (NOS: Takahashi & Hashizume, 2014);each study was evaluated using the point system. Two authors did a critical evaluation of the included studies for potential sources of bias (selection bias, detection bias, reporting bias, performance bias, attrition bias), methods of participant allocation and allocation concealment, and blind assessment. Study design was assessed regarding selection (representativeness of the sample, sample size, description of groups, ascertainment of exposure), confound comparability (based on design and analysis), and outcome (assessment of outcome and statistical test) considering recognize cut offs points, maximum score of five for cross-sectional studies (5 = very good; 4 = good; 3 = satisfactory; 0-2 = unsatisfactory) and eight for cohort studies (7-8 = very good; 5-6 = good; 4 = satisfactory; 0-3 = unsatisfactory). The two raters achieved consensus through discussion (K=0.90); the third author settled discrepant results.

Results
In the selection process, we identified 1475 papers using title and abstract screening; 31 matched review criteria. Approximately 90.3 % (n = 28 studies) were conducted within the last 10 years. In addition, 33 different tests to assess executive function were found within 31 studies. Sample sizes, including children with DCD or poor motor skills, ranged from 11 to 71 participants from England, Germany, Australia, Italy, Canada, France, Finland, Taiwan, and US. Figure 1 provided a selection process synthesis.

Inhibition Measurements in Children with DCD or Poor Motor Skills
Descriptive studies were first conducted, regarding inhibition and motor development, using the Simon Task [13].Latter on, the Go/no-Go test [14], the Stop-Signal Task and Day/Night Stroop tests (Livesey, Keen, Rouse, & White, 2006;Pratt et al., 2014), and the Verbal -Motor Inhibition tests [15] were used with the same objective. Yet, the Covert Orienting of Visuospatial Attention Task (COVAT) were used to investigate the associations spatial attention and motor difficulties [16]. The Go/no-Go test and neuroimaging was used to investigate the neural processes of inhibitory control in children with DCD [17]; and also in a experimental study investigating the impact of a neutral or positive reinforcement in inhibitory control of children with DCD [18]. And finally, Animal Stroop Task was used to compare results between children at risk for DCD and typical children [19].
Regarding intervention studies, two were conducted for children with DCD using Posner Paradigm to investigate changes in inhibition [20]; the visuospatial selective attention paradigm provides a measurement of conflict resolution that has been acknowledge as a trustworthy index of inhibitory control [21]. Two follow-up studies conducted during one-year [22]and two-years [23], assessed inhibitory control in children with and without motor difficulties using the Fruit Stroop Task test; and another studied conducted in England used the Verbal and Motor Inhibition tests to assess association of inhibition, poor motor skills and academic achievement in two-years follow-up study [24].

Working Memory Measurements in Children with DCD or Poor Motor Skills
Regarding to descriptive studies, working memory has been investigate in children with DCD in relation to the proficiency of motor skills using the Trail Making Test [25] the N-Back task [26,27]; and the Automated Working Memory Assessment [28]. Yet, a study investigated the visuospatial working memory mechanisms using the Visuospatial Working Memory Paradigm (VSWM) and compared the brain activity (electroencephalography) of typical and atypical children [29]; and the relation between motor coordination and visuospatial working memory in children with DCD, was investigated using the Cog State One-Back [30]. To verify attention and working memory in children with poor motor skills, the Cambridge Neuropsychological Test Automated Battery was used [31]. To compare results between children at risk for DCD and TD children three verbal and three visuospatial tasks were used [32].
A study conducted in England [33] investigate several executive functions in children with poor motor skills and DCD, using the Working Memory Battery for Children [34] to assess verbal

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working memory and the Odd-One-Out test [35] for the nonverbal working memory. Yet, a studied conducted in Italy using the Motor Observation Questionnaire for Teachers to investigate the relation between the poor motor skills and visuospatial working memory in children with DCD [36]. Regarding to a follow-up studies, a one-year [37] and two-years [38] studies assessed visuospatial working memory using the Backwards Color Recall task and the Corsi-Blocks Backwards tests. And another follow-up study used the Working Memory Battery for Children and Odd-One-Out in children with poor motor skills and DCD children over 2 years [38].

Cognitive Flexibility Measurements in Children with DCD or Poor Motor Skills
Deficits in cognitive flexibility tasks were assessed in children with DCD using an Inspection Time Task in an Australian study [39]. The Wisconsin Card Sorting test [40] and the Wisconsin Card Sorting Test has been developed to assess reasoning and the ability of changing cognitive strategies in response to environmental changes. Regarding to follow-up studies, in a one-year study the Cognitive Flexibility Test was used [41] and in a two-years period the Flanker Task [42] were used to assess cognitive flexibility in children with DCD. Another study conducted in France used the Trail Making Test [43] to compare the development of cognitive flexibility in children with motor difficulties. And the Intra-Extra Dimensional Test Set Shift to follow-up changes in nonverbal cognitive flexibility of the children over 2-years period [44]. Table 1 provided the main results of the testes used to measure executive functions in children with poor motor skill and DCD. Table 1 describes the tests and outcomes in studies design to assess executive functions in children. Inhibition

Simon task
The participant is told that they should press the button on the right when they see something red appear on the screen, and the button on the left when they see something green. Participants are usually told to ignore the location of the stimulus and base their response on the task-relevant color. This task consists of the presentation of a target set (i.e. the letters A, B, C, and D), with the actual target presented being an ordered rotation of these four letters. Participants must differentiate if: (1) the letter presented on the computer screen is a member of the target set (i.e. A, B, C, or D) and (2) if it is the current target. Some letters are designated as 'Go' or 'No-go' and are displayed in 1s intervals. When a Go stimulus is presented it is necessary to press a button and inhibit when a new stimulus is presented. Verbal and visuo-spatial working memory were measured using tasks involving simultaneous storage and processing of information. One example of a verbal working memory task is counting recall, in which the participant counts the number of target items in each of a series of successive arrays and then recalls the totals for each array in the original sequence. Visuo-spatial working memory tasks include rotating images and recalling their locations. This task consists of the presentation of a target set (i.e. the letters A, B, C, and D), with the actual target presented being an ordered rotation of these four letters. Participants must differentiate if: (1) the letter presented on the computer screen is a member of the target set (i.e. A, B, C, or D) and (2) if it is the current target. This is a task where the length of a line is discriminated, and the time of visual inspection is checked to correctly discriminate a type of stimulus.
Mean time/ number correct answers Mean time/ number correct answers 11 (Querneet al.,

2008) Inhibition Go/No-Go Task
The task requested of participants was to press a reply key to any letter presented sequentially (Go), except X (No-go). According to Casey et al. (1997), its design allows to isolate the brain regions involved in the suppression of the motor response (Go-No-go) This task consists of the presentation of a target set (i.e. the letters A, B, C, and D), with the actual target presented being an ordered rotation of these four letters. Participants must differentiate if: (1) the letter presented on the computer screen is a member of the target set (i.e. A, B, C, or D) and (2) if it is the current target. Some letters are designated as 'Go' or 'No-go and are displayed in 1s intervals. When a Go stimulus is presented it is necessary to press a button and inhibit when a new stimulus is presented.

Backwards Color
Recall task

Fruit Stroop task
Children are informed that their task is to feed two families of fish consecutively. They must feed one member of one family and one member of the other family in sequence. Each time one of the two fish appeared the child must decide who it was to feed instead of the previous action.
A sequence of colored disks was presented to the children on a computer screen and the children were asked to recall the sequence in reverse order.
It is a task with images of four different types of fruit and vegetables presented so that colors are named as quickly as possible in congruent or incongruent assays. Working memory N-Back Task The task is done from the presentation of the examinee to a stimulus that must be stored, at the same time as it should evoke the stimulus presented to him either a (1-back), two (2-back) or three (3-back) positions.
The children were asked to compare the positions and directions of the ladybirds in the rectangles. In two spatial memory tasks, the rectangles and ladybirds appeared following a 3-second or a 6-second delay. The visuospatial attention paradigm The pupils were black-filled circles inside the eyes and were centered vertically to the eyes. When cuing, the pupils were just touching the right or left side of the eye (valid, invalid, and catch trials) or were centered (neutral and catch trials) in the eyes Reaction times and response accuracy 19 (Chen; Wilson; Wu, 2012a) Inhibition COVAT -Covert orienting of visuospatial attention task The cueing task has been used to measure manual and eyemovement reaction times to target stimuli to investigate the effects of covert orienting of attention in response to different cue conditions. In the first part, the child learns to produce a response to the « red » stimulus (place a red chip when the child hears the word « red »). In the second part, the child must change the response pattern and respond to contradicting stimuli (place a red chip when hearing the word « yellow »).
The children had to compare the positions and directions of the ladybugs in the rectangles; (ii) two spatial memory tasks with a 3s-delay or (iii) with a 6s-delay, where the rectangles and ladybugs appeared with the respective delays. Working memory

Corsi blocks test
Participants were asked to recall a sequence of blocks just indicated by the experimenter in the same (forward) or in reverse (backward) order.

Knock-Tap task
The participants should state the color of the ink in which a word was printed (for example, the word "blue" printed in red ink; "red" response).
The task requires participants to place the non-dominant hand on the table and use the dominant hand to complete certain actions that the researcher explained at the beginning of each set of trials.
Total correct trials Inhibition Go/no-Go ("cool and hot").
Neutral facial expressions were used for the cool task, while the stimuli for the hot task were happy and fearful faces of the same individuals. The task included pictures of neutral/ calm, happy, and sad facial expressions of a group of men and women. Children were asked to respond (by pressing the spacebar) as quickly as possible to only that expression, and not the other.
Participants recall the last word of a sentence after making a judgement as to whether the sentence was true or false, with the number of sentences increasing as the task continues.
Participants recall the spatial location of a nonsense shape after making a judgement as to which of the shapes was the 'odd-one-out' Participants copy a word said by the experimenter, or provide another word (i.e. inhibit the copying response), depending on instructions Participants copy an action demonstrated by the experimenter, or provide another action (i.e. inhibit the copying response), depending on instructions Participants have to draw a line between numbers and letters in sequence, switching between the two (e.g. 1-A-2-B, etc.) Participants learn a rule through initial trial and error in relation to a shape and then must switch to a different rule to continue achieving 'correct' answers Go/no-Go ('cool' and 'hot').

Corsi-Blocks Backwards Task
Go/no-Go Task

Flanker Task
The task included pictures of neutral/calm, happy, and sad facial expressions of a group of men and women. Children were asked to respond (by pressing the spacebar) as quickly as possible to only that expression, and not the other.
A series of colored discs is presented for 2 seconds per disc. After the trial, a circle with all the colored discs is presented and the child must tap the correct sequence of colors (on a touchscreen) in reverse order There are numbers on the Corsi-blocks that only the administrator can see. The administrator touches some blocks and the child must touch the blocks in the inverted order immediately after presentation.
The test requires a participant to perform an action given certain stimuli (press a button -Go) and inhibit that action under a different set of stimuli (not press that same button -No-Go).
In the first part (the standard Flanker task), children have to react to a red fish that appears on-screen and are told to press the right or left button, according to the direction in which the fish is facing. An additional task set was added to the second part of this task: when appears yellow fish the child has to react according to the direction of the four-flanking fish (rule switching).

Omission Errors and Reaction Time
Mean of sequences correctly recalled The longest sequence correctly recalled. Participants recall the last word of a sentence after making a judgment as to whether the sentence was true or false, with the number of sentences increasing as the task continues.

Total errors
Participants recall the spatial location of a nonsense shape after making a judgment as to which of the shapes was the 'odd-one-out' Participants copy a word said by the experimenter, or provide another word (i.e. inhibit the copying response), depending on instructions Participants copy an action demonstrated by the experimenter, or provide another action (i.e. inhibit the copying response), depending on instructions Participants have to draw a line between numbers and letters in sequence, switching between the two (e.g. 1-A-2-B, etc.) Participants learn a rule through initial trial and error in relation to a shape and then must switch to a different rule to continue achieving 'correct' answers Consist on three verbal and three visuo-spatial tasks. The verbal tasks were: forwards word recall, selective word recall and verbal dual task and The three visuo-spatial tasks were: pathway recall, selective pathway recall and visuo-spatial dual task.
The computerized task showed images on a laptop and recorded the responses and reaction times.A child was required to name stimuli appearing on the screen.
For each subtestchildren were given a score of 1 for each correct performance The number of correct responses to incongruent stimuli and times of execution for each trial were recorded.
The studies used three motor batteries to assess children motor skills; the majority of the studies (n=22) studies used the Movement Assessment Battery for Children-2, five studies used a Mc-Carron Assessment of Neuromuscular Development-MAND. Some assessments (Bruininks-Oseretsky Test of MotorProficiency-2, KörperkoordinationstestFür Kinder) and interviews and questionnaires (multidisciplinary assessment of developmental dyspraxia, Motor Observation Questionnaire for Teachers, Ideomotor test questionnaire) were used with less frequency. Regarding the main results of the executive functions in children with poor motor skills or DCD compared to children with typical development the majority of the studies indicate that there is a deficit of inhibition in children with DCD, however effect size was rarely reported. Regarding, inhibition tasks 15 studies compare children with DCD with a typical development; three studies (code 13,25,26) found no difference between groups. One study (code 26) showed that children with DCD and with typical development had similar accuracy in Go/No-go tasks and similar errors during the task, except when the No-go stimulus was associated with conditions receiving positive reinforcement.
Regarding working memory, 15 studies compare children with DCD with children with typical development and only one study (code 14) found no difference between groups. Regarding cognitive flexibility tests, 6 studies were found comparing children with DCD or with poor motor skills with children with typical development. The results showed deficits in cognitive flexibility in children with DCD or with motor difficulty, independently of tests used, compared to control group. Table 2 presents themain results of the studies that assessed executive functions in children with poor motor skill and DCD.Insert Table 2 Using the NOS parameters, five studies implemented experimental design with very good quality; and 26 cross-sectional designs, ten with very good quality, nine with good quality, and the remaining six studies were satisfactory due to the lack of procedures adopted to control the influence of the researcher's knowledge about the sample in relation to the measurement of the outcome. However, in general, the methods of recruitment of subjects, controlling for the confounders, and outcome assessment were appropriate for all studies.  There was an association between the motor capacity and the task of executive function that investigates working memory; Motor performance does not appear to be linked to inhibitory control deficits but may involve temporal deficits related to the cerebellum. The relationship between motor performance and stop-signal task performance was in the expected direction but did not reach significance. Children with DCD performed poorly in all areas, particularly with low scores on visuospatial memory tasks. Specifically, language impairments were associated with selective deficits in verbal short-term and working memory, whereas motor impairments (DCD) were associated with selective deficits in visuospatial short-term and working memory. Children with attention problems were impaired in working memory in both verbal and visuospatial domains, whereas the children with AS had deficits in verbal short-term memory but not in any other memory component. Children with DCD obtained a similar score for correct inhibitions compared to the control group, but the responses were slower and with more variability than in the control group. Inhibition and shifting performance were consistently lower, compared to the children without motor coordination impairments For the Backwards Color Recall task, there were no differences between children with and without motor coordination deficiency.
Children with low levels of motor coordination reacted more slowly in the tasks of inhibitory control compared to the control group, but not in relation to the precision of the action. The present study demonstrates an important relationship between throwing and receiving skills in sports games, working memory and academic performance.  Children with DCD showed no impairment in spatial information processing but exhibited a deficit of retrieval of geographic information when performing the visuospatial working memory task. The ADHD + DCD group was slower to complete the task of spatial working memory compared to the ADHD group. Children with movement difficulty, fine motor skills significantly predicted later One-Back accuracy and speed. One-Back accuracy at baseline predicted better fine and gross motor skills following the 18-month period. The motor difficulties and DCD groups scored below the control group on nonverbal tests of working memory. The DCD and low motor performance groups had results below the typical group of children in non-verbal inhibitory control tests. There were no significant differences between DCD and motor difficulties groups with the group of typical children in the tasks of cognitive flexibility. Children with DCD have difficulty modulating their approach to rewarding stimuli when the task demands inhibited behavior. Risk for DCD = 18 (9 boys and 9 girls TD = 18 (9 boys and 9 girls) Significant differences were found between children at risk for DCD and TD children on cold EF tasks of visuospatial working memory abilities, fluency and inhibitory control, but not on hot EF tasks.

Discussion
Executive functions play a critical role in everyday life. However, despite the obvious relevance of executive functions of children with poor motor skills and DCD, much is still unknown about individuals 'ability. We addressed this gap in the literature by conducting a systematic review to identify tests used to measure inhibition control, cognitive flexibility and working memory. A large number of tests were designed to measure inhibition in children with typical development, with poor motor skills and with DCD. A possible explanation is the fact that inhibition presents a greater representation about the other possible components in executive functions. In other words, the satisfactory development of inhibition is essential for the typical performance of the other neuropsychological abilities, such as working memory, internalization of speech, self-regulation, reconstitution, and motor control [45].Inhibition studies with children with DCD, showed 158 a great variety of tests used, however the Go/No-Go test were used more often (3 studies) to assess a participant's capacity for sustained attention and inhibition behavior. Yet, in studies using neuroimaging to investigate the neural processes of inhibitory control of children with DCD, the Go/No-test was used [46]. Besides that, two versions, "cool Go/No-Go test" (the stimulus were faces with neutral facial expressions) and "hot Go/No-Go tests" (the stimulus were happy or fear emotions faces) were used to investigate the effects of this motivational strategy in the inhibition outcomes of children with DCD [47].
The diversity of tests used in the researches may be due to the multiple components of the executive functions and the lack of methodological agreement in the field [48]. In terms of inhibition control and working memory some tests were used to assess both functions (i.e. the trail making/updating task used by [49] while some other researchers used separate tests for these two functions [50]. It is also important to notice that the tests also differ in the extent to which they required motor skills, with tests such as the trail making/updating task requiring button pressing responses, while the Fruit Stroop task used having no motor demands [51]. Motor demands may mask the outcomes for the executive function. It would be worth mentioning that other factors such as the lack of executive function "purity" of the tests, tests interaction with age, and other aspects of inhibition could also play an important role in the test outcome [52]. For example, results indicate that there is no relation between the Stop-Signal Task with other assessment of inhibitory control in children five-to six-years-old [53]. There is an agreement that the Stop-Signal and the Day/Night Stroop tests present aspects that are very different regarding the inhibition of behavior in children with DCD; the lack of association between both tests do not pose any doubt about the validity of the tasks as a measurement of response inhibition. Another important condition refers to tests that involve motor demands. Many tests used to assess executive functions in children require verbal, nonverbal or complex visuospatial processing, with and without motor demands. In some tests, the different demands and types of stimulus may cause secondary loss during the execution, masking the primary executive function that should be examined (motor performance or visual perception bias) and limiting the acquisition of specific information. For example, inhibition tests was often involve press a button or other kind of motor responses, therefore in this kind of tests it is important to assess the extent to which any motor difficulties or additional processing load were associated with producing the responses effects on the inhibition performance of children with DCD [54].Consequently, researchers should ensure that they account for the tests of visuospatial and motor demands when interpreting the results of children with DCD [55]. The studies review underlined wide ranging of deficits across working memory, inhibition, and cognitive flexibility in children with poor motor skills and DCD compared to children with typical development; these deficits have been previously reported [56]. Specifically, since inhibition contributed to an efficient performance of several executive function by allow the motor execution to be fluent and efficient [57], this cognitive function is essential for tasks that suddenly prevent one's self from executing an inappropriately prepared action such as riding a bicycle, playing dodge ball or football [58]. Deficits in this control process underline motor coordination problems [59]. For instance, additional taps in a motor inhibition test with children with DCD could reflect a deficit in motor control resulting in involuntary repetition of the taps of the same thumb [60].This assumption is in accordance with previous studies showing a global inhibition deficit in tasks that not requiring a motor response in DCD [61]. Consequently, clumsiness could partially result from executive functions deficit demonstrated by children with DCD resulting from early cerebral lesion [62].
Regarding working memory, the majority of studies found deficits for children with poor motor skills and DCD. Working memory is an temporary information storage system that allows the management of information, and is related to the retention of the information in the brain and to the possibility of using clues of this information to solve a problem [63].This retention capacity makes us capable of connecting unrelated elements as well as separating integrated elements [64] which support the fact that children with poor motor skills and DCD have worse results than children with typical development. These processes of disassembly and recombination of the elements are fundamental for creativity and decision making [66]. Children with DCD were significantly slower and had greater variability in performance of cognitive flexibility tests compared to the typical develop children. Cognitive flexibility requires the individuals to modulate their behavior and adapt to different requirements of a particular tests [67] and change the course of actions according to the environment' requirements [68].
This capability suggests a change in perspectives or differentiated approaches to a problem, flexibility, adjusting to the demands, rules, or priorities of each task providing the basis for higherorder functions such as planning and reasoning [68]. However, cognitive flexibility appears later in the development compared to working memory and inhibition [69], which may be the reason for a smaller number of studies found and the absence of differences between the children with DCD and with typical development. For future studies, it would be important to standardize the tests and the methods in research enrolling children with poor motor skills and DCD, to enable more precise evidences. Although, practically it may be difficult to achieve since different measures of executive function are used across countries. We also argue that there may be moderators of the associations between poor motor skills and executive functions that are unaccounted in analyses. Some studies failed to report important information such as clinical status of participants, education, economic status, medication, psychiatric disorders precluding moderator analyses on these variables. However, it is worth emphasizing that the multiple characteristics and the recognized the overlap of different comorbidities of this disorder is a great challenge [70]. Yet, to further the understanding of the association between executive function and motor skills, the definitional and measurement problems of the executive function need to be solved [71]. Without a set of clearly defined terms and measurements, it will be difficult to be more assertive about how executive function relates to children poor motor skills [72].