Motor performance of children with mild intellectualdisability and borderline intellectual functioningjir_1318 955..965
P. J. Vuijk,1 E. Hartman,1 E. Scherder2 & C. Visscher1
1 Center for Human Movement Sciences, University Medical Center Groningen, University of Groningen,the Netherlands2 Clinical Neuropsychology,VU University, Amsterdam, the Netherlands
Background There is a relatively small body ofresearch on the motor performance of children withmild intellectual disabilities (MID) and borderlineintellectual functioning (BIF). Adequate levels ofmotor skills may contribute to lifelong enjoyment ofphysical activity, participation in sports and healthylifestyles. The present study compares the motorskills of children with intellectual disability (ID) tothe abilities observed in typically developing chil-dren. It also aimed to determine whether there isan association between degree of ID and motorperformance.Methods A total of 170 children between 7 and 12years old with MID or BIF, who attended schoolsfor special education, were examined on the testcomponent of the Movement Assessment Batteryfor Children (MABC) test. Both groups were com-pared with the norm scores of the total score, sub-scale scores and individual items of the MABC test.Results Of the children, 81.8% with MID and60.0% with BIF performed below the 16th percen-tile on the total score of the MABC. Both groups
demonstrated a relative weakness in the area ofmanual dexterity. Comparisons between bothgroups showed small to moderate effect sizes on thetotal score of the MABC, as well as for all threesub-scales, favouring the children with BIF.Conclusions Children with ID had significantlymore borderline and definite motor problems thanthe normative sample and there was an associationbetween degree of ID and performance of manualdexterity, ball skills and balance skills. This studyhighlights the importance of improving motor skillperformance in both children with borderline andmild ID, and the results support the notion that thelevel of motor and cognitive functioning are relatedin children with ID.
Keywords atypical brain development, borderlineintellectual functioning, mild intellectual disability,motor performance, Movement Assessment Batteryfor Children
The American Association on Intellectual andDevelopmental Disorders (formerly known asAmerican Association on Mental Retardation)defines intellectual disability (ID), previouslyreferred to as mental retardation, as characterized
Correspondence: Mr Pieter Jelle Vuijk, Center for Human Move-ment Sciences, University Medical Center Groningen, Universityof Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, theNetherlands (e-mail: firstname.lastname@example.org).
Journal of Intellectual Disability Research doi: 10.1111/j.1365-2788.2010.01318.x
volume 54 part 11 pp 955965 november 2010955
2010The Authors. Journal of Intellectual Disability Research 2010 Blackwell Publishing Ltd
by significant limitations both in intellectual func-tioning and in adaptive behavior expressed in con-ceptual, social, and practical adaptive skills. Thisdisability originates before the age of 18. (Schalocket al. 2007, p. 118). Pratt & Greydanus (2007)elaborated on this definition by stating that indi-viduals with ID have limitations in developmentalskills in several domains of functioning includingcognitive, motor, auditory, language, psychosocial,moral judgment and specific integrative adaptiveactivities of daily living. Even though deficits inmotor functioning are mentioned above, there issurprisingly little research in this domain on indi-viduals with ID, particularly children with ID.Whenconsidering that adequate levels of motor skills maycontribute positively to activities of daily living(Watkinson et al. 2001), lifelong enjoyment of physi-cal activity, participation in sports (Wall 2004;Krombholz 2006) and less sedentary behaviour(Wrotniak et al. 2006), it is important that motorfunctioning in children with ID is examined.Previous research has focused mostly on ID with
a known aetiology, such as Down syndrome (i.e.Vicari 2006),Williams syndrome (i.e. Tsai et al.2008) and children with a more profound ID (i.e.Van der Putten et al. 2005), but not on childrenwith a mild intellectual disability (MID), defined aschildren with an intelligence quotient (IQ) scorebetween 50 and 70 (American Psychiatric Associa-tion 2000). This limited body of research is particu-larly striking considering that the estimations of theprevalence of MID is around 3.4% (Roeleveld et al.1997).Some early research, that focused on children
with MID, showed delays in the development ofmotor skills (Francis & Rarick 1959; Rarick 1973;Bouffard 1990). For example, children with MIDappear to be 35 years behind in gross and finemotor skills in comparison with typical functioningchildren of the same age (Rarick 1973). Hagberget al. (1981) found that 23% of the children in agroup of Swedish school children with MID wereidentified with clumsy child syndrome (a formerterm for children with motor impairment; i.e. Sig-mundsson 2005). Savage (2007) examined a groupof children with ID (IQ < 70) on two motor tasksfrom the dyslexia screening test (Fawcett & Nicol-son 1996). The first motor task was bead threadingthat was used as a measure of dynamic cerebellar
functioning and the second task was postural stabil-ity that was used as a measure of static cerebellarfunctioning. The scores for children with ID werebelow the normative scores on bead threading butnot on the postural stability task. The lack of effectin the second task may be attributed to the fact thatthe postural stability task is a qualitative measureof balance, which may very well differentiate lesscompared with the more quantitative measure offine motor skills found in bead threading. Morerecently, Wuang et al. (2008) examined a total of233 children with MID aged 78 years on 22 mea-sures of sensorimotor functioning. Around 44% ofthe children scored in the impaired range on sevenout of 22 measures.The limited body of research on motor perfor-
mance in children with MID also applies to chil-dren with borderline intellectual functioning (BIF),which includes children with an IQ between 71and 84 (American Psychiatric Association 2000).Although this is a significantly large group of chil-dren, comprising up to 7% of the school age popu-lation (Karande et al. 2008), there is similarly littleresearch in this area (Ninivaggi 2001; Kaznowski2004), and little research specifically on childrenwith BIF and their motor functioning. Two studieshave addressed motor functioning in children withBIF (Hetrick 1979; Karande et al. 2008). In theformer study, children with BIF performed poorlycompared with typically functioning peers of thesame chronological age on the Bender visualmotortask (Koppitz 1964). In the latter study, of a groupof 55 children with BIF, 27.3% showed delays inwalking and 92.7% demonstrated difficulty withwriting.All the studies above compared a group of intel-
lectually disabled individuals against the norms ofthe general population, a sample of individualswhose intellectual function is within normal limitsor typically functioning individuals with an isolatedlearning disability (LD). Considering the relativelysmall body of research on motor functioning ofchildren with ID, we wanted to explore two newapproaches. First, we compared two groups of chil-dren who are adjacent to each other in the spec-trum of intellectual functioning, one with MID andthe other with BIF, with the norms of the generalpopulation.These groups of children with slightlydifferent intellectual functioning were assessed on
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2010The Authors. Journal of Intellectual Disability Research 2010 Blackwell Publishing Ltd
all eight items of the MABC thus creating a broadview of their status of motor development. Second,the groups were compared with each other in anattempt to get an insight into potential differencesin motor development between these two groups.In typically developing individuals a relationshipbetween the acquisition of motor milestones andsubsequent cognitive functioning at the ages 8, 26and 53 has been observed (Murray et al. 2007).Murray et al. suggested that the mechanism explain-ing their results was a suboptimal corticalsubcortical connectivity. Another study, by Reisset al. (1996), also suggested a relationship betweencognitive functioning and particular brain areas.Using a brain imaging study, they found that IQwas positively correlated with cerebral volume inchildren, in particular with cortical grey matter inthe prefrontal region of the brain. Based on theirresults, we expected to find a difference in motordevelopment between the MID and BIF groupfavouring the latter group. A possible difference inmotor functioning between children with MID andBIF would suggest an extension of the atypicalbrain development (ABD) concept by Kaplan et al.(1998). ABD is a conceptual framework for under-standing developmental LDs and its high co-morbidity with other developmental disorders, suchas developmental coordination disorder (DCD),pervasive developmental disorder not otherwisespecified (PDD-NOS) and attention deficit hyper-activity disorder (ADHD), by claiming that the
aetiology of developmental disorders is an atypicalfunctioning of the brain. At this time, ID is notincluded in this framework. A lower degree of intel-lectual functioning would mean a higher degree ofmotor impairment. In order to examine thesehypotheses using an ecologically valid sample withregard to variety in intelligence and co-morbiditywe recruited children from two elementary schoolsfor special education.
We recruited 190 children with ID from twoelementary special needs schools in the northernregions of the Netherlands. Twenty children whowere ill during the measurements and childrenwithout informed consent from their parents wereexcluded.The final study population included 170children aged 712 (109 boys, 61 girls; mean age10.0 years, standard deviation 1.4 years) (Table 1).IQ scores, extracted from the personal files of thechildren, were used to classify the children intoMID (50 IQ 70, n = 55) and BIF groups(71 IQ 84, n = 115) according to the Diagnosticand Statistical Manual of Mental Disorder IV TextRevision (American Psychiatric Association 2000).Forty-four children across both groups were alsodiagnosed with PDD-NOS and 30 children withADHD.The groups did not statistically differ from
Table 1 Characteristics of the childrenwith mild intellectual disability (MID)and borderline intellectual functioning(BIF)
MID(n = 55)
BIF(n = 115) Test statistic
Mean (SD) Mean (SD) t (168) P-value
Age 9.93 (1.41) 10.06 (1.37) 0.59 0.56IQ 65.27 (4.56) 77.38 (4.12) 17.32
each other on age, gender, % ADHD or % PDD-NOS. Informed consent for the childrens participa-tion was obtained from the parent(s) and allprocedures were in accordance with the ethicalstandards of the Faculty of Medical Sciences of theUniversity Medical Centre Groningen, Universityof Groningen.
In order to assess motor performance, the test com-ponent of the Movement Assessment Battery forChildren (MABC; 1st edition) was applied (Hend-erson & Sugden 1992).We used the MABC as it isa standard exam used worldwide for the evaluationof children with movement difficulties (Smits-Engelsman et al. 1998, 2008). Smits-Engelsmanet al. (1998) showed that the norms of the MABCare satisfactory for Dutch children. In this study,the Dutch validated version was used (Smits-Engelsman 1998).The MABC consists of four age-related item sets
(46, 78, 910 and 1112 years). Each age bandconsists of eight items, which are assessed under thefollowing sub-scales: manual dexterity (three items),ball skills (two items) and static and dynamicbalance (three items). Some items are performedwith the preferred hand as well as the non-preferredhand. Hand preference can be defined as the handthe child uses for writing (Henderson & Sugden1992). Each item is scored on a scale from 0 to 5.Summing the item scores for every subtest providesa sub-scale score. The manual dexterity score variesfrom 0 to 15; the ball skill subtest score from 0 to10; and the static and dynamic balance subtestscore from 0 to 15. Sub-scale scores can besummed to give a total score for motor develop-ment ranging from 0 to 40. High scores indicatepoor motor performance.The total score on the MABC, as well as the sub-
scale scores and item scores were converted intopercentile scores that reflected the childs level ofperformance in comparison with children in thenormative population. Children with a scorebetween the 100th and 16th percentile wereregarded as having no motor problems, 15th to 6thpercentile as having borderline motor problemsand the 5th percentile and below as having definitemotor problems.
The MABC has acceptable validity and reliabil-ity in children from regular schools and schoolsfor special education (Henderson & Hall 1982;Lam & Henderson 1987; Van Waelvelde et al.2004). Inter-rater reliability ranges from 0.70 to0.89 and the testretest reliability is 0.75 (Hender-son & Sugden 1992). The MABC has been usedin a wide range of study populations, such as chil-dren with Down syndrome (Spano et al. 1999),children with LDs (Van Waelvelde et al. 2004),children born prematurely (Jongmans et al.1997), deaf children (Gheysen et al. 2008) andchildren with visual impairments (Houwen et al.2008).
The items of the MABC were administered indi-vidually by master students in Human MovementScience. The test leaders were thoroughly trainedin the test before the data collection (trainingincluded familiarisation with all procedures andscoring methods). MABC testing was carried outaccording to the manual of this test. Appropriateage bands were used for all children. Within theMID group 12 children completed the items ofage band 2, 17 children the items of age band 3and 26 children the items of age band 4. Withinthe BIF group, 16 children completed the items ofage band 3, 52 children completed the items ofage band 3 and 47 children completed the itemsof age band 4. There was no statistical differencein the distribution of the children over the threedifferent age bands across groups (c2(2) = 3.64;P = 0.16).
Data analysis was conducted using spss forWindows 15.0. The motor performance of the chil-dren was classified as no motor problems, border-line motor problems (below the 15th percentile) ordefinite motor problems (below the 5th percentile)in comparison with the percentage expected in anormal population.This was done for the totalscore and the sub-scales of the MABC as well asfor the individual items.The distribution of theclassifications in our sample was tested by use of ac2-test. To examine the difference on motor perfor-mance between the childre...