**1. Introduction**

According to ICD – 10 (1993) there are two big groups of specific developmental disabilities: learning disabilities and motor disabilities. The first includes a group of disorders which characterize problems in school achievement, especially in reading and math. The second includes a group of disorders in motor coordination, balance, lateralization, which cannot be explained by general problems in intellectual development or any other specific neurological disorder. The etiology of these disorders is unknown, but there is a hypothesis that they are the consequence of interaction between biological factors and the influence of social environment, as much as interaction between those two factors and quality of educational processes.

Motor skills play a crucial role in the social and emotional functioning of a child and may impact quality of life and well being (Poulsen, Ziviani, Johnson & Cuskelly, 2008; Skinner & Piek, 2001; Sleeuwenhoek, Boter & Vermeer, 1995; Verrips et al., 1999, as cited in Houwen et al., 2009b).

Williams et al. (2008) found that preschool children with poorer motor skill performance were less active than children with better-developed motor skills. They concluded that the relationship between motor skill performance and physical activity could be important to the health of children, particularly in obesity prevention.

The results of research (Šarenac, 1999; Nikolić et al., 2000; Urošević, 2001) conducted with early childhood age children in regular primary school show that 10-15% of children with poor motor skills have low school success. These children need support to overcome developmental and learning difficulties.

Barnet et al. (2009) assessed children's proficiency in object control (kick, catch, throw) and locomotor (hop, side gallop, vertical jump) skills with the aim of investigating whether skill proficiency predicts subsequent physical activity. The research results indicate that object control proficient children were more likely to become active adolescents. According to these authors motor skill development should be a key strategy in childhood interventions aiming to promote long-term physical activity.

With the aim of further understanding control impairments seen in children with developmental coordination disorder (DCD) and the effect of these impairments on motor

Motor Skill Performance of Children with Sensor Impairments 219

differences may aid those working with deaf children in physical education. Horak et al. (1988) examined vestibular status and motor proficiency of 30 hearing-impaired and 15 motor-impaired learning-disabled children to determine whether vestibular loss can account for deficits in motor co-ordination. Reduced or absent vestibular function in 20 hearingimpaired children did not affect development of motor proficiency, except in specific balance activities. However, sensory organization deficits in the learning-disabled group and in three of the hearing-impaired children were associated with widespread deficits in motor proficiency. A few studies related to motor skill performances of persons with hearing impairment indicate that, with the exception of balance impairment, there are no significant differences in this area between persons with hearing impairment and those who can hear (Garet & Levin E, 1970). But, the research conducted by Vujasinović (1997), states that the children with hearing impairment show the delaying in motor development. Depending on age, this delaying varies from 8 months (at the age of four), to two years and nine months at the age of eleven. The delaying in motor development in relation to the chronological age increases with the age itself. Narančić (1997) examined practognostic organization of children with hearing impairment and showed that, generally speaking, their abilities to master the psychomotor performance in the service voluntarily given model were not reported. Butterfield (1986) evaluated and summarized the gross motor development of 132 hearing-impaired children between the ages of 3 and 14 year. Delays were noted in catching, kicking, jumping and hopping. It was determined that gross motor skill performance was not related to etiology of deafness or to the sex of the subjects. Rine et al. (2000) also found evidence of delayed gross motor development regardless of age, but only children less than 5 years1 of age had developmental balance deficits on initial testing. Both gross motor and balance development scores were lower on repeated testing. Kohen-Raz and Masalha (1988) found significant correlations between the basic arithmetic and motor skills, within the hearing as well as within the hearing-impaired groups; these remained significant even within the small subgroups of the latter. Thannhauser et al. (2001), examined psychomotor efficacy of children with hearing disorders. It was found that children with impaired hearing reach worse psychomotor efficacy in the range of hand movement co-ordination and precision. Psychomotor efficacy examined at particular age undergoes development and sex was not a differentiating factor, and compared environments were not univocally found to influence the development of the examined features. In a study aimed at examining motor performance in deaf elementary school children and its association with sports participation, Hartman et al. (2011) found that the deaf children had significantly more borderline and definite motor problems than the

normative sample: 62% (manual dexterity), 52% (ball skills) and 45% (balance skills).

sensorineural hearing impairment.

As routine screening for children with hearing impairment does not include assessment of balance and motor deficits, physical therapy services are not included in the educational programme, unless obvious neurological or orthopaedic disorders are diagnosed. However, teachers and parents of these children often report incoordination, clumsiness and balance deficits which may hinder the child's optimal performance (Butterfield, as cited in Rajendran & Roy, 2011). Moreover, many paediatric health care providers are often too busy or inadequately trained in conducting elaborate developmental screening tests during the

1 In this study gross motor development was examined in 24 to 83 - month-old children with

performance in these children, Grovea and Lazarusb (2007) assessed 30 children with and without DCD. It was found that children with DCD had greater difficulty maintaining postural control when visual and somatosensory feedback were compromised in sensory conflict environments (p = .031). Group differences in postural control were independent of age. It was pointed out that their results demonstrated that impaired ability to utilize vestibular feedback while re-weighting somatosensory and visual feedback for orientation may be responsible, in part, for the postural control impairments observed in some children with DCD.

Coordination, balance, body position sense and motor sequential organization are not in themselves prerequisites to academic success. The effectiveness of gross motor output plays a role in personality development. Youngsters who are not able to compete in team sports will generally lack a sense of "motor mastery" and may suffer from diminished self-esteem, social rejection and general feelings of inadequacy. Gross motor disabilities may be the outward indicators of central nervous system dysfunction. A history of difficulty catching a ball, general awkwardness, poor balance and trouble learning to ride a bicycle, to hop and to skip may lead one to suspect a gross motor lag (Abroms, 1980, as cited in Nikolić & Ilić-Stošović, 2009).

The detection of motor skill disorders then is an important indicator of delayed or lower quality motor maturity. Prompt inclusion of these children into treatment programmes prevents mild disorders from developing marked difficulties in school (Nikolić & Ilić-Stošović, 2009).

The problem becomes more complex when considering the terms of sensory impairment influence on the motor skill performances.

Childhood hearing impairment is a significant public health problem which is associated with long-term academic and communicative difficulties (Davis, 1997, as cited in Rajendran & Roy, 2011). Children with hearing impairments have a higher risk for deficits in balance and gross motor skills compared with children who are developing typically. As balance is a fundamental ability for the motor development of children, a valid and reliable assessment to identify weaknesses in balance is crucial (De Kegel et al., 2010).

Research results related to motor skill performances of children with hearing impairments are very different. Cushing et al. (2008) found that large differences existed in the balance ability of children with sensorineural hearing loss requiring cochlear implantation compared with age-matched controls (children with normal hearing). Implant activation, however, conferred a slight advantage in accomplishing balance-related tasks. An et al. (2009) examined the relation between age and single-limb standing balance in children with and without deafness, and concluded that the postural stability of profoundly deaf children improves as a result of adaptive sensory compensation, both visual and somatosensory. In addition, it appears that postural control is more highly dependent upon visual input than on somatosensory input. Gayle and Pohlman (1990) measured the dynamic, static and rotary balance of deaf and hearing children. Significant differences were noted between groups for dynamic balance and rotary balance. Although not significant, there was a difference of 57.8% in a number of trials for successful completion of static balance in favour of the hearing children. In the present study, overall balance in deaf children was significantly inferior to the balance in hearing children. The authors highlight that knowledge of these

performance in these children, Grovea and Lazarusb (2007) assessed 30 children with and without DCD. It was found that children with DCD had greater difficulty maintaining postural control when visual and somatosensory feedback were compromised in sensory conflict environments (p = .031). Group differences in postural control were independent of age. It was pointed out that their results demonstrated that impaired ability to utilize vestibular feedback while re-weighting somatosensory and visual feedback for orientation may be responsible, in part, for the postural control impairments observed in some children

Coordination, balance, body position sense and motor sequential organization are not in themselves prerequisites to academic success. The effectiveness of gross motor output plays a role in personality development. Youngsters who are not able to compete in team sports will generally lack a sense of "motor mastery" and may suffer from diminished self-esteem, social rejection and general feelings of inadequacy. Gross motor disabilities may be the outward indicators of central nervous system dysfunction. A history of difficulty catching a ball, general awkwardness, poor balance and trouble learning to ride a bicycle, to hop and to skip may lead one to suspect a gross motor lag (Abroms, 1980, as cited in Nikolić & Ilić-

The detection of motor skill disorders then is an important indicator of delayed or lower quality motor maturity. Prompt inclusion of these children into treatment programmes prevents mild disorders from developing marked difficulties in school (Nikolić & Ilić-

The problem becomes more complex when considering the terms of sensory impairment

Childhood hearing impairment is a significant public health problem which is associated with long-term academic and communicative difficulties (Davis, 1997, as cited in Rajendran & Roy, 2011). Children with hearing impairments have a higher risk for deficits in balance and gross motor skills compared with children who are developing typically. As balance is a fundamental ability for the motor development of children, a valid and reliable assessment

Research results related to motor skill performances of children with hearing impairments are very different. Cushing et al. (2008) found that large differences existed in the balance ability of children with sensorineural hearing loss requiring cochlear implantation compared with age-matched controls (children with normal hearing). Implant activation, however, conferred a slight advantage in accomplishing balance-related tasks. An et al. (2009) examined the relation between age and single-limb standing balance in children with and without deafness, and concluded that the postural stability of profoundly deaf children improves as a result of adaptive sensory compensation, both visual and somatosensory. In addition, it appears that postural control is more highly dependent upon visual input than on somatosensory input. Gayle and Pohlman (1990) measured the dynamic, static and rotary balance of deaf and hearing children. Significant differences were noted between groups for dynamic balance and rotary balance. Although not significant, there was a difference of 57.8% in a number of trials for successful completion of static balance in favour of the hearing children. In the present study, overall balance in deaf children was significantly inferior to the balance in hearing children. The authors highlight that knowledge of these

with DCD.

Stošović, 2009).

Stošović, 2009).

influence on the motor skill performances.

to identify weaknesses in balance is crucial (De Kegel et al., 2010).

differences may aid those working with deaf children in physical education. Horak et al. (1988) examined vestibular status and motor proficiency of 30 hearing-impaired and 15 motor-impaired learning-disabled children to determine whether vestibular loss can account for deficits in motor co-ordination. Reduced or absent vestibular function in 20 hearingimpaired children did not affect development of motor proficiency, except in specific balance activities. However, sensory organization deficits in the learning-disabled group and in three of the hearing-impaired children were associated with widespread deficits in motor proficiency. A few studies related to motor skill performances of persons with hearing impairment indicate that, with the exception of balance impairment, there are no significant differences in this area between persons with hearing impairment and those who can hear (Garet & Levin E, 1970). But, the research conducted by Vujasinović (1997), states that the children with hearing impairment show the delaying in motor development. Depending on age, this delaying varies from 8 months (at the age of four), to two years and nine months at the age of eleven. The delaying in motor development in relation to the chronological age increases with the age itself. Narančić (1997) examined practognostic organization of children with hearing impairment and showed that, generally speaking, their abilities to master the psychomotor performance in the service voluntarily given model were not reported. Butterfield (1986) evaluated and summarized the gross motor development of 132 hearing-impaired children between the ages of 3 and 14 year. Delays were noted in catching, kicking, jumping and hopping. It was determined that gross motor skill performance was not related to etiology of deafness or to the sex of the subjects. Rine et al. (2000) also found evidence of delayed gross motor development regardless of age, but only children less than 5 years1 of age had developmental balance deficits on initial testing. Both gross motor and balance development scores were lower on repeated testing. Kohen-Raz and Masalha (1988) found significant correlations between the basic arithmetic and motor skills, within the hearing as well as within the hearing-impaired groups; these remained significant even within the small subgroups of the latter. Thannhauser et al. (2001), examined psychomotor efficacy of children with hearing disorders. It was found that children with impaired hearing reach worse psychomotor efficacy in the range of hand movement co-ordination and precision. Psychomotor efficacy examined at particular age undergoes development and sex was not a differentiating factor, and compared environments were not univocally found to influence the development of the examined features. In a study aimed at examining motor performance in deaf elementary school children and its association with sports participation, Hartman et al. (2011) found that the deaf children had significantly more borderline and definite motor problems than the normative sample: 62% (manual dexterity), 52% (ball skills) and 45% (balance skills).

As routine screening for children with hearing impairment does not include assessment of balance and motor deficits, physical therapy services are not included in the educational programme, unless obvious neurological or orthopaedic disorders are diagnosed. However, teachers and parents of these children often report incoordination, clumsiness and balance deficits which may hinder the child's optimal performance (Butterfield, as cited in Rajendran & Roy, 2011). Moreover, many paediatric health care providers are often too busy or inadequately trained in conducting elaborate developmental screening tests during the

 1 In this study gross motor development was examined in 24 to 83 - month-old children with sensorineural hearing impairment.

Motor Skill Performance of Children with Sensor Impairments 221

of the children with severe visual impairment is approximately equal to the development of the children who can see, except for the tasks requiring specific experience. The skills in fine motor coordination and the success in mastering spatial relations were found out to develop spontaneously in the visually impaired children who had adequate opportunities for rough motor activities and who were allowed to freely research their environment, although usually in a later age than in children without visual impairment. A similar conclusion can be found at Warren (1994) who indicated that variables linked to impaired vision, such as environmental opportunities and barriers for movement, rather than vision impairment per se, have an impact on the motor skill performance of persons with visual impairment. Houwen et al. (2009) reviewed 39 studies, 26 of which examined the effects of child, environmental and/or task variable (sell) on motor skill performance, 13 of which reported suggestions by experts about variables related to performance. In this review study weak evidence was found for three relationships: (a) between the degree of visual impairment and the performance on dynamic balance and manual dexterity (Gipsman, 1981; Houwen et al., 2008; Leonard, 1969; Pereira, 1990; Reimer et al., 1999; Ribard et al., 1987; Wyver & Livesey, 2003 as cited in Houwen et al., 2009b); (b) between amblyopia/strabismus and fine motor skills (Caputo et al., 2007; Hrisos et al., 2006; Weber et al., 2008, as cited in Houwen et al., 2009b); (c) between movement interventions and motor skill performance (Aki et al., 2007; Dye, 1983; Jospeh, 1984; Lieberman, Stuart et al., 2006; Palazesi, 1986; Poncillia et al., 2005, as cited in Houwe et al., 2009b). In addition, weak evidence was found to refute a relationship between gender and static balance (Leonard, 1969; Pereira, 1990; Ribadi et al., 1987, as cited

As it could be seen through reviews of previous studies, motor functioning of children with

Every limitation or poor motor skill performances, in their own way disturbed the process of integration in school and threatens effectiveness of participation in educational activities. Poor motor skill may lead to poor performance in physical activities, which may reduce a child's sense of competence. This may lead to withdrawal of movement activities that would, in turn, lead to limited opportunities to practice motor skills and participate socially

The aim of this research is to establish the prevalence, form and the quality of motor skill performance in children with sensor impairment. The research results will focus on two groups of school aged children: children with visual impairment and children with hearing impairment. First, the findings on variables associated with prevalence, form, level of motor disorders and quality of motor skill performances are analyzed in each group of children. "*Motor skill performance* is a broad term which is defined as the observable act of movement and task characteristics (Hutzler, 2007; Newell, 1986; Shumway-Cook & Wollacott, 2001; Warren, 1994; WHO, 2001, as cited in Houwen et al., 2009b). *Motor skills* are acts or tasks dependent on practice and experience for their execution (Payne & Isaacs, 2002, as cited in Houwen et al., 2009b). In the purest sense, the term motor refers to underlying biological and mechanical factors that influence movement (or observable action), however, the terms movement and motor are frequently use interchangeably (Gabbard, 2007; Sherill 2004, as

in Houwen et al., 2009b).

**2. Method** 

sensory impairments can be very variable.

(Skinner & Piek, as cited in Houwen et al., 2009b).

cited in Houven et al., 2009b, pp. 467)".

regular clinics. These tests are performed only when the child presents with an obvious deficit (Omondi et al., 2007 as cited in Rajendran & Roy, 2011).

From the other side vision plays an important role in motor skill performance as vision guides and controls the acquisition, differentiation and automatization of motor skills (Brambring, as cited in Houwen et al., 2009). Functions of visions in motor skill acquisition are (a) incentive function - to motivate children to move, (b) spatial function - to provide information about distance and direction of movements and objects, (c) protective function to anticipate dangerous situations, and (d) controlling/feedback function - to detect errors and correct the ongoing movement by online regulation of the movement. Furthermore, vision enables children to imitate movements made by others (Brambring, 2006, as cited in Houwen et al., 2009b, pp. 465). The objective of Taylor Kulp's (1999) study was to examine the relationship between visual motor integration skill and academic performance in kindergarten through to third grade. The children's regular classroom teachers rated the children with respect to reading, math and writing ability. Second and third grade children were also rated on spelling ability. They found that performance on a visual analysis and visual motor integration task is significantly related to academic performance in 7, 8 (reading, writing and math achievement ratings) and 9 year olds (writing, spelling and math achievement ratings). Performance on the visual motor integration was found to be significantly related to teachers' ratings of the children's reading, math, writing and spelling ability.

The visual control is necessary for all targeted movements in the function of their correction. The children with visual impairment at the earliest age have badly expressed and incoordinated movements of hands, they are passive and show a low curiosity for the objects in their surroundings. As we could read, there are a lot of studies that are related to the motor skill performances of children and adolescents with visual impairment. Jablan (2003), examined the motor skill development quality of elementary-school age children with severely visually impairment. It was found that 55.8% of children had harmonious development of motor functions. The most difficulties were found within melokinetic praxia and the coordination of bi-manual activities. Houwen et al. (2009a) examined the physical activity levels of children with and without visual impairments. It was further investigated whether the degree of visual impairments was associated with activity level, whether body composition was associated with activity level and whether interrelationships existed between activity level and motor skill performance. All participated children (96) were ages 6 to 12 years and attended mainstream schools. It was found that total activity was significantly higher in children without visual impairment than in children with visual impairment. Participation in moderate to vigorous physical activity was significantly higher in children without visual impairments versus children with visual impairments. Light activity was positively associated with locomotor scores; total activity and moderate to vigorous physical activity were positively associated with object control scores. For children without visual impairments, total activity and time spent in moderate to vigorous physical activity were positively associated with locomotor scores and time spent in sedentary activity was inversely associated with object control scores. The authors concluded that the results of their research emphasize the importance of promoting an active lifestyle in children. Special attention has to be paid to children with lower visual acuities and children with higher body mass index. From the other side, the research conducted by Norris, Spaulding and Brodie (1957) (as cited in Garet & Levin, 1970) indicates that the development of the children with severe visual impairment is approximately equal to the development of the children who can see, except for the tasks requiring specific experience. The skills in fine motor coordination and the success in mastering spatial relations were found out to develop spontaneously in the visually impaired children who had adequate opportunities for rough motor activities and who were allowed to freely research their environment, although usually in a later age than in children without visual impairment. A similar conclusion can be found at Warren (1994) who indicated that variables linked to impaired vision, such as environmental opportunities and barriers for movement, rather than vision impairment per se, have an impact on the motor skill performance of persons with visual impairment. Houwen et al. (2009) reviewed 39 studies, 26 of which examined the effects of child, environmental and/or task variable (sell) on motor skill performance, 13 of which reported suggestions by experts about variables related to performance. In this review study weak evidence was found for three relationships: (a) between the degree of visual impairment and the performance on dynamic balance and manual dexterity (Gipsman, 1981; Houwen et al., 2008; Leonard, 1969; Pereira, 1990; Reimer et al., 1999; Ribard et al., 1987; Wyver & Livesey, 2003 as cited in Houwen et al., 2009b); (b) between amblyopia/strabismus and fine motor skills (Caputo et al., 2007; Hrisos et al., 2006; Weber et al., 2008, as cited in Houwen et al., 2009b); (c) between movement interventions and motor skill performance (Aki et al., 2007; Dye, 1983; Jospeh, 1984; Lieberman, Stuart et al., 2006; Palazesi, 1986; Poncillia et al., 2005, as cited in Houwe et al., 2009b). In addition, weak evidence was found to refute a relationship between gender and static balance (Leonard, 1969; Pereira, 1990; Ribadi et al., 1987, as cited in Houwen et al., 2009b).

As it could be seen through reviews of previous studies, motor functioning of children with sensory impairments can be very variable.

Every limitation or poor motor skill performances, in their own way disturbed the process of integration in school and threatens effectiveness of participation in educational activities. Poor motor skill may lead to poor performance in physical activities, which may reduce a child's sense of competence. This may lead to withdrawal of movement activities that would, in turn, lead to limited opportunities to practice motor skills and participate socially (Skinner & Piek, as cited in Houwen et al., 2009b).
