Motor development for individuals with Down syndrome – An overview

doi:10.3104/9781903806173


2. What do we know about the development of motor skills in children and adults with Down syndrome?

Research into the development of motor skills in children and adults with Down syndrome is limited at the present time.[10,11,12] The available research can be divided into two main types – descriptive studies and experimental studies.

Types of research

The studies of infants and children are mainly descriptive. Descriptive studies usually document the ages at which skills are attained. These may be basic gross and fine motor skills, and sometimes recreational skills as well as component skills such as balance, or hand-eye coordination. There have been a small number of experimental studies of children but most of the experimental work has examined the skills of teenagers and adults. Experimental studies usually require participants to learn a new motor action or to carry out actions at speed and then measure various aspects of their performance.

Limits of research

Unfortunately, the findings of many research studies in the area of motor skills have to be interpreted with caution for several reasons.

Small numbers. Researchers have often studied very small numbers of children or adults. For example, one widely quoted study reports findings based on 2 children with Down syndrome in one age group and 4 in another.[4] Given the considerable variability of progress among children and adults with Down syndrome, it is impossible to judge how representative the performance of such small numbers of children actually is, and therefore whether the findings can be generalised to all other children and adults with Down syndrome.

Date of studies. Some studies from the 1970s and 1980s will include children who grew up with low expectations, little or no early intervention support, and limited social and educational opportunities. Early studies may therefore be difficult to interpret.

Comparison groups. Another weakness of many studies lies in the comparison groups that they use. Many studies of both adults and children compare their motor skills with typically developing individuals of the same chronological age, usually reporting significant differences in performance, with those with Down syndrome having 'poorer' skills. However, when the comparison group is matched on mental age, then there are often no significant differences in the overall motor performance of the groups. Any differences that are found tend to reflect strength and balance issues or speed and accuracy of performance, rather than overall motor control. Examples of these findings are given in the relevant sections later in this overview.

Motor development in children with Down syndrome

  • Motor skills develop in largely the same sequence as in typical children but later.
  • They improve with practice – but may need more practice and take longer to improve.
  • There is considerable individual variation in rates of progress.
  • The majority of children with Down syndrome achieve all the basic skills necessary for everyday living and personal independence.
  • Their fine motor skills steadily improve with practice and many can write, colour, draw and use a computer mouse and keyboard effectively.
  • Achievements in recreational skills vary but often seem to reflect family enthusiasms. Some children become very competent swimmers, skiers or gymnasts for example.
  • Most research suggests that their motor skills are similar to typically developing children of similar general mental ability (therefore younger).
  • However, balance seems to be a particular difficulty relative to progress in general coordination and muscle strength.

Learning and practice effects. One problem that arises when the motor skills of children or adults with Down syndrome are compared with those of others is that it is difficult to control for their past experiences and the opportunities that they have had to develop their motor skills. They will usually have had less opportunity to practise than those they are being compared with. Practice improves motor skills until an optimal level of skill is achieved which does not improve further. In research studies, it is only possible to draw conclusions about differences in motor abilities if the participants are able to practise until they reach their peak performance, and there is evidence that individuals with Down syndrome require significantly more practice than others to reach their peak performance (see 'Practice improves performance').

Practical relevance. A number of studies are of theoretical rather than practical relevance. Currently many researchers are interested in the detailed way in which movements are carried out by individuals with Down syndrome and they measure differences in the angles of joint movements, take measures of the actual activation patterns of muscles, or study the differences in patterns of gait. Most of these studies indicate largely normal movement patterns.[13-16] Some do indicate difference in muscle activation patterns[5,15,17] or joint movements in experimental situations. However, since no one has conscious control over the sequence of actions of muscles or joints when moving, these studies have little direct practical relevance. It is also not clear from most of these studies whether these differences are developmental (i.e. seen in the early stages of learning a skill) and will disappear with practice.

Descriptive studies

The pattern of motor development for children and adults with Down syndrome

One of the important issues in the study of motor development in people with Down syndrome is whether there is delay in achieving milestones and/or whether movements are abnormal or not properly suited for their purpose. Some of the relevant research is considered in this section.

Development is the same but delayed

Motor development for children with Down syndrome is usually significantly delayed. All the basic motor skills are achieved by infants and children with Down syndrome in mostly the same order, but usually at significantly older ages when compared with typically developing infants and children. This is illustrated by the examples given in Table 1.

Table 1. Motor Milestones - A guide to ages of attainment for children with Down syndrome [46]

Cunningham & Sloper [18] Berry et al
[19]         
Winders
[20]
Typical development
Attainment Range Average age (months) Range Average age (months) Range Average age (months)
Rolls 4 to 11 8 2 to 12 6 to 7 2 to 10 5
Sits steadily without support 8 to 16 11 7 to 16 11 5 to 9 7
Pulls to standing 10 to 24 17 8 to >28 17 7 to 12 8
Stands alone 16 to 36 22 - 21 9 to 16 11
Walks without support 3 steps or more 16 to 42 24 14 to 36 26 9 to 17 13
Grasps cube 4 to 10 7 - - 3 to 7 5
Passes object from hand to hand 6 to 12 8 - - 4 to 8 5
Puts 3 or more objects into cup/box 12 to 34 19 - - 9 to 18 12
Builds a tower of two 1 inch cubes 14 to 32 20 - - 10 to 19 14

There is evidence that some motor skills, such as those requiring fine finger to thumb opposition position (pincer grasp) and those requiring fine control of balance, may be achieved later than is typical and therefore slightly out of the usual sequence. One study of 220 young children with Down syndrome aged 3 months to 60 months[21] assessed their progress on specific gross and fine motor skills on the Bayley Scales of Infant Development. This test provides norms for the ages and expected sequence of the achievement of early motor skills in typically developing children. This study found that picking up tiny objects, walking backwards, standing on one foot, jumping and walking downstairs without support, were all achieved later than is typical, and late in relation to other motor skills. The reader may note that standing and walking were not relatively delayed, in fact both standing and walking 10 feet on tiptoes were achieved relatively early in the sequence. It seems that it is skills requiring more complex balance control that are achieved later. Balance is discussed more fully in the next section.

There is increased variability

There is greater variability in the basic motor progress of children with Down syndrome when compared with typically developing children. For example, the average age for walking in typically developing children is 13 months and the range is 9-17 months, while the average age for walking in children with Down syndrome is 24 months and the range is 14-42 months. Some of this greater variability may reflect the effects of health status for some children. Children with major heart abnormalities may be slower to achieve some motor milestones until they have corrective surgery, and the minority who cannot have corrective surgery will continue to be delayed. Similarly, a small number of children with Down syndrome have additional brain damage and will be more severely delayed in their motor progress. We need to study the progress of large numbers of children and take account of their health status, in order to develop sufficiently detailed data to enable parents and practitioners to accurately predict the progress to be expected of individual children.

Guides to expected progress

The figures provided in Table 2 may be a useful general guide to expected progress. They are based on a study of the gross motor progress of 121 Canadian children with Down syndrome aged 1 month to 6 years.[22] The figures give the percentage of children who are expected to achieve a skill at each chronological age point. The researchers in this study found that the children's rate of progress slowed between the ages of 3 and 6 years when they were learning to run, jump and climb stairs, confirming the findings of other studies that as the balance, speed and coordination requirements of movements increase, the children have relatively greater difficulty. However, these researchers also stress that while having Down syndrome did affect the rate at which new skills were mastered, it did not affect the upper limit of the skills achieved – most children can run, climb steps and jump by 6 to 7 years. It takes children with Down syndrome longer to reach a milestone and longer to refine and improve movements but, with enough practice and encouragement, they will achieve it.

Table 2. The percentage of children with Down syndrome expected to achieve skills at each age point. Adapted with permission from Elsevier [22 p.499]

Age (months)
Milestone 6 12 18 24 30 36 48 60 72
Rolling 51 64 74 83 89 93 97 99 100
Sitting 8 78 99 100 100 100 100 100 100
Crawling 10 19 34 53 71 84 96 99 100
Standing 4 14 40 73 91 98 100 100 100
Walking 1 4 14 40 74 92 99 100 100
Running 1 2 3 5 8 12 25 45 67
Climbing step 0 0 1 1 3 5 18 46 77
Jumping forward 0 0 0 1 2 5 18 52 84

Progress in teenage years

There is only one study reporting in detail on the motor progress of older children with Down syndrome and this does not provide any normative data for the achievement of particular scores but it does illustrate continued improvement for most children on most skills from 10 to 16 years.[23,24] In this study, information on the fine and gross motor skill development of 105 Australian children was studied over a number of years. The children were assessed at regular intervals on the Bruininks Oseretsky Test of Motor Proficiency (BOTMP) which has 8 subtests designed to assess:-

  1. Running speed and agility – the speed with which a child can run 13.7 metres, pick up an object and return to the start.
  2. Balance – a number of balance items such as standing on one leg with eyes open and closed.
  3. Bilateral coordination – a number of items requiring different limbs to be temporally coordinated e.g. synchronised tapping of the right finger and left foot or right finger and right foot.
  4. Strength – tasks requiring strength, including sit-ups and push-ups.
  5. Upper-limb coordination – items exploring ball skill and manual dexterity (e.g. finger/thumb opposition).
  6. Response speed – reaction times to a simple stimulus.
  7. Visual-motor control – items involving cutting, drawing and copying, without being timed.
  8. Upper-limb dexterity – items needing a sequence of manual movements e.g. posting coins through a slot, and requiring tasks to be completed within a time limit.

The BOTMP provides norms for the typical ages at which specific levels of performance on the tasks will be achieved and age-related scores can be computed for each of the 8 skill areas.

On all the skill areas the group showed some progress between 10 and 16 years. There was considerable individual variability and the rate of the children's progress was largely predicted by their mental age, rather than chronological age. While there was a close link between mental and motor age, with those with higher mental age scores tending to have higher motor age scores, on most motor subtests the group had significantly higher mean ages for motor skills. All the subtests scores are higher except for balance, which is lower, and response speed, which is at the level expected for mental age. It is difficult to know how to interpret these findings, as it is always difficult to draw firm conclusions when comparing age-equivalent scores in different areas of development when the tests used have been standardised on different groups of children at different times.

Looking at a subgroup of 16 boys and 13 girls for whom consistent longitudinal data was available, the boys scored higher than girls on running speed and agility, strength, and upper-limb coordination. While a number of the teenagers were reported to be overweight (the Body Mass Index Scores were analysed for the whole group), there was no measurable link between being overweight and motor skill achievements on the BOTMP tests at this early stage of adolescence.

Clumsiness and refinement of movements

Some authors observe that many movements continue to seem somewhat 'clumsy' in individuals with Down syndrome.[5] It takes them longer to improve their skills and they may not reach quite the same levels of fine coordination that most of us take for granted, but the levels they do achieve will usually be adequate for successful performance. Improvements in basic fine motor skills such as tying a shoelace or writing often continue to improve through early adult life. However, it is important to stress the wide variability in progress again, as many children and adults with Down syndrome do not seem at all 'clumsy' when walking, running, picking up a cup, writing, skiing, skateboarding or doing gymnastics. The final level of co-ordination and skill achieved seems to have much to do with encouragement and opportunities to take up sports and to practice. We know many individuals who have achieved high levels of competence in basic, recreational and employment skills, and therefore we should never assume that having Down syndrome necessarily puts an upper limit on what a particular individual may achieve.

More difficulty with balance and strength

A number of studies[2,9,13] indicate that balance is a particular difficulty and continues to be a weakness in teenage years.[23,24] This may explain why many young people with Down syndrome find riding a bicycle rather difficult to master. Some children do become competent on two wheels but many do not achieve this, although they may be very competent on a tricycle. In a recent study of a representative group of teenagers conducted by the authors, 93% could ride a tricycle and 36% could ride a bicycle.[44]

Strength also tends to be less even when the comparison is with young people of similar age and general mental abilities.[25,26] The explanation for this is not clear. Everyone increases their muscle strength through active movement and it could be that individuals with Down syndrome engage in less active movement, although there is no direct evidence of this. The babies, toddlers and children that we see regularly in our preschool and school services seem to us to be quite active. It could be that children with Down syndrome need more exercise to reach the same levels of strength. This is another area where we know from our practical experience that there are considerable individual differences, with some teenagers with Down syndrome being as strong or stronger than their non-disabled peer group in school. Teenagers who do gymnastics, karate or weightlifting, for example, can be as strong as non-disabled peers, so again, having Down syndrome per se does not impose upper limits on strength.

Experimental studies of movement skills

Studies which compare children or adults with Down syndrome with typically developing individuals of the same age almost always report differences or delays. These comparisons are of limited value as we need to know if these differences simply reflect developmental immaturity – that is, are the individuals with Down syndrome carrying out the task as a younger person of similar mental age would? This is the only way to identify any differences which would have a practical implication for therapy or teaching approaches. We have focused, therefore, on reporting studies that include mental age matched comparison groups and discuss some representative examples of these studies.

Laboratory studies of basic skills

Some experimental studies have looked in detail at the way in which basic skills such as reaching and grasping or walking are carried out by children and adults with Down syndrome, others have studied the ways in which they perform experimental movement tasks.

Reaching and grasping. In a study of reaching and grasping – the movements used throughout the day to handle objects, the skills of 12 children aged 8 to 10 years with Down syndrome were compared with two groups of typically developing children, one of the same age and one younger and mental age matched.[16] The researchers report that the performance of the children with Down syndrome was essentially the same as that of the younger children. They performed the tasks at the same speed and showed the same ability to adjust their grasps for the size of the object to be picked up as the younger children. They mostly showed the same use of a pincer grip, although 2 children with Down syndrome had unusual grasps, with a tendency to use the palm and all their fingers, rather than finger and thumb. There was more variability in the movement patterns, and a little less accuracy, which the researchers suggest indicates that more practice would be needed to establish more effective motor patterns. Overall, the study indicated that reaching and grasping were delayed rather than different. Similar findings, indicating the ability to adjust to the size of the object, are reported in another study of grasping in 4 to 11 year olds with Down syndrome.[40]

Walking. In a study of the walking patterns of children and adults with Down syndrome, 5 children aged 4 to 9 years and 3 adults of 30 to 38 years were compared with a typical adult of 22 years on several tasks, walking and running in bare feet on a hard floor, walking on the elastic surface of a trampoline and walking on a narrow beam. The researchers report [13 p.79,80] that the walking patterns of the children with Down syndrome on a hard floor were very similar to those of the adults with Down syndrome and the typical adult. The movements of their joints are described as showing 'very smooth trajectories' and to 'resemble adult patterns of walking'. The children and adults with Down syndrome also showed patterns of co-ordination similar to that of the typical adult when running. There was some evidence of differences in the precise details of the range of joint and limb movements but the overall picture was of effective, smooth and largely normal movement. As this study does not include any mental age matched children or adults for comparison, any reported differences may only indicate immaturity at this point. On the trampoline and the balance surfaces, the children and adults with Down syndrome had more difficulty. Both tasks require more skill in balance and they were less able to manage these tasks competently than the typical adult. The changes that they showed in their knee movements and step lengths were attempts to compensate for balance difficulties. Here again, with no mental age comparison and small numbers, the significance of these patterns cannot be interpreted. They could indicate ongoing difficulties with balance, and/or delayed progress.

Laboratory studies of specific movements

Slower reaction times

When teenagers and adults with Down syndrome are asked to perform motor tasks in experimental situations, such as tapping a particular button when a particular light comes on, their reaction times have been reported as slower than those of typical individuals of the same age and the same when compared with mental age matched controls.[see 14,15] However, in some studies there is a difference in reaction times for people with Down syndrome when instructions are visual rather than verbal. They show faster reaction times when instructions are visual and show significantly slower reaction times when the instructions are verbal. In everyday life, reaction times influence the speed of starting a movement from the time an instruction is given, for example, at the start of a race.

Slower movement times

Learning specific movements in experimental situations

When learning new movements and being expected to be as fast and accurate as possible, in comparison with others of a similar mental or general functional age, individuals with Down syndrome are usually:

  • Slower to react and initiate a movement
  • Slower to complete a movement
  • More accurate - make fewer errors

In addition:

  • Their reaction times improve with practice
  • They perform better when instructions are visual rather than verbal

Some studies have reported slower times (compared with mental age matched groups) for the movement component of tasks as well as the reaction time.[14,15] The movement time is the time taken from the initiation of the movement to reaching the end point of the movement – for example, the time taken from initiating the movement to completing the tap in the reaction time task. Individuals with Down syndrome show slower movement times on experimental tasks when instructions are verbal, but when instructions were visual, their performance was the same as mental age matched peers.[see 14] One research group suggests that this indicates a specific verbal-motor impairment in individuals with Down syndrome and that this may reflect different brain organisation for movement control,[27] but this hypothesis needs more research.

Delayed but visual learners

Overall, this group of leading movement researchers identify that research studies consistently show that the development of motor skills of individuals with Down syndrome is essentially delayed rather than different. It is linked to progress in general mental age and progresses in a typical but slower way, except for the specific difficulty in processing verbal instructions. They conclude therefore that "a developmental model of information processing and skill acquisition should be used to guide the instructional protocols used by clinicians, teachers and parents attempting to optimise skilled performance".[14 p. 67] The advice to use a 'developmental model' means that parents and teachers should expect movements to be achieved and improved in the same way as they are in typically developing children and adults, although more slowly. Teaching activities should, therefore, be those appropriate for the stage of movement skill that a child or adult has achieved. The practical implications of the verbal instruction findings are that, within a developmental framework, instructions for motor activities of all kinds, from writing to dancing, should be by modelling or demonstrating actions whenever possible. There are, in fact, studies showing that the motor areas of the brain which control movement are activated by passively watching a movement, which may partially explain the advantage of learning by watching, rather than by verbal instruction.[45]

Practice improves performance

Data from experimental studies requiring fine motor tasks to be carried out [6,15] and from real life studies of activities such as running,[28] report significant improvement in the performance of tasks with practice – improvements in both speed and accuracy of movements. For example, a group of adolescents with Down syndrome enrolled in a physical training programme showed considerable improvements as a result of training. The mean time to run the 50 metre dash dropped from 15.39 to 10.69 seconds. However, some of these studies concluded that individuals with Down syndrome require about twice as much practice to reach the same level as typically developing individuals of the same mental age.[28] They seem to need more practice to establish motor programmes.

The positive effects of practice are well illustrated in a series of studies[29-31] in which the researchers compared the performance of 10 adolescents with Down syndrome, average age 16 years, with that of 3 other groups of students; one group of the same age with learning disabilities but not Down syndrome, one group of typically developing high school students of the same age and one group of younger typically developing children of the same developmental age. The young people were asked to perform a pursuit–tracking task (see Figure 2) which requires them to move the pointer to the target light. The pointer is moved by turning the steering wheel and once the pointer has been on that target light for 200 milliseconds, the light goes off and another comes on. The pointer then has to be moved to that light. In one trial of 100 moves, the lights come on in a pattern that requires 50 moves to the right and 50 moves to the left. The probability of moving in a particular direction varies according to current position, as illustrated in Figure 2. If the pointer is on the far left light, there will be 100% probability that the next required move will be to the right and if the pointer is on the middle light, the probability of moving right or left is the same – 50%. The probabilities for each light are illustrated in the figure. In the studies, the researchers were interested in the speed (measuring both reaction time and movement time) and accuracy with which the young people could carry out the task, and whether they used the probability information to improve their performance.

Figure 2. Pursuit tracking device

Speed and accuracy

In the first study[29] the young people carried out 8 trials comprising 800 actual moves of the pointer. The young people with Down syndrome scored at the same level on reaction times as their peers with learning disabilities and both these groups were slower than the typically developing high school and elementary school students. On movement times the pattern was the same. However, on accuracy, the young people with Down syndrome were significantly better than all the other groups – therefore they were even more accurate than non-disabled peers of the same chronological age. They were slower than their non-disabled peer group but they made fewer errors. The mean error rate for the group with Down syndrome was 8%, and for the learning disabled and high school groups 13%. However, the young people with Down syndrome did not show any evidence of making use of probability data, that is, they did not react faster when it was possible to predict the likely direction of movement, although the other groups were able to do this.

Reaction times improve with practice

These researchers went on to extend this work[31] and in another study using the same groups and design, they increased the amount of practice to 24 trials and, therefore, 2400 moves. For reaction times, again, the typically developing high school students were faster, but the other 3 groups were not different from one another – that is, the young people with Down syndrome were as fast as the younger typically developing children and their peers with learning disabilities. This time, having been given much more practice at the task, the young people with Down syndrome did show evidence of using probability information when reaction times were analysed to take account of this, i.e. the more predictable the direction to move in for the next light the faster their reaction time. However, their reaction times continued to be longer for longer movements, and this is not easy to interpret.

Slower but more accurate

For movement times, the young people with Down syndrome were slower than all the other groups but again, they were more accurate – they made fewer errors than all the other groups.

When given sufficient training, the young people with Down syndrome significantly reduced their reaction times – they were about 36% faster in reacting and initiating movements, but they did not improve their movement times. They seemed to focus on accuracy and were unwilling to increase speed. This is entirely sensible as, in all studies looking at speed and accuracy on this sort of task, there is a link or 'trade-off' as a point is reached where it is not possible to improve one without a negative effect on the other; after this level of performance has been reached, an increase in speed leads to a decrease in accuracy (this is called Fitt's Law).

Individual differences

Within the group of 24 young people with Down syndrome who took part in one of the studies[30] using this task, the performance of individuals tended to be linked to general mental age, that is, those with higher mental ages did better on the tasks than those with lower mental ages.

The importance of practice

These general findings of improvement with practice, slower movement speeds and a focus on accuracy rather than speed have been confirmed in other studies.[see 15] Many studies indicate that teenagers and adults show considerable improvement with practice. This indicates that they have not yet reached their optimal levels of performance, possibly because they have not had enough opportunity to practise both gross and fine motor skills during childhood. In some studies, their performance after practice is as good as typically developing individuals of the same age.[5,43]

Why this profile of development?

At the present time, we do not have enough knowledge about the reasons for these features of motor development in individuals with Down syndrome but we do have several facts which may provide some clues and guidance for more effective intervention.

Closely linked to mental age

Both the descriptive studies of children's progress and some experimental studies of motor skills in adults identify that the motor performance of individuals with Down syndrome is closely linked to their general cognitive progress. In other words, for gross motor, fine motor and experimental tasks, they usually perform like other children or adults with the same cognitive or mental age. This suggests that the main effect is delay rather than difference in motor progress.

Early childhood

The close relationship between early mental and motor development is illustrated in the graphs in Figure 3. These graphs are based on 707 assessments of 220 children on the Bayley Scales of Infant Development.[32] A team of researchers pooled the data collected on children in Australia, Canada and Germany and some of the children had been assessed several times at different ages as they were involved in on-going longitudinal studies. This provided some 707 separate assessments covering the chronological age range from 3 months to 54 months. The reader can see that the group is progressing at a very similar rate in mental and motor development. The correspondence is exceptionally close at this age range and studies of older children show that the relationship holds into the teenage years.

Figure 3. Mental and motor progress in children with Down syndrome (Adapted from [32, p.339] with permission)

Later childhood

One American study charted the progress of 15 children with Down syndrome who were 7 to 10 years of age, and who had had the advantage of well-organised early intervention and education. The findings in Table 3 show the close relationship between their mental and motor progress. For the reader interested in the data, the correlations between the fine motor and gross motor skills and mental age are both .64 and statistically highly significant.[33] A study of 99 Australian 10 to 16 year olds with Down syndrome also showed the close link between motor skills and mental age, with the children's mental age rather than their chronological age, predicting performance and progress.[23,24]

Table 3. Relationship between mental and motor progress in children with Down syndrome. Based on data published in [33, Table 2, p.1317]

Range Mean
Mental age 3y 3m - 6y 6m 4y 8m
Gross motor age 3y 5m - 6y 0m 4y 9m
Fine motor age 4y 2m - 6y 2m 4y 10m
Note: The fine motor scores are based on 12 children, as three children with mental ages between 3 years 3 months to 3 years 9 months were not tested on the fine motor scale.

The reason for the close association of overall mental and motor development is not clear, but it may reflect that the control of motor skills is largely a central nervous system activity and that brain functions play a central role in motor development in the same way as they do in other aspects of development. It could be that both mental and motor development are delayed by similar differences in brain processes. One of these differences could be speed of information processing in the brain. Another could be the ability to establish learned programmes in the brain. A number of studies have highlighted the inconsistent performance of children with Down syndrome on both cognitive and language tasks. It seems to take them longer (i.e. they need more practice) to effectively consolidate new learning.[34]

Individual variability

The reader should note that the close link between the development of mental and motor skills indicated in these studies does not mean that this close correspondence will apply to every individual child at any particular stage. For example, a particular three year old with Down syndrome may be making rapid progress with language but still not be walking, another three year old may show the opposite profile, walking but not yet talking. The overall mental and motor age scores used in these studies are each based on a large number of tasks to give an overall picture of mental and motor development and there will be variability in the way individual children achieve their overall scores. However, the link between overall mental age and progress in overall motor skills is a powerful trend in all studies that have looked at both, and is clearly of significance in understanding the issues.

More dependent on visual feedback

Researchers have reported that children and adults with Down syndrome rely more on visual feedback while carrying out a task than typically developing individuals.[see 9,35] They may need to rely to a greater extent on visual feedback because they take much longer to establish learned motor programmes for the task. This can make their performance seem as if they are tackling each repetition of the task as if they have not performed it before. It also means that their pattern of movement may be jerky and inconsistent from one time to the next even though they can actually perform the task correctly. This finding could explain longer movement times because, as a learned programme is established, the sequence of movements required for a movement can be performed more quickly.

Balance

As already identified, there is some evidence that balance may be a particular difficulty for individuals with Down syndrome. In one experimental study, the balancing abilities of infants with Down syndrome were compared with typically developing infants and the two groups were carefully matched for their ability to stand unsupported.[9] The infants were put into a small room in which the floor was stable but the walls could be moved to give the impression of the room tilting. All the infants reacted as if the floor was also tilting by leaning, swaying, staggering or falling, that is, they reacted as if to stop themselves from falling even though the floor they were standing on did not move. The visual information suggested they were being tilted even though the vestibular and proprioceptive feedback would not have suggested this.

The children with Down syndrome were more affected and made larger postural adjustments than the typically developing children. Both groups of children improved as they increased their experience of walking and after some 12 months of walking the typically developing children were finally able to stay stable in the tilting room and not react to the false visual cues. The children with Down syndrome needed longer to become stable and did not show complete stability after a year or more of walking experience, even though they were improving. The authors suggest that these findings indicate that children with Down syndrome are more dependent on visual cues to judge body position than typically developing children at the same stage of walking, because they need extra visual information to compensate for less effective vestibular and proprioceptive feedback at this stage.

Another similar study of 26 older children with Down syndrome (mean age 10.6 years) showed that they were still more affected by this kind of experience and showed more body sway than other children of the same age. [41]

There is other evidence to suggest that balance continues to be an area of specific difficulty into the teenage years. In an Australian study of the motor skills of 81 twelve year olds,[23,24] balance was the weakest area and still at a 4 year level when their other motor skills range from 5 to 9 year levels. Their mean mental age was 4 years 9 months and therefore most of the motor skills for the group were higher than might be expected, with response speed at the same level as mental age and only balance lower than mental age. There was considerable variability in motor skills between individuals and, as in other studies, mental and motor skills were related. Individuals with lower mental ages tended to have lower motor skill scores, and vice versa.

Physical differences

Many authors assume that the profile of motor development in Down syndrome is largely the result of physical differences, but the evidence for this point of view is limited. Almost every discussion of motor development in children with Down syndrome starts with descriptions of hypotonia and lax ligaments, and suggests that they are to blame for the motor delays.

The significance of hypotonia

At birth, babies with Down syndrome are observed to be more 'floppy' than other babies.

This has been described as hypotonia but there is no agreed definition of hypotonia.

There seems to be evidence for:

  • lower muscle 'tone', defined as either less resistance to passive movement or feel softer if pressed – both unsatisfactory as there are no precise measures and no comparisons with mental age matched infants without disabilities.
  • 'lax ligaments', implied by the fact that limbs can be more widely rotated – there is more movement in the joints allowing children to take up unusual postures such as widely splayed hips when moving on floor or sitting.

Both muscle 'tone' and 'lax ligaments' improve with age and with movement.

There is no convincing evidence that these factors affect movement ability, i.e. the brain may be compensating for them when child moves.

However, it has been suggested that they may affect the development of movements if child takes up odd postures or tries to move limbs differently in the early stages of learning a movement – studies are needed on this issue.

Hypotonia and lax ligaments

Many newborn children with Down syndrome have very flaccid muscles and are described as 'floppy'. There are many specific disorders which are associated with the birth of 'floppy' infants; in some cases this disappears as the child develops and in some cases they remain in this 'floppy' state. There are a few follow up studies of infants with Down syndrome and it seems that this infant floppiness does improve over time. There is a fairly widespread belief that the children remain with a degree of hypotonia and this state is often invoked as being responsible for much of the 'poor' motor function seen in people with Down syndrome.

However, this is a rather controversial issue since there is no proper agreement as to the definition of hypotonia and there is no consensus as to how to measure it. In addition, some recent studies have demonstrated that the hypotonia seen when children and adults with Down syndrome are not moving (i.e. their tendency to have more 'floppy' muscles at rest) is not evident when they are moving and does not actually impair coordinated movement.[see 8,15]

It is generally accepted that ligaments and tendons in individuals with Down syndrome are more 'stretchy' than is usual. This would explain why they are often able to move their joints into extreme positions. However, research indicates that this does not prevent coordinated control of the joints to perform ordinary movements.[8,15] Both muscle 'tone' and 'lax ligaments' improve with age and with movement, and there is no convincing evidence that these factors affect the development of movements, i.e. the brain is likely to be compensating for them as the child moves.

Clearly, a great deal of research needs to be done to clarify the different contributions of the stretchiness of ligaments and tendons, the strength of the muscles, the 'tone' of the muscles and the contribution of the nervous input to the greater picture of motor function in individuals with Down syndrome.

Health issues

Some authors rightly draw attention to a number of medical conditions that are more common in individuals with Down syndrome and which may affect a child's or adult's ability to be active, if not effectively treated.[10,11,36] These include heart conditions, underactive thyroid function, vision and hearing issues, atlanto-axial instability and obesity. It will be important to take account of health factors for individual children and adults when considering active sports but most will not prevent progress in basic gross or fine motor skills. The relevance of each of these illness conditions for activity will be the same as it is in the rest of the population.

Health and physical issues which may affect movement

Health and physical issues may account for some of the individual differences in progress among children and adults with Down syndrome.

Any specific medical conditions will have the same effects as they would in typically developing individuals.

However, babies or children with Down syndrome may have more difficulty in compensating for these effects.

Individuals with Down syndrome may be at a greater risk for:

  • Sensory impairments:
    Visual impairments – may reduce feedback on position, and depth and distance perception.
    Hearing impairments – will make following instructions more difficult.
  • Uncorrected heart abnormalities – may significantly reduce energy and stamina.
  • Atlanto axial instability – minority issue which has been exaggerated, but parents, teachers and sports instructors should be aware of the risk in order to spot symptoms rather than to restrict activities.
  • Obesity – may reduce enjoyment of movement; healthy diets and exercise should be encouraged for the same reasons as for everyone else.

Individuals with Down syndrome tend to be small in stature, with short arms and legs, and small fingers when compared with the typical population – this will have the same effects on movement and on recreational choices as it does for small people in the general population.

Parents and carers are likely to know about their children's medical and healthcare needs and will inform teachers and therapists. Some authors also draw attention to the tendency for individuals with Down syndrome to have small stature and small hands relative to typically developing individuals. However many, if not most, have similar stature to those at the small end of the general population and the restrictions this imposes on achievements in sports will be the same for both groups. More information on health issues for children with Down syndrome can be found in each age-specific overview in the DSii series – see Resources list.

In summary

See also:

The movement skills of children with Down syndrome are largely delayed rather than different and progress at the same pace as their general mental development. They may take longer and need more practice to improve their performance and they may continue to have more difficulty with tasks requiring balance. Most children achieve competence in all everyday gross and fine motor skills even though they develop more slowly. Despite the presence of lax ligaments and possible hypotonia, there is little evidence that they impair controlled movements as the central nervous system controls all movement and usually compensates for such variables.

Teenagers and adults with Down syndrome may be slower to perform movements in some situations, possibly reflecting slower information processing in the central nervous system and/or a focus on accuracy and safe, effective movements rather than on speed.[5]