Course:KIN366/ConceptLibrary/MotorAsymmetries

Movement Experiences for Children
KIN 366
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Instructor:	Dr. Shannon S.D. Bredin
Email:	shannon.bredin@ubc.ca
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Motor Asymmetries are characterized by lateral limb dominance/preference in humans (and sometimes animals) in regards to movement experiences. They focus on the contralateral or ipsilateral aspects of the human body in regards to lower limb and upper limb dominance and combinations during fine and gross motor movements (Ziyagil, M. 2011). Foot preferences and hand preferences occur at different stages of development but both are apparent in all adults, and are often demonstrated in daily life.

History

All adults use one hand preferentially and usually more proficiently on tasks requiring speed, precision, force, skill, and especially coordinated sequences of movements. Hand preferences have existed as long as humans and were considered to be a necessary distinction before complex human language and fine motor functions developed. (Gutwinski, 2011). Throughout history, individuals who were left-handed were stigmatized and discriminated against and were described by phrases such as “gauche” which implies clumsiness and awkwardness (Gutwinski, 2011) and was also associated with mental deficiency and behavioral and emotional problems (Barr et al. 2005). In addition, individuals who were left-handed were considered to have poor coordination and motor skills. However, this could partially be due to the fact that objects and environments were created that were easier for the majority of individuals who were right-handed (Tan, 1985). For the same reason, individuals who are not right-handed tend to be at a higher risk for accidents (Gutwinski, 2011). Despite these disadvantages, there is an unusually high proportion of high-performance athletes who are left-handed, as their differences may in fact provide them with a tactical benefit. Hand preferences are apparent in tasks such as writing, drawing, throwing, using utensils, opening jars and using tools. The ‘dominant’ hand can work alone, but depending on the task, the other hand usually plays a supporting role (Barr et al., 2005). Footedness is having a preference of a dominant foot for certain motor situations and can vary depending on the motor skill. For example, in a kicking motion one foot acts as a stabilizer (the one on the ground) while one foot acts as a mobilizer (the kicking foot). Because of the variability of footedness, there is no history of biases towards left-footed individuals but there is more of a likeliness of left handed individuals to be left footed.

Motor Asymmetries in the Population

Handedness

Humans have been divided into ‘left-handers’ and ‘right-handers’, which make up 10-15 and 85-90 percent of the population respectively. The classification of handedness has been shown to be on a continuum, however, including ‘mixed-handed’, ‘weak right or left handed’, or true ‘ambidexterity’ which is very rare. Left-handers are also more variable in their proficiencies and preferences based on tasks and are more inconsistent in their dominant hand use. Left-handedness is also more common in males than females and the chances of being left handed are 25 percent when both parents are left-handed, and 10 percent when neither are left handed (Barr et al. 2005).

Footedness

There is a much less bias towards foot preference as there is for hand preference in the population. For example, 13 percent of 16-19 year olds reported they were equally adept with both feet, where 6-7 percent of the same group reported being adept with both hands. This could be connected to the amount of time hands are engaged in movements that require role differentiation where it matters more as to what hand does what in order to perform well than it does for everyday foot use. Also in sports, foot preference often has to mirror or accommodate what the hands do, and therefore must be more flexible (Peters, M. 1988). In a study regarding pure and mixed handedness in relation to foot preference, where pure handers are those that choose the dominant hand for all items on a handedness questionnaire, and mixed handers declare some non-dominant hand preference, it was found that 96 percent of pure right-handers and 87 percent of the mixed right-handers preferred the right foot for kicking (Peters, M. 1988). 83 percent of the pure left-handers preferred the left foot, where only 52 percent of the mixed preferred the left. There are much fewer pure left-handers than mixed so as a group they do not show a strong foot preference. Data has varied but the majority has shown that left-handers have a lower prevalence of foot preference. There could be some cultural bias towards this result as there is against left-handedness as well. Studies have also shown that when starting a stride, the majority of people, even children will start with the left foot. This could be explained by the statistics of more left and right handers being right footed, therefore having more stability in their right foot, hence leaving it on the ground first for balance (Peters, M 1988). However, when lifting a pebble when standing, 75 percent of right-handers preferred the right foot, while only 13 percent of left-handers did. Other studies show that when sitting cross-legged, more people have their right leg on top and more children are likely to lead with their right foot when sliding on ice, due to it’s preference when bearing more weight.

Foot and Hand Correlations

When hands and feet function together, they can interact contralaterally or ipsilaterally. For example, when throwing a ball, if using the right hand, a thrower will step with their left foot first to balance the movement, which is contralateral. In contrast, a motorcycle driver will gear and gas with one side of the body and clutch and break with the other using ipsilateral motions (Peters, M. 1988). The right foot tends to be the preferred foot for right-handers in cases where the foot is used for manipulation or precision, while left foot preference is more inconsistent, much like it is in hand preference. Right handers show much more laterality in that they are more likely to be right footed, whereas left handers are much more variable in their footedness. Laterality in the hands and feet could have some impact on performance in activities where the right and left sides must act together, such as driving a motorcycle, but rarely impact an individuals’ daily life or skill performance (Peters, M. 1988).

Development of Motor Asymmetry

Handedness

Just as infants and children vary in their motor development, they also vary in their development of handedness, with left-handers showing less consistency in their early hand dominance. Studies have shown that fetuses in the womb show hand biases as early as 10 weeks, demonstrated by 54 out of 72 fetuses making more right arm movements, and at 15 weeks more of a tendency to suck the right thumb (Barr et al. 2005).

In newborn infants, the majority will illicit pre-reaching movements (swiping) with their right arm as well as elicit a stronger grasp with their right hand, and will also lie with their head to the right when on their back. By 4 months infants show directed reaching and gradually will show a hand preference by 10 months, in which one hand will make contact first or is used predominantly. They also show differences in movement quality such as shorter movement times and fewer errors with their dominant hand at around 8 months. From 13-24 months infants show an increase in hand differentiation when performing tasks that require two hands. For example when using a nut and bolt toy they will turn the bolt with their dominant hand and hold the nut with the other. From 2-6 years children will have developed a strong hand preference, and it is visible in such complex skilled tasks such as using scissors, printing and throwing.

Handedness is also determined to be stable and fixed as early as 3 years, and degrees of handedness can increase up until approximately age 7 (Barr et al. 2005). Infants do however, demonstrate a shift between left and right several times before acquiring a stable preferred hand and preferences also fluctuate during the development of major milestones. For example, when learning how to walk at the age of about 11 months, hand preferences were shown to be less stable, but there was also an increase in foot preference at this time. The patterns of foot or hand preference during infancy reveals the interconnectedness of the motor system and how upper and lower limbs reflect one another to an extent. Another theory as to why right-hand preference decreases at this age is that it is also during this time that language milestones are met, thus greater demands being placed on the left hemisphere of the brain, reducing the amount of attentional control available for motor behavior (Berger, S. et al, 2011).

Footedness

When studying infants, no significant biases were found regarding the stepping and kicking reflexes and data that was found was inconsistent across ages of infants. This could be due to reflex pathways maturing at different rates in the infants’ nervous systems. There was however, more leg movements in the direction on the side of the preferred head direction of the tonic neck reflex (Peters, M. 1988). Also, the development of handedness differs in acquisition time to footedness due to experience differences in reaching and locomotion, in that infants learn to reach several months before they can crawl (Berger, S. 2011). Foot dominance is quite variable in infancy and childhood, and data has shown a strong right-footed preference by age 4, which strengthens through age 11. In children from 3-11 years of age, 30 percent are mixed-footed when compared to adolescents and adults, who only 19 percent were mixed-footed. The difference in these percentages is also most likely those individuals who eventually became right-footed, which is shown to be the much more common foot preference in adults (Gentry, V. et al, 2001). Foot specialization is more unbiased because activities that require the use of feet are usually less complex and practiced and are also less subject to social pressure than handedness. Also the experience factors that strengthen the degree of hand preference during childhood may be less of an influence on foot preference (Gentry, V. et al, 2001).

Theories of Asymmetry

Biological

It has been proposed that handedness reflects structural/physiological asymmetries in the brain regions responsible for motor control. The spinal cord, cerebellum, basal ganglia, and cerebral cortex are all thought to contribute, with different mechanisms more relevant for certain features and developmental periods. There is also a connection between handedness and speech control, with 95 percent of right handers being left-dominant for speech, whereas only 66 percent of left handers are being left-dominant while the remaining are right dominant or bilateral. There is also a genetic explanation that there is a dominant allele that predisposes the left-hemisphere control of speech and right-handedness, whereas individuals with the recessive allele lack this predisposition and the side control of both functions is left to chance, with equal chances to be left or right dominant (Barr et al. 2005). Another theory suggests that humans are said to be pre-disposed to be right handed and footed, and left-handers preferences are therefore left to chance, thus resulting in more variability (Peters, M. 1988).

Foot biases have also been shown to correlate with hand biases to a certain degree. Right-handers who are right foot dominant show a right-foot bias for activities requiring fine manipulation, whereas the left leg is preferred for support and power functions. In addition, the left leg tends to be longer and heavier than the right in most people. For example, in sprinters, left-handed subjects had stronger left legs than right, whereas right-handed sprinters leg strength did not differ, supporting the fact that their right leg, even though dominant in dexterity, was not physically more muscular than the left (Ziyagil, M. 2011). It was also found that movements requiring speed and precision were initiated by the left leg (dominant in most people who are right handed), and movements requiring strength were initiated by the left leg. Also, the right arm in right-handers is longer than the left arm as early as age 6, and the left leg begins to show more length in the early teens (Ziyagil, M. 2011).

Environmental

One environmental theory of motor asymmetry is the uterus explanation, which suggests that a fetuses position in utero contributes to their handedness, resulting from more mobility with one hand or what way their head is turned. In addition, a sociocultural explanation suggests that the role of education, socialization and culture is significant in determining a child’s handedness. For example, left-handedness was discouraged in the past, resulting in less prevalence of it among the elderly. The prevalence of right-handed objects is clear today, from tools such as scissors and can openers to musical instruments and school desks. Also, functional demonstrations and instructions from parents, peers, and teachers can have an impact on development with regards to new skills and movements are introduced to children (Barr et al. 2005).

Conclusion of Theories

No single explanation can account for all of the features of handedness. A wide variety of mechanisms is said to operate and have varying degrees of influence on hand dominance depending on features and time periods. The degree of contribution that genetics, the nervous system and environment play on handedness is unknown but can be more understood with further research. For example, the role of education could be looked into further, in that it may have an effect on the degree of students’ handedness. This could even happen before a child enters school, for example, determining the effects of when a parent places an object in their child’s hand, or demonstrates a movement with a preferred side. This could also be variable depending on whether the parent’s behavior is planned or in response to cues from the child (Barr et al. 2005).

Motor Asymmetry in Sports

Hand and Foot Selection

The choice of the arm often determines the role of the feet in sports. For example, in throwing sports the foot used in the final phase of throwing is determined by the arm used. For example, a right-handed boxer will have their left food forward and a pole-vaulter will propel their body with the opposite foot of their leading arm. High jumpers prefer their left foot as the foot that provides the thrust, preferring the dominant leg to lead over the bar. In contrast, long jumpers need to consider the particular placement of their thrusting foot, but they also want to lead with a strong foot too, so there is more compromise between foot preference. This is also similar to long jumpers and hurdlers, who must carefully choose which foot to consistently lead with. It is also argued that those athletes with crossed hand-foot preference are at an advantage due to the fact that compensatory movements made by the contralateral upper limb are the sorts of movements that are done best by the preferred upper limb (Peters, M. 1988).

Right or Left Advantages

Where there are overall more right-handed top athletes, there is a higher proportion of left-handers among top athletes in sports such as baseball, tennis, fencing, cricket, and combative sports such as boxing and wrestling. This shows that the advantage of left-handedness depends on the sport, and is in relation to their adaptability to opponents and the unexpectedness of the left-handed athletes’ movements. For example, in boxing a left-hander feels they have an advantage because they have greater experience fighting right-handers than right-handers have in fighting left-handers (Peters, M. 1988). Studies have also shown that left-handed soccer players were more comfortable kicking with both feet, and left-footed soccer players, when maneuvering against a right-footed opponent can keep their body more between the ball and the defender. Also, a player who can kick a penalty shot with both feet is at a significant advantage (Peters, M. 1988). Moreover, the advantages of handedness and footedness can contrast within sports. For example, in sprinters, left-handed participants had slower running speeds when compared to right-handed sprinters but no speed difference was observed in left or right-footed sprinters (Ziyagil, M. 2011).

Right-handers tend to have an advantage in response and movement times, whereas left-handers have an advantage in reaction times. For example, sprinters tend to be faster when they start with their right hand and foot (Ziyagil, M. 2011). This could be explained by the findings that the right hemisphere of the brain is generally associated with spontaneous and automatic responses, while the left hemisphere is mostly responsible for logical, controlled, and deliberate thoughts and actions, performing after planning. Thus, reaction time as a spontaneous and automatic response would be better in left handers, being controlled by the right hemisphere of the brain and gross motor movement tasks would be more associated with right-handedness.

Recommendations for Parents and Practitioners

If child is demonstrating left-handedness, there are lots of products that are made for use by left-handed individuals. Stores such as Lefty’s in San Francisco have a wide range of products, from watches to school supplies, that are designed with a left-handed consumer in mind.
If a movement looks odd, do not immediately discount it as a bad motor pattern. It may look odd because it is mirrored. Look at the end result of the movement and whether it is successful or not.
Children without a preferred hand may serve as a marker for requiring special assistance with motor skill development so they should be identified and assisted as needed (Tan, 1985)
When writing, let the child play around with handgrips. If an unconventional writing style allows them to write quickly, relatively legibly and for long periods of time, don’t try to change it. (Peachey, 2004).
If classrooms or other study spaces have chairs with built-in half desks, make sure that there are sufficient left-handed desks. Having to twist to use a desk with the desk on the right of the chair can result in poor posture and cramped and slow writing.
If a left-handed child seems clumsier than others, take a look at the environment. It may be set up so that it is easy for right-handed individuals to navigate at the expense of left-handed individuals.
There are a lot of web resources that discuss handedness. Some are better than others, but websites such as http://www.indiana.edu/~primate/lspeak.html provide insight into what being a left-handed or ambidextrous individual can mean and provides additional tips to try. Not all of the advice will work for all individuals, but they can help with teaching non-right-handed individuals.
Motor asymmetries can be of important use when determining developmental issues in children. For example, when examining gait problems in children with motor delays it is effective to know what their foot or hand preferences are.

Development

When considering development and instructing children learning a new task, it could be useful to follow these principles.

1. In the design of foot controls, the preferred foot should perform the actions that are more directly related to the goal of movement, and the non-preferred foot should, whenever possible, be assigned supportive movements. 2. Where hands and feet collaborate, complementary roles should be assigned to the hand and foot on the same side. 3. If operations can be subdivided in terms of a hierarchy of complexity and the degree to which the movement is directly attended to, foot actions should be given a role subordinate to that of hand actions whenever the question of assigning a subordinate role to hand or foot arises. 4. For almost all right-handers, the preferred foot is the right foot. Left-handers, if they do not already have foot preference patterns similar to those of right-handers, appear to adapt quite readily to the arrangement that is suitable for right-handers.

(Peters, M. 1988)

Sport Training

In early childhood children are still developing their gross and fine motor skills and specific training in regards to improving athletic skills is not extremely crucial. The prepubescent period is a more critical time of development when athletes require more appropriate and specific training. Handedness and footedness should be considered in individual training programs during pre-puberty and new training methods are recommended that can improve strength in the weaker arm or leg to promote more symmetry. Also, an understanding of speed ability in prepubertal children with respect to hand and foot preferences could assist in diagnosing deficiencies related to locomotor speed and resolve problems during the developmental period where correction is most effective (Ziyagil, M. 2011). Practice is recommended for all athletes, especially in those sports where motor asymmetry could cause a disadvantage. For example, it is more common for dancers to show a weaker left foot, and they are commonly required to practice twice as much regarding left leg maneuvers (Peters, M. 1988).

References

Barr, R., Rochat, P., Michel, G. (2005). Handedness. The Cambridge Encyclopedia of Child Development. (Vol. 1, pp. 321-326). Cambridge, UK: Cambridge University Press.

Berger, S. et al. (2011). The role of locomotor posture and experience on handedness and footedness in infancy. Infancy and Development.

Gentry V. et al. (2001). Foot-Preference Behavior: A Developmental Perspective. The Journal of General Psychology, 122(1), 37-45.

Gutwinski, S., Loscher, A., Mahler, L., Kalbitzer, J., Heinz, A., & Bermpohl, F. (2011). Understanding left-handedness. Deutsches Arztebl International, 108(50), 849-853.

Johnston, D.W. et al. 2009. Nature’s Experiment? Handedness and Early Childhood Development. Demography; 46(2): 281–301.

Peters, M. 1988. Footedness: Asymmetries in foot preference and skill and neuropsychological assessment of foot movement. Psychological Bulletin, Vol 103(2), 179-192.

Tan, L. E. (1985). Laterality and motor skills in four-year-olds. Child Development, 56(1), 119-124.

Ziyagil, M. A. 2011. Handedness and Footedness: Relations to Differences in Sprinting Speed and Multiple Sprints Performance in Prepubertal Boys. Perceptual and Motor Skills 112, 2, 440-450.