Development of Motor Control in Children and Adolescents
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In everyday life, we use thousands of movements to navigate through our world. Rarely do we take the time to analyze where these movements come from, or how they are executed on a neuromotor level. Perhaps even less often do we contemplate how these movements have changed with age. Any mother can certainly tell you that she expects to aid her infant by holding its bottle during feeding at first. However, at one year of age, that same mother would certainly show serious concern if her child could not yet hold a bottle on its own. Motor development (consisting of similar reach-to-grasp movements, goal-directed movements, proprioceptive sensitivity, and even neuromotor development in general) continues to develop throughout childhood and adolescence. Several studies have been done to evaluate at what age certain abilities develop, and also at what age they improve in accuracy.
In a study by Largo, Caflisch and Hug (2001), children between the ages of 5 and 18 years were timed during 10 distinct motor tasks of varying difficulty to test developmental
course and inter-individual variation. 477 children were recruited in kindergarten, first, third, and sixth grade in the city of ZÑŒrich. The school classes were randomly chosen and all children recruited were initially included. The majority of the children lived in the ZÑŒrich area and
came from families with middle-class characteristics. Their mean socioeconomic status was significantly higher than that of the general population. Children wore a minimum of clothing and rubber-soled socks or were barefoot. They sat in a chair facing the examiner, and were instructed to bring their legs into a position where hip, knee, and ankle joints are flexed at a 90o angle. For each task, the examiner gave verbal instructions while demonstrating the expected performance to ensure that the child understood the instruction. The time needed to perform the required number of movements was recorded for the following six motor tasks: (1) Repetitive finger movements (20 taps between index finger and thumb). (2) Repetitive hand movements (20 pattings of one hand with the wrists resting on the thighs and the palm of the inactive hand held down). (3) Repetitive foot movements (20 taps of the forefoot while the heel of the foot remains on the floor). (4) Alternating hand pronation-supination (10 pairs of alternating movements of
one hand with the wrists resting on the thighs and the palm of the inactive hand held up). (5) Alternating foot movements (10 pairs of heel-toe alternations in a rocking motion. (6) Sequential finger movements (opposing each finger with the thumb in sequence). Children younger than 7 years performed three sets; older than 7 years, five sets. The stopwatch was not started by the examiner on the word go, but on the third tap, the second set, or the second alternating pair for each task, and stopped at the conclusion of the required number of movements.
The researchers found that timed performance of all motor tasks improved steadily
throughout the entire prepubertal period. However, the annual increase in speed differed considerably among motor tasks. Between 7 and 18 years, time for repetitive finger movements decreased from 6.2 to 4.2 s, while the sequential finger movements did so from 14 to 5.5 s. Timed performance of the various motor tasks also reached a plateau at different ages during adolescence. Repetitive movements leveled off at 15 years, and alternating movements did so at 18 years, while sequential movements had not quite reached a plateau by 18 years. The increase in speed differed considerably and appeared to be a function of the complexity of the movement pattern. Repetitive movements improved less than alternating and sequential movements. The age at which a specific motor task reached a plateau seemed also to be related to the complexity of the movement pattern. Repetitive movements leveled off as early as 12 to 15 years, while alternating and sequential movements improved up to the age of 18 years.
Such results may make one wonder if there was any difference between females and males, or even between left-handed and right-handed individuals. Since females are thought to mature faster biologically, the researchers could have tested if that was also the case with nueromotor development. They could have done this by blocking groups into males and females, instead of having co-ed groups of the same age. Also, right-handed individuals are thought to be more accurate in handwriting and fine motor tasks. The researchers could have also blocked groups into right and left-handed children.
In a study by Kuhtz-Buschbeck, Stolze and Boczek-Funcke (1998), the researchers wanted to learn about the normal development of functional hand motor skill (prehension movements). 54 healthy children (age 4-12 years) subjects repeatedly reached out for cylindrical target objects and grasped them with a precision grip of their dominant hand. The trajectory of the reaching hand and the finger aperture were monitored by optoelectronic motion analysis. The results showed that neither the movement duration nor the normalized peak spatial velocity of the reaching hand changed significantly. However, the hand trajectory straightened and the coordination between hand transport and grip formation improved, resulting in smooth and stereotyped kinematic profiles at the age of 12 years. The younger children opened their
grip relatively wider than the older ones, thus grasping with a higher safety margin. The dependence on visual control of the movement declined during motor development. Only the oldest children
were able to scale the grip aperture