MOTOR DEVELOPMENT

When babies are born, they are not able to move much on their own. Over time, a baby learns to move many parts of its body and control its muscles so it can hold its head up, sit up by itself, stand up, or pick up a toy. The process of motor development, however, does not happen overnight. Like many things, learning about the body and making it move takes time. Motor development is the process of learning how to use muscles in the body to move. The progression of acquiring motor skills goes from simple to complex.

Motor development happens in a predictable sequence of events for most children, but each child varies in age when each skill is mastered. For example, although most children begin to walk independently around twelve to fourteen months, some children are walking as early as nine months. Further, children differ in terms of the length of time it takes to develop certain motor skills, such as the baby who sits up, virtually skips crawling, and begins walking.

Transition from Reflex Movement to Voluntary Movement

At birth, babies have very little control over their bodies. They spend most of their time curled up in what is called a fetal position. This position is how the baby lay in the womb during the nine months of the mother's pregnancy. In addition to the fetal position, primitive reflexes dominate virtually all of a newborn baby's movements. Babies are born with these reflexive movements as a means for basic life preservation. The reflexes, which are controlled by lower levels of the brain, eventually give way to more sophisticated voluntary movements monitored by higher levels of the brain.

The first voluntary task of a newborn is learning to bring the arms and legs out straight in order to lie flat. This maneuver takes a lot of muscular energy, so the baby begins moving arms and legs around during the waking hours to develop coordination and strength. As babies move their bodies more in the first months of life, motor pathways begin to form in the brain. These pathways allow a baby to eventually perform motor movements without conscious thought.

Principles of Development

The process of motor development depends heavily on the maturation of the central nervous system and the muscular system. As these systems develop, an infant's ability to move progresses. The sequence of motor development follows an apparently orderly pattern. Arnold Gesell, a noted researcher in the field of child development, indicated through his studies that development does not proceed in a straight line. Instead, it swings back and forth between periods of rapid and slower maturation. Gesell and his colleagues also discovered from their infant observations made in the 1930s and 1940s that infant growth does indeed follow distinct developmental directions: cephalocaudal, proximal-distal, and general to specific.

Cephalocaudal Principle

First, most children develop from head to toe, or cephalocaudal. Initially, the head is disproportionately larger than the other parts of the infant's body. The cephalocaudal theory states that muscular control develops from the head downward: first the neck, then the upper body and the arms, then the lower trunk and the legs. Motor development from birth to six months of age includes initial head and neck control, then hand movements and eye-hand coordination, followed by preliminary upper body control. The subsequent six months of life include important stages in learning to control the trunk, arms, and legs for skills such as sitting, crawling, standing, and walking.

Proximal-Distal Principle

Second, children develop their motor skills from the center of their bodies outward, near to far or proximal-distal. This principle asserts that the head and trunk develop before the arms and legs, and the arms and legs before the fingers and toes. Babies learn to master control of upper arms and upper legs, then forearms and legs, then their hands and feet, and finally fingers and toes. An example of this is an infant's need to control the arm against gravity before being able to reach for a toy.

General to Specific Principle

Lastly, the general to specific development pattern is the progression from the entire use of the body to the use of specific body parts. This pattern can be best seen through the learned process of grasping. Initially, infants can grossly hold a bottle with both hands at about four months of age. After practice and time, twelve-month-old infants can hold smaller toys or food in each hand using a pincher grasp. This finger and thumb grasp is more precise than the grasping skill of an infant at four months. Just as the child develops a more precise grasp with time and experience, many other motor skills are achieved simultaneously throughout motor development. Each important skill mastered by an infant is considered a motor milestone.

Motor Milestones

Motor milestones are defined as the major developmental tasks of a period that depend on movement by the muscles. Examples of motor milestones include the first time a baby sits alone, takes a step, holds a toy, rolls, crawls, or walks. As discussed previously, the timing of the accomplishment of each motor milestone will vary with each child. "Motor milestones depend on genetic factors, how the mother and father progressed through their own development, maturation of the central nervous system, skeletal and bone growth, nutrition, environmental space, physical health, stimulation, freedom and mental health" (Freiberg 1987; Paplia and Wendkosolds 1987). Within the motor milestones exist two forms of motor development: gross motor development and fine motor development. These two areas of motor development allow an infant to progress from being helpless and completely dependent to being an independently mobile child.

Gross Motor Development

Gross motor development involves skills that require the coordination of the large muscle groups of the body, such as the arms, legs, and trunk. Examples of gross motor skills include sitting, walking, rolling, standing, and much more (see the list of gross motor milestones in Table 1). The infant's gross motor activity is developed from movements that began while in the womb and from the maturation of reflex behavior. With experience, the infant slowly learns head control, then torso or trunk control, and then is rolling, sitting, and eventually walking. The first year of a baby's life is filled with major motor milestones that are mastered quickly when compared to the motor milestone achievements of the rest of the baby's development. In addition to the development of gross motor skills, a baby is simultaneously learning fine motor skills.

Fine Motor Development

Fine motor development is concerned with the coordination of the smaller muscles of the body, including the hands and face. Examples of fine motor skills include holding a pencil to write, buttoning a shirt, and turning pages of a book (see the list of fine motor milestones in Table 1). Fine motor skills use the small muscles of both the hands and the eyes for performance. For the first few months, babies spend a majority of time using their eyes rather than their hands to explore their environment. The grasping reflex, which is present at birth, is seen when a finger is pressed into the baby's palm; the baby's fingers will automatically curl around the person's finger. This grasping reflex slowly integrates and allows the development of more mature grasping patterns. At four months, babies will begin to more frequently reach out for toys with their arms and hands. The reach looks more like a swipe because the baby is learning how to control the arm and hand. Over time, babies learn how to make smoother and coordinated movements with their arms and hands.

Assessment of Gross Motor and Fine Motor Development

Many assessment tools exist to measure a child's performance in regard to gross and fine motor skills. Each assessment requires good observational skills from the evaluator, who is typically a developmental pediatrician, nurse, educator, occupational therapist, or physical therapist. Some assessments call for each item to be administered in a formal standardized manner, so that each child is tested the same way every time. These tests are also called normative-based because they compare individual performance to that of other children. Other measures encourage professionals to ask parents questions about their child and are based on informal observations of the child at play. These more informal tests are referred to as criterion-based assessments because they compare individual performance to a criterion or standard. Regardless of the type of assessment, each measure has the common purpose of evaluating the child's current ability to perform motor-related tasks. Professionals use the results of these assessments to decide whether intervention is needed and also to guide goal setting and outcome measurement.

Delays in Gross Motor and Fine Motor Development

When children are not able to perform the motor skills at the appropriate milestones, their motor development may need to be evaluated by a professional. When motor skills do not progress along a normal trend, a child may be at risk for missing out on potential learning and social experiences. Children who demonstrate potential motor delays are at risk for continuing these delays throughout later development. For example, a child who demonstrates weak hand strength and has difficulty coordinating finger movement may have trouble with handwriting in school.

Early Intervention

After 1986, legislation was passed at the state level to set up services that assist families who suspect their child may have some developmental delays. These services are called early intervention systems. The main purpose of early intervention is to offer evaluation and treatment to children from birth to age three and to their families. The professionals involved with early intervention are members of a team who test a child's skills to see where the child's current skills are in relation to the chronological age. Children who are not doing many motor activities typical of their age may be considered at risk or delayed. These children may not have the strength, coordination, or balance to do most things that others of their age can do. The professionals involved in early intervention include occupational therapists, physical therapists, speech language pathologists, special education teachers, nurses, doctors, social workers, and service coordinators. Each of these professionals help the child and family learn about ways to improve motor coordination so the child can function more independently.

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Joan ZieglerDelahunt