- Motor development is a biologically driven process and follows the pattern of the child's brain growth and development. This pattern results in the development of motor skills in a cephalo-caudal, proximo-distal fashion. This means that the infant/toddler gains motor control over her muscles starting from the head, and moving down the spine, and from areas close to the spine to areas further away from the spine.
- The specific age at which each of the motor milestones is acquired is variable and therefore less meaningful than the PATTERN of motor development shown by a child.
- Motor development can be seen as the nexus for development, out of which other developmental skills can spring. As motor skills are acquired, the infant or child becomes more aware of his own body and his environment, can create new motor skills by linking skills acquired earlier with skills acquired more recently, and can acquire other developmental skills, such as new cognitive insights and more language. Of course, the converse is also true. The acquisition of more sophisticated motor skills can also be the result of the acquisition of language and cognitive skills.
- Biological patterns of motor development are most apparent during the first year. After the first year, motor skills are determined much more by a combination of biology and external factors. These include culture, experience, health, and environment.
Major Factors in the Acquisition of Motor Skills
- Postural control is an important component of motor development, without which controlled movements are not possible.
- Awareness. The infant becomes aware of his or her movements, and learns to take pleasure from them. Pleasure is derived from both the movements themselves, and from the effect that the movements can have on the environment.
- Linking. Complex physical skills are created by linking simpler movements. Infants start out by learning basic movements or postures such as sitting, standing, walking. At the same time, they couple these basic skills with reaching and grasping, for example. From here, things only get better: running, throwing, and more complex arm and leg movements. Without the basic movements or postures in place, however, the more complex skills are not possible or are compromised.
- Acquisition of other developmental skills. As more complex movements become possible, the infant and child is able to develop other developmental skills such as language, cognition, and social-emotional skills. In turn, the acquisition of these other developmental skills allows for the acquisition of more complex motor skills.
Gravity and the Early Development of Movements
Many of the earliest activities of infants are concerned with achieving and holding stable postures against the influence of gravity. Initially, these occur through the primitive reflexes which are important to help maintain the infant's posture.
With neurological maturation (myelination of neurons and increase in number of dendritic connections in the central nervous system [CNS]), the infant takes over postural control voluntarily. Further, as this maturation occurs, the reflexes are suppressed which opens up the possibility for new movements to develop.
In normal children, the achievement of basic abilities as sitting, standing or walking is seen to occur in a cephalo-caudal and proximo-distal fashion, which reflects the sequence of neurological maturation mentioned above.
The Effects of Impaired Movement
Motor activity is important for linking together developmental progress in the other developmental spheres (speech/language, cognition, and socio-emotional). A child with limited motor skills or a limited capacity to move will be usually be exposed to developmentally-enriching experiences less often, and will thus develop other perceptual skills more slowly. Thus, motor impairments can limit overall development.
Children who cannot move normally show higher levels of frustration, dependence, and lack of social interactions. A five year old child who cannot tie his shoelaces or an adolescent who feels physically inadequate can show more hostile reactions to parents, siblings, and peers. A child with spina bifida (a defect in the embryologic development of the lower spine and spinal cord) who cannot use his legs has a more limited experience of the world because he is not able to explore it as successfully. He expends more energy maintaining postural control using other muscles such as his arms and hands. Furthermore, he has less opportunity for linking, such as learning to use his arms or developing fine motor (hand) skills because he has to use his arms and hands as supports for moving around, depriving him of the opportunity to refine hand movements for other purposes. Finally, his motor impairments can interfere with the acquisition of other developmental skills, because he does not have the same opportunities to explore the environment, create social interactions, etc.
The Primitive Reflexes
The primitive reflexes are concerned with postural control. As we will see, postural control becomes a voluntary process once the infant/toddler develops control over the muscles that maintain posture.
- The placing reflex. Present from birth until about 6 weeks. Stroke the dorsal aspect (upper side) of the infant’s foot. The infant will lift that foot and place it on the surface nearby.
- The asymmetric tonic neck reflex. Present from birth until about 2 months. With the infant lying supine (on his back), turn the head on one direction. The contralateral arm (the arm opposite the side that the infant is facing) will flex. The ipsilateral arm (the arm on the same side of the direction in which the infant is facing) will extend.
- Moro response. Present from birth until age four months. The infant is lying supine, and lifted by his arms a few inches off the mattress, and then dropped. The arms first move briskly back, then move forward, and the infant cries.
- Parachute reaction. Emerges at age 8 to 9 months. The infant is held a few inches above the mattress or floor in ventral suspension, and then partially dropped towards the floor. The arms extend to protect the fall.
A Look at Motor Development in the First Year
Motor development can be understood to occur along three axes:
- prone/ventral suspension
- vertical (standing)
Breaking the developmental sequence down into these three axes is helpful in understanding the variability that can be seen in the acquisition of motor milestones in any given infant. Although the sequence of development is very predictable within any one axis, the three axes may be developing at somewhat different rates.
Thus, for example, a child may learn to sit and crawl (to move on the ground using the elbows, powered by the shoulder and upper arm muscles, with the rest of the body lying flat on the floor) while waiting to learn how to creep (move on hands and knees) or stand later. Another child may learn to sit and then stand, learning to creep afterwards. What is happening here is that the first child has developed sitting skills (lower spine and abdominal muscle control) and upper limb skills (shoulder and upper arm control) before acquiring lower extremity motor skills (hip and leg muscle control). The second child has learned to sit and then stand (hip and leg muscle control) without ever crawling. Her lower limb strength was such that she was able to move directly to standing. This is a simplified explanation of the different muscles needed for these basic movements, but serves to illustrate some of the variability seen in infant motor development.
Gross Motor Developmental Milestones in the First Year
The following breakdown helps to understand the sequence of events in the acquisition of gross motor milestones in infancy. Pictures during the lecture serve to illustrate these milestones.
Supine /pulled to sitting:
The infant lies on her back, and the examiner lifts her upwards using her hands. This sequence is illustrated by the slides shown during the lecture. Note the cephalocaudal progression:
- Newborn held in sitting position: complete head lag
- 12 weeks (3 months): slight head lag.
- 20 weeks (4 to 5 months): no head lag. 24 weeks (5 to 6 months) sits supporting self.
- 28 weeks (6 to 7 months): sits without support
- 40-44 weeks (10 to 11 months): good support while sitting and able to perform various movements.
- 15 months: sits in a chair
The infant is held in ventral suspension (stomach horizontal to the floor), allowing for the illustration of proximo-distal muscle development. Again, this starts at the level of the head and neck. Only later is the lower body engaged in this same pattern of proximal to distal. You will notice that some of the milestones described here overlap with those discussed above. The milestones are illustrated in the lecture slides.
- Newborn held in ventral suspension: lack of head control
- 6 weeks: momentarily holds head in same plane as rest of body.
- 8 weeks: maintains head in line with body
- 12 weeks (3 months): maintains head above line of body. Now able to hold the chin and shoulders off the couch.
24 weeks (5 to 6 months): keeps the chest and shoulders off the mattress, maintaining his weight with his hands and with extended elbows.
- 12 weeks (3 months): rolls from prone to supine 4 months rolls supine to prone.
- 8 to 9 months: crawl. Crawling requires hip and upper leg muscle control. The infant is now able to lift his entire trunk off the floor.
Standing and walking
This sequence is illustrated by holding the infant or toddler in a standing or vertical position.
- 2 months: holds her head up momentarily.
- 6 months: the infant can bear almost all her weight, using her legs as pillars.
- 9 months: she stands holding on to furniture and can pull herself up to the standing position.
- 11 months: she is seen to lift one foot off the ground.
- 12 months: she walks with a broad base and steps of unequal direction and length.
- 15 months: she crawls upstairs and can get into the standing position without help.
- 18 months: she can get up and down stairs without help and pulls a doll or wheeled toy along the ground.
- 2 years: she can pick an object up without falling, can run forwards and walk backwards. She goes up and down stairs with two feet per step.
- 3 years: she can stand for a few seconds on one leg. She goes up stairs one foot per step, and down stairs two feet per step. She can ride a tricycle.
- 4 years: she goes down stairs one foot per step and can skip on one foot. At 6 she can skip on both feet.
Early motor development can be broken down into supine-prone-upright sequences. When the infant and toddler is held or seen in these different positions, the cephalo-caudal, proximo-distal sequence of motor milestone acquisition is apparent.
The two goals of gross motor skills in the first year are the attainment of a stable posture in the standing position, and the achievement of walking. Although the environment plays a role in the first year, it becomes much more important beyond the first year. Environmental stimulation allows for the acquisition of more complex motor skills.
Fine Motor Development in the First Year
Fine motor skills pertain to the manipulation of objects. A pincer grasp is what is ultimately needed for good fine motor control. These skills are then linked with visuo-spatial skills, which are both motor and cognitive skills.
- 1 month: hands mostly closed
- 2 months: grasp reflex
- 3 months: hands mostly open
- 4 months: hands come together, overriding the asymmetric tonic neck reflex (ATNR).
- 4-5 months: Child can start to learn about an object through inspection (visual and oral).
- At 5 months: grasps an object voluntarily.
- 6 months: two hands may come together; transfers Thereafter his grasp has to go through several stages: ulnar grasp, radial grasp, finger thumb (pincer) grasp
- 10 months: early finger-thumb grasp: can let go of objects (casting)
- 12 months: mature pincer grasp
- 13 months: builds a tower of two 1" cubes
- 15 months: picks up a cup, drinks from it, and puts it down without much spilling.
- 18 months: he turns 2 or 3 pages of a book at a time
- 2 years: turns pages singly; can put on socks.
- 2.5 years: threads beads
- 3 years: fastens buttons, dresses and undresses self.
Gross Motor Skills Beyond Age One
The skills described above (standing, walking, and pincer grasp) are the basic building blocks of more complex motor sequences. These motor skills are inextricably linked with, and assist in the acquisition of, other developmental skills. The following components describe linking and acquisition of developmental skills.
The toddler and child:
- Can link basic movements with one another. Walking while pulling a toy, sitting while using utensils to eat, etc.
- Can control the speed, strength, sequence, and timing of motor skills
- Becomes aware of individual tasks and the pleasure or displeasure it brings
- Can select what movement to produce
- Can choose whether or not to act.
A selection of common gross motor skills of early childhood:
- 2.5 years: walking on tiptoe
- 2.5 years: walking along a straight line
- 3 years: walking along a circular line
- 4.5 years: walking heel-toe
- 2.5 years: going up without support, alternating feet
- 4 years: going down, without support, alternating feet
One leg skills
- 3 years: stands on one leg for 2-3 seconds
- 3 to 5 years: increasing length of time on one leg
- 4 years: hopping on the spot 5 times
- 5 years: hopping on the spot 10 times