Infant Development in Supine

Original Editor - Pam Versfeld

Top Contributors - Stacy Schiurring and Jess Bell  

Introduction

This article describes infant motor development when lying supine on a firm flat surface. In the article development in supine is divided into 4 periods: (1) newborn infant, (2) infant from 1-2 months, (3) infant from 3-4 months and (4) infant from 5-6 months.

Time lying supine on a firm flat surface is important because it is the first position that allows infants to independently interact with their environment and learn how to stabilise head and trunk which in turn allows them to use their vision, hands and feet to explore their social and physical environment.

Supine Development in the Newborn Infant: 0-4 weeks

During the newborn period infants are adapting to the new social and physical environment.  The sensorimotor abilities they acquired while in the buoyant fluid intrauterine environment are harnessed and adapted to the new constraints on movement imposed by gravity and the surfaces they encounter. The limbs have weight and movement of the limbs produces reactive forces as well as momentum which need to be factored into the control of their movements.

Newborn infants when they are awake and alert and supine on a firm surface respond to visual and auditory events in the environment and actively produce spontaneous movements of the limbs.  

The looking, listening and moving provides opportunities for linking what they do to what is seen, heard and felt, creating the perception-action loops that are the basis for making the shift from spontaneous exploratory movements to intentional, goal directed actions that allow the infant to interact with people, things and events in their environment in the coming months

Limb Movement Synergies at Birth

The multi-segmented structure of the body provides the basis for producing the varied movement patterns seen in human actions.  To simplify control of the many degrees of freedom inherent in a multi-segmented body,  spontaneous infant movements are constrained and organised into synergies.

During the neonatal period the lower extremity synergy is characterised by intra-limb coupling of hip and knee flexion or extension. The upper limb synergy combines shoulder and elbow extension with extension of the fingers and wrist.

Over the next few months as the infant explores different ways of interacting with the environment and as the frontal motor areas of the brain become more active, the strong intralimb coupling lessens as movement are adapted to allow for effective interaction with the environment.

Behavioural States and Movement

When awake infants shift between several different states which affect the organisation of their spontaneous movements.

In an alert but quiet state movement is minimal. The alert but quiet state is often associated with visual attention to the infant's own hand or the face of a social partner and other interesting visual stimuli in the environment.

In the alert and active state infants engage in bouts of vigorous spontaneous movements of the limbs.

In the distressed state the infant's movements are ongoing and very vigorous. Jitters and trembling may be present in the limbs.  

Newborn Head Posture and Movements

Generally the newborn's head is rotated to one side, often with a preference for a particular side. Neck rotation is associated with neck extension. This tendency to rest with the head rotated to one side is in part influenced by the round shape of the back of the head and weakness in the neck muscles. Infants often have a preferred side, usually to the right. The reason for this tendency is unclear.

A prominent feature of head rotation in the first two months is the tendency for rotation to be coupled with neck extension and lateral flexion to the opposite side, which is a reflection of the balance in activity between the sternocleidomastoid (SCM) muscles and deep neck flexor muscle activity.

The infant is able to turn the head to the midline, and can sustain the position briefly, especially when supported by visual attention to an interesting person, object or event.

Typically the head is held in the mid-position for brief periods of time when the infant is actively moving the limbs or is distressed. This is possibly due to increased activity in the neck and trunk muscles associated with the kicking actions.

Over the next few weeks infants develop the bilateral antigravity neck muscle strength and control needed to counteract the force of gravity (which creates a turning moment acting on the COG of the head)  and maintain the head in midline for longer periods of time.

Newborn Rolling

In newborn infants with typical limb stiffness (muscle tone), head turning may initiate partial rolling to the side.  This response may be due to the neonatal neck righting reflex but may also be because turning of the neck shifts the infant’s weight  laterally which destabilizes the trunk and the infant "'topples"  over to side lying.

Visual Attention

From the first weeks infants pay attention to interesting objects that come into their field of vision.  Visual attention is usually associated with cessation of limb movements.  When the head is supported in the midline the newborn infant will look at the face of a caregiver for extended periods of time. Infants will turn the head away when they need a break from the intensity of this focussed social interaction.  

When the head is supported the newborn can move the head to bring the social partner's face into the centre of the visual field. When paying attention to a social partner, infants will mirror theirc facial expressions and even stick out the tongue if this has been demonstrated.

Newborn infants engage in sustained visual regard of their own hands. Interestingly, they also pay close attention to the hands of a caregiver.

General Movements

Extensive research has described the characteristics of the complex movements that involve the entire body observed in infants from 0-2 months. “These movement, referred to a writhing general movements, are characterised by a variable sequence of neck, arm, trunk, and leg movements. They wax and wane, varying in intensity, speed, and range of motion, and have a gradual onset and end. Rotations along the axis of the limbs and slight changes in the direction of movement make them appear fluent and elegant and create the impression of complexity and variability.”

Lower Limb Posture, Range of Motion and Kicking Actions

In infants born at term range of movement (ROM) of the hips and knees is limited by muscle tightness and increased muscle tone (stiffness) in the lower limb flexor muscles that result from the flexed posture in the restricted space in the uterus in the last weeks of intrauterine life.  The restriction in hip extension is referred to as neonatal hip flexion contracture.

During periods of relative quietening of movement, the hips are flexed, abducted and laterally rotated and the infant lies with the feet lifted up off the supporting surface.  The knees cannot be fully extended and when passively extended they recoil back to a more flexed position.

Newborn kicking actions are characterized by a decrease in the range of hip flexion, along with some extension of the knee. The ankle remains in dorsiflexion with the toes in flexion. This relative extension of the hip and knee is followed by a return to the more flexed resting position.

Upper Limb Posture and Movements

Bly (1994) states that when the newborn infant is lying quietly, the upper arms rest on the supporting surface close to the body, with the shoulders in slight external rotation, the elbows in flexion and with the hands slightly open.

Spontaneous movements of the upper limbs often bring the hand into the infant's visual field and a period of quiet may ensue as the infant pays attention to the hand.

“To test whether newborn babies have voluntary control over their limbs, spontaneous arm-waving movements were measured in the dark while the baby lay supine with its head turned to one side. A narrow beam of light was shone over the baby's nose or chest in such a way that the arm the baby was facing was only visible when the hand encountered the, otherwise, invisible beam of light. The results showed the babies were capable of precisely controlling the position, velocity, and deceleration of their arms so as to keep the hand visible in the light. The findings indicate that newborns can purposely control their arm movements to meet external demands and that the development of visual control of arm movement is underway soon after birth.” 

Spontaneous movement of the upper limbs also brings the infant's hands into contact with the face. This is a familiar experience for the infant as hand-to-mouth is a common intrauterine movement pattern.

Large range movements of the shoulder and elbows are seen, with opening of the fingers when the elbow is extended and flexion of the fingers seen with elbow flexion.

Spontaneous movements of the fingers are initially mainly grasping and hand opening, but including with increasing frequency a variety of hand postures, including pointing with the forefinger, thumb to forefinger, simultaneous flexion of the forefinger and middle finger, as well as ring and little finger.  

Not only do infants move their fingers individually, but a study by Nagy et al (2014) demonstrated that newborn infants are able to imitate a demonstration of one, two and three finger extension patterns.

Strong finger flexion occurs when the hand is stimulated especially on the ulnar side – known as the palmer grasp response. When traction is applied to the arm, the fingers flex synergistically with the elbow and shoulder.  

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