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.  

Supine Development in the 1-2 Month Period

During the 1-2 month period the infant is awake and alert for longer periods of time, increasingly responds to sounds and sights from the environment and gains more control of movements of the head and limbs

General and fidgety movements

General movements continue to be characterized by writhing movements that involve the head, trunk and extremities in the 1-2 month period. However, towards the end of this period fidgety movements (FMs) are increasingly present (Einspieler 2016)

Einspieler C, Peharz R, Marschik PB. Fidgety movements - tiny in appearance, but huge in impact. J Pediatr (Rio J). 2016 May-Jun;92(3 Suppl 1):S64-70.

Writhing general movements in a healthy full term infant are described as complex and involve the entire body, notably arm, leg, neck, and trunk movements in variable sequences. They wax and wane, varying in intensity, speed, and range of motion, and have a gradual onset and end.

Rotations around the limb axes and slight changes in the direction of movement create the impression of fluency and elegance.

FMs are small movements of moderate speed with variable acceleration of the neck, trunk, and limbs in all directions. They may appear as early as six weeks after term, but usually occur from around 9 weeks until 16–20 weeks, occasionally even a few weeks longer. They fade out when antigravity and intentional movements start to dominate.

The presence and character of fidgety movements are good indicators of the integrity of the infant's nervous system (Einspieler 2016).

Einspieler C, Peharz R, Marschik PB. Fidgety movements - tiny in appearance, but huge in impact. J Pediatr (Rio J). 2016 May-Jun;92(3 Suppl 1):S64-70.

Head control and neck movements

At the beginning of the 1-2 month period the infant still tends to lie supine with the head turned to one or the other side. Head rotation continues to be associated with some neck extension and lateral rotation.

Head turning may be associated with an asymmetrical tonic neck reflex (ATNR) posture, but this is not obligatory.

By the end of the 1-2 month period the infant is more inclined to hold the head in the midline and easily turns the head to look at interesting objects and events in the environment.

At  this age infants tend to lie with the upper limbs abducted and extended, a position that helps to stabilize the trunk and provide a stable base for head movements and kicking (Bly 1994).

The infant is also able to combine neck rotation with extension of the head to look upwards.

However, control of the exact position of the head is clearly still developing, as rotation is usually associated with some neck extension and lateral flexion. This combination of movements suggests that the movement is brought about by contraction of the sternocleidomastoid muscles, with limited action in the deep neck stabilizers (Bly 1994).

The 1-2 month old infant is able to visually follow an object from the side to the midline, as well as follow an object moved in a downwards direction.  

Upper limb actions in the 1-2 month period

During periods of relative quiet the one-month-old infant adopts a variety of postures of the upper limbs.  Abduction of the shoulders with the upper arms resting on the support surface is often observed – in this position the upper limbs serve as outriggers and help to stabilize the trunk when moving the head and lower extremities.  Interestingly this co-opting of the upper limbs for a postural function during this period is associated with a decrease in the occurrence of swiping actions  towards objects within reach (von Hofsten 1993).

von Hofsten C, Rönnqvist L. (1993) The structuring of neonatal arm movements. Child Dev. 64(4):1046-57

Head rotation may be associated with the fencing position (extension of the face elbow with flexion of the skull elbow). However this association decreases over the 1-2 month period, and importantly, is never obligatory.  

The tendency to abduct the shoulders and use the upper limbs as outriggers decreases towards the end of this period when infants start to bring their hands into the midline.  

At the beginning of the 1-2 month period infants produce large range swiping movements of the upper extremities.  These swiping movements are associated with elbow extension and extension of the fingers. The hand comes close to the object, but mostly does not make contact.

Over the coming weeks the infant gain more control over reaching movements and starts to reach towards objects within easy reach with greater success.  The extension of the fingers seen in the one month old infant become less pronounced (von Hofsten 1984).

von Hofsten, C.  (1984). Developmental Changes in the Organization of Pre-reaching Movements. Developmental Psychology 20(3), 378–388.

The infant brings the hand into the proximity of the toy and then uses small range movements of the shoulder and elbow to explore different ways of touching and grasping the toy.

Towards the end of this period (10-12 weeks), as the infant's ability to steady the head and trunk when moving the upper limbs becomes more reliable they gain more control of reaching towards toys.  They are able to bring the hand into contact with the toy and start to use the fingers to explore it.  

This is the start of the ability to stabilise the position of the hand in space and at the same time use independent finger movements to gather information about the texture, structure and behaviour of objects. Visual attention to the toy and the hand provides further information that starts to link what is felt and what is seen.

Exploratory hand movements in the 1-2 month period

During this period infants continue to use their hands to gather information about the surfaces they encounter.  Contact with a surface is often associated with exploratory movements of the hand across the surface, or repeated flexion and extension of the fingers.

Independent movements of the fingers are also frequently seen, especially when the infant  is socially engaged or is paying attention to an object within reaching distance.

Postural sway and postural stability

Observing an infant during periods of quiet supine lying allows one to observe the postural sway present in the trunk. These exploratory movements allow the postural system to gather the sensory information needed for estimating the position of the body as a whole and explore the most effective strategies to maintain a stable posture (Dusing 2010).

Dusing, S. C., & Harbourne, R. T. (2010). Variability in Postural Control During Infancy: Implications for Development, Assessment, and Intervention. Physical Therapy, 90(12), 1838–1849.

Lower extremity movements

The 1-2 month old infant engages in periods of relative calm when the feet rest on the support surface with varying amounts of flexion of the hips and knees.  

The range of ankle plantar flexion has also increased.

The 1-2  month old still engages in extended periods of kicking. Movement patterns include repeated single leg kicking with alternate leg kicking and bilateral hip and knee flexion and extension.

At this age hip and knee movements are still coupled. The ankles remain in dorsiflexion with intermittent flexion and extension of the toes.

Lower limb bridging during the 1-2 month period

From time to time one or both feet push down on the support surface. Pushing down with one foot is associated with head and trunk extension and lateral weight shift.

Pull-to-sit  

The infant's response to the pull-to-sit (PTS) manoeuvre is often used as a test when assessing motor development. It provides a good measure of the infant's neck muscle strength as well as the development of effective anticipatory postural responses.

By the end of the 1-2 month period, infants have learned to anticipate being lifted and will participate in the PTS manoeuvre by engaging the neck and trunk flexor muscles, stiffening the upper limbs and flexing the hips.

The head is held in line with the trunk as the shoulders are lifted.

Once in the upright position the head is held erect, and the infant is able to lift the face to look at the person who has pulled him into sitting.

Supine during the 3-4 month period (12-21 weeks)

During the 3-4 month period infants spend more time in an alert awake state than before, allowing for more time to observe, explore and interact with the social and physical environment  

Socially they are becoming aware of their ability to engage parents and other family members, are learning how to attract their attention and keep the social interaction going using smiles, facial mirroring (imitation) and vocalization.

Their innate curiosity coupled with the ability to see clearly over longer distance draws them to paying attention to people and events in the environment. (Brazelton2006).

Brazelton TB (2006) Touchpoints Birth to Three

The 3-4 month old infant’s ability to self-regulate their levels of arousal is improving as they learn to self-soothe and turn away from visual events that they find unpleasant.  When used, they start to  retrieve a pacifier and return it to the mouth.  

General and fidgety movements in the 3-4 month peiod

At this age fidgety movements (FMs) can still be observed. FMs are small movements of moderate speed with variable acceleration of the neck, trunk, and limbs in all directions They may appear as early as six weeks after term, but usually occur from around 9 weeks until 16–20 weeks, occasionally even a few weeks longer. They fade out when antigravity and intentional movements start to dominate. (Einspieler  2016)  

Einspieler C, Peharz R, Marschik PB. Fidgety movements - tiny in appearance, but huge in impact. J Pediatr (Rio J). 2016 May-Jun;92(3 Suppl 1):S64-70.

Head control and neck movements

During the 3-4 month period the infant's ability to maintain the head in the midline becomes fully established. This allows them to visually focus on people and toys presented in the midline.

The infant has learned to flex the head on the neck as the deep neck stabilizer muscles become more active and are able to balance the activity of the sternocleidomastoid muscles (which tends to extend the neck with bilateral activation).

Flexion of the head on the neck also allows the infant to look down to bring objects that are held in the hands into the centre of the field of vision for detailed inspection (foveal vision).

The infant now easily turns the head through full range of motion, keeping the head in flexion, without associated side flexion seen at an earlier age. Rotation of the neck does not affect the position of the extremities.

The infant is also able to rotate and extend the neck to look at an object to the side and above the head.

Being lifted

During the 3-4 month period infants increasingly anticipate being lifted when they see the caregiver preparing to pick them up. This caregivers's intention is signalled by their hands moving towards the infant's chest who in turn starts to recruit the neck and trunk muscles in anticipation of being lifted (Reddy 2013)..

Reddy, V., Markova, G., & Wallot, S. (2013). Anticipatory Adjustments to Being Picked Up in Infancy. PLoS ONE, 8(6), e65289

As the infant's neck strength increases,  caregivers provide less support for the neck when they lift the infant. The infant tends to have better control of neck lateral flexion and extension than flexion against gravity. Turning infants as they are lifted allows them to maintain control of the position of the head.      

Pull-to-sit

Increasingly infants anticipate being lifted from supine into sitting when the caregiver grasps and pulls on their hands.  (This pull-to-sit manoeuvre is often used to assess head control.) The infant flexes the neck and trunk, recruits the upper limb muscles in response to the traction on hands, and lifts the lower limbs up off the support surface.

When tipped backwards from sitting the infant is able to flex the neck  to control the position of the head as the torso is lowered.

Looking, visual convergence and tracking

The infant is now able to track an object moved from one side to the other across the midline.  Tracking a moving upwards is also present, with downward tracking being less consistent.

Kicking and reaching in supine contribute to head and trunk stability

When placed in supine on a firm flat surface healthy typically developing infants are very active, with repeated bouts of kicking, reaching for toys within easy reach and actively using the hands and feet to explore the surrounding surfaces and their own bodies. They are very curious and eager to know what is going on around them turns their heads to look at interesting and novel events in the environment.

This activity is important for strengthening trunk and limb muscles. Infants with high activity levels of the upper limbss as measured by full-day wearable sensors have been shown to have higher  cognitive, language and motor scores (Shida-Tokeshi, 2018).

Shida-Tokeshi, J., Lane, C. J., Trujillo-Priego, I. A., Deng, W., Vanderbilt, D. L., Loeb, G. E., & Smith, B. A. (2018). Relationships between full-day arm movement characteristics and developmental status in infants with typical development as they learn to reach: An observational study. Gates open research, 2, 17.

This period also sees an increasing ability to stabilise the trunk when moving the extremities allows the infant more control over their increasing tendency to engage in intentional and goal directed reaching and exploratory movements of the hands and feet.  

Upper extremity and hand actions

During moments of relative quiet 3-4 month old infants assume a variety of upper limb postures, sometimes with the shoulders in abduction and the extremity held away from the torso but frequently with the hands together in the midline.  

The tendency to bring the hands together in the midline is particularly prominent at the beginning of the 3-4 month period.  Infants will visually inspect them for long periods of time.  This visual attention is aided by the infant's ability to flex the head on the neck and at the same time look downwards to bring the hands into the centre of the field of vision for a clearer view.

Reaching towards a toy presented in the midline is bilateral, with one hand usually making contact before the other.

Lower limb actions

The 3-4 month old infant has acquired the ability to move the lower limbs in a variety of ways that reflect the ability to flex and extend the hips and knees in different combinations. This ability to disassociate hip and knee movements differs from the tendency for the strong intra-limb association in 1-2 month old infant.

LE posture during periods of relative quiet

During periods of relative quiet the 3-4 month old infant may lie with the hips and knees flexed, with the feet lifted up off the support surface (SS). This is associated with posterior pelvic tilt.  At this time hip flexion and extension are associated with some hip abduction.

Over the next weeks the range of hip extension increases and hip abduction in extension decreases. Crossing of the feet is frequently seen. The 3-4 month infant will often put one of both feet flat on the support surface with the knees flexed.  Pushing down on the support surface with both feet does not yet result in lifting the buttocks up (bridging). Pushing down with one foot leads to extension of the ipsilateral hip with forwards rotation of the pelvis.  This action may initiate rolling to the side.

Periods of repeated unilateral and reciprocal kicking are still seen. The trunk is held steady and is symmetrical during periods of active kicking.

Foot movements

The 3-4 month infant also brings the feet together and engages in exploratory ankle movement. Isolated ankle dorsi- and plantar flexion movements are frequently seen.  

Rolling

Rolling from supine to lying on the side is becoming more frequent.  The infant uses a variety of patterns to initiate rolling. In the sequence of frames below you see Will initiating rolling  by reaching across the body to reach a toy. As he brings his arm forwards he extends his neck and trunk. At the same time he pushes away with his right foot which helps to shift his weight to the left.

Supine in the 5-6 month period (20-28 weeks

During the 5-6 month period infants' behaviour and actions are becoming more intentional and goal oriented. They become increasingly aware of their ability to initiate social encounters and know how to attract and maintain the attention of social partners ( Brazelton 2006)

Brazelton TB (2006) Touchpoints Birth to Three

The use of their hands and feet to explore surfaces and objects becomes more focused and intentional.

The 5-6 month period is characterized by an increasing ability adapt their postural alignment and stability, and their movements to achieve a desired goal.  

During this period the infant also becomes more mobile as they learn to roll from supine to prone and start to use this mobility to move around in the cot and on the floor.

Emerging abilities during this period

• Improved ability to steady the trunk when the limbs are moved.
• Increasing strength in the hip and trunk flexor muscles which allows the infant to lift both feet up off the support surface in a sustained manner.
• Posterior pelvic tilt is associated with bilateral hip flexion which allows the infant to reach for the feet and bring one foot to the mouth.
• Increasing ability to perform isolated movements of the lower limb joints, with uncoupling of hip and knee flexion.
• Increasing control of reaching for objects and the ability to hold an object with one hand and explore its properties with the other hand.
• Emerging tendency to bang and shake toys and pass them from one hand to the other.
• Prominence of exploratory movements of the hands and feet - also reflecting the ability to adapt movement of the limbs to suit the task and the ability to more isolated movements of the distal segments.
• Ability to actively initiate and control rolling from supine to side lying and prone.

Head and trunk stability

The 5-6 month infant has full range of neck rotation and can visually follow a moving object in all directions, including from one side to the other, and across the midline.

Head-on-neck flexion is well established and allows the infant to watch the hands when reaching for, or manually inspecting, a toy in held in the midline above the chest.

The 5-6 month infant is able to keep the head and trunk steady when moving the limbs. This allows for more control of intentional upper limb reaching movements towards an object, as well as holding and manipulating objects.

Lower limb actions in supine

Active 5-6 month infants continue to move the lower limbs vigorously, using a variety of patterns, including reciprocal kicking movements, bilateral hip and knee flexion, and bilateral hip and knee extension.

Some of the time the infant lies with the feet resting on the support surface, particularly when engaged with a toy or when watching what is happening in the environment.

At other times, when the general level of arousal is higher, the legs cycle through a variety of postures with the feet lifted up off the support surface. These kicking actions are associated with trunk muscle activity to stabilise the trunk.

With both feet on the support surface the infant is starting to lift the buttocks up off the surface (bridge).

Another pattern frequently seen is bilateral flexion of the hips, in most instances associated with knee flexion, but sometimes with knee extension. The range of hip flexion increases with increasing trunk muscle strength and control of posterior pelvic tilt.

Infants start to reach for, and grab their feet.

Rolling

During the 5-6 month period infants become progressively more adept at rolling from supine to prone. They explore different options for initiating rolling. Lifting the lower limbs and toppling over is one option.

The difficult part of rolling is lifting the head and trunk to free the arm that is trapped under the torso as the body moves through side lying into prone.

This is achieved by initiating side flexion of the head and trunk against gravity, lifting the torso and freeing the upper limb to move forwards as the infant moves from through side lying into prone.

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