Infant Development in Supine

Original Editor - Pam Versfeld

Top Contributors - Stacy Schiurring and Jess Bell  

Introduction

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 their head and trunk, which in turn allows them to use their vision, hands and feet to explore their social and physical environment. Treatment interventions and management should focus on encouraging infants with developmental delays to thrive during their early years of life, as this period is critical for maximising their potenitial.

Important definitions:

• Alert and active state: infants engage in bouts of vigorous spontaneous movements of the limbs
• Alert and 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
• Writhing movements: From birth at term until 6-9 weeks of age, general movements are known as writhing movements.
• Fidgety movements: “small movements of moderate speed with variable acceleration of the neck, trunk, and limbs in all directions”. They typically replace writhing movements and are "general, circular movements of small amplitude and variable acceleration throughout the body. They are present continuously in an awake infant”

This article describes infant motor development when lying supine on a firm flat surface. In this 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.

Supine Development in the Newborn Infant: 0-4 weeks

During the newborn period, infants are adapting to their 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.

• Their limbs have weight, and movement of the limbs produces reactive forces and momentum - these need to be factored into the control of their movements
• When awake and alert on a firm surface, they can respond to visual and auditory events in the environment and actively produce spontaneous movements of the limbs
• Observation of and interaction with their surroundings create perception-action loops that are the basis for making the shift from spontaneous exploratory movements to intentional, goal directed actions

Limb Movement Synergies at Birth

• Lower extremity synergy is characterised by intra-limb coupling of hip and knee flexion or extension
• 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 the frontal motor areas of the brain become more active, the strong intra-limb coupling lessens. Movement is adapted to allow for effective interaction with the environment.

Behavioural States and General Movements

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

• Alert but quiet state: movement is minimal and is often associated with visual attention to own hand, the face of a social partner or other interesting environmental visual stimuli
• Alert and active state: bouts of vigorous spontaneous limb movements
• Distressed state: movements are ongoing and very vigorous, limb jitters and trembling may be present

Research describes the characteristics of the complex movements that involve the entire body observed in infants from 0-2 months.

“These movements, 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.” - Einspieler et al., 2008

Newborn Head Posture and Movements

• Generally, newborns keep their head rotated to one in supine, and tend to have a preferred side (typically to the right)
• Neck rotation continues to be associated with neck extension and lateral flexion to the contralateral side
• Can turn the head to midline and briefly sustain the position
  • with visual attention to an interesting person, object or event
  • when actively moving limbs or distressed
  • over the next few weeks, they develop the bilateral antigravity neck muscle strength and the control needed to counteract the force of gravity and maintain their head in midline for longer periods

Visual Attention

• From the first few weeks, infants pay attention to interesting objects that come into their field of vision
  • when their head is supported in midline, they will look at the face of a caregiver for extended periods of time; they will turn their head away when they need a break
  • when the head is supported, they can move their head to bring their social partner's face into the centre of their visual field, and can mirror facial expressions
• Visual attention is usually associated with cessation of limb movements
• Infants engage in sustained visual regard of their own hands and tend to pay close attention to the hands of a caregiver

Newborn Rolling

Typical limb stiffness (muscle tone) in newborns allows head turning to initiate partial rolling into side-lying. This response may be due to the neonatal neck righting reflex, but may also be because turning the neck shifts the infant’s weight laterally, which destabilises the trunk, "toppling" them over into side-lying.

Upper Extremity Posture and Movements

• During periods of relative quietening of movement:
  • upper arms rest on the supporting surface close to the body, with the shoulders in slight external rotation, the elbows in flexion and the hands slightly open
• Spontaneous movements of the upper limbs:
  • bring the infant's hand into their visual field and a period of quiet may ensue as the infant pays attention to their hand
  • bring the infant's hands into contact with their face and / or hand-to-mouth

• Hand and finger movements:
  • large range of motion (ROM) of the shoulder and elbows are seen, with the fingers opening when the elbow is extended and the fingers flexing with elbow flexion
  • spontaneous movements of the fingers include (1) grasping and hand opening, (2) pointing with the forefinger, (3) thumb to forefinger, and (4) simultaneous flexion of the forefinger and middle finger, and the ring and little finger
  • infants are able to imitate a demonstration of one, two and three finger extension patterns
  • palmer grasp reflex (response): when gentle pressure is applied to an infant's palm, the infant's fingers flex to hold the examiner's finger. The pressure applied to the palm produces traction on the tendons of the fingers, which encourages the infant to cling to the examiner's finger. The infant's thumb is not affected by this reflex.

Lower Extremity Posture, Range of Motion and Kicking Actions

Cramped intrauterine environment causing neonatal hip flexion contracture

In infants born at full-term, hip and knee ROM is limited by lower extremity flexor muscle tightness and increased muscle tone, which results from the flexed posture assumed in the last weeks of intrauterine life. This hip extension restriction is referred to as neonatal hip flexion contracture.

• During periods of relative quietening of movement:
  • hips are flexed, abducted and laterally (externally) rotated, and feet are lifted off the supporting surface 
  • knees cannot be fully extended; when passively extended, they recoil back to a more flexed position

• Newborn kicking actions are characterised by:
  • decrease in hip flexion ROM and some knee extension
  • ankle reamins in dorsiflexion with toes in flexion
  • after kicking, the infant returns to the more flexed resting position

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 environmental sounds and sights, and gains more control of head and limb movements.

General and Fidgety Movements

General movements continue to be characterised by writhing movements that involve the head, trunk and extremities, but fidgety movements become increasingly present towards the end of this period.

• Writhing movements are complex and involve the entire body in variable sequences
• Rotations around the limb axes and slight changes in the direction of movement create the impression of fluency and elegance
• Fidgety movements 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
  • they fade when antigravity and intentional movements begin to dominate
  • the presence and character of fidgety movements are good indicators of the integrity of the infant's nervous system

Head Control and Neck Movements

Asymmetrical tonic neck reflex: extension of arm and leg on the same side toward which infant has turned head, and flexion of arm and leg of the opposite side

At the beginning of this period infants still tend to lie in supine:

• they lie with their head turned to one or the other side
• head rotation continues to be associated with some neck extension and lateral rotation
• head turning may also be associated with an asymmetrical tonic neck reflex (ATNR) posture

By the end of the 1-2 month period:

• they are more inclined to hold their head in the midline
• they easily turn their head to scan and observe the environment and able to combine neck rotation with extension of the head to look upwards

Infants tend to lie with their upper limbs abducted and extended, a position that helps to stabilise the trunk and provide a stable base for head movements and kicking.

Infants are able to visually follow an object from the side to the midline, as well as follow an object moved in a downwards direction.  

Upper Extremity Posture and Movements

During periods of relative quiet, the one-month old infant adopts a variety of postures of the upper limbs:

• abduction of shoulders with upper arms resting on the support surface allows the the upper extremities to stabilise the trunk against movements of the head and lower extremities
• this strategy decreases towards the end of this period as infants begin to bring their hands into the midline

Head rotation may be associated with the fencing position (extension of the face elbow with flexion of the skull elbow).

At the beginning of this period in supine:

• infants produce large range swiping movements of the upper extremities, which are associated with elbow extension and finger extension
  • during these movements, the hand comes close to the object but rarely makes contact

• over the coming weeks, the infant gains more control over reaching movements and starts to reach towards objects within easy reach with greater success
  • the infant brings the hand into the proximity of the toy and uses small range movements of the shoulder and elbow to explore different ways of touching and grasping the toy

By the end of this period:

• the infant is better able to steady the head and trunk while reaching with upper extremities
• the infant can bring their hand into contact with a toy and explore with their fingers
  • this marks the beginning of the ability to stabilise hand position in space while using independent finger movements to gather information about objects
  • visual attention also improves and provides additional information about objects

Postural Sway and Stability

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.

Lower Extremity Posture and Movements

• Supine posture during relative periods of calm: feet rest on the support surface with varying amounts of hip and knee flexion
• Infants at this stage still engage in extended period sof kicking: movement patterns include repeated single leg kicking with alternate leg kicking and bilateral hip and knee flexion and extension
• Hip and knee movements are still coupled:
  • ankles remain in dorsiflexion with intermittent flexion and extension of the toes
  • plantar flexion ROM has increased

Lower Extremity Bridging

• From time to time, the infant pushes one or both feet 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 manoeuvre is often used as a test when assessing motor development. It provides a good measure of the infant's neck muscle strength and 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 pull-to-sit manoeuvre by engaging their 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 examiner.

Supine Development in the 3-4 Month Period

• Infants at this stage spend more time in an alert awake state, which allows for more time to observe, explore and interact with the social and physical environment  
• They become aware of their ability to engage caregivers, are learning how to attract their attention, and engage in social interaction using smiles, facial mirroring (imitation) and vocalisation
• They are better able to self-regulate their levels of arousal as they learn to self-soothe and turn away from visual events that they find unpleasant
• Fidgety movements can still be observed

Head Control and Neck Movements

• An infant's ability to maintain their head in the midline becomes fully established, which allows them to visually focus on people and toys presented in the midline

• Infants now easily turns the head through full range of motion, keeping their head in flexion, without associated side flexion seen at an earlier age. Rotation of the neck does not affect the position of the extremities
• They are also able to rotate and extend their neck to look at an object to the side and above the head
• 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).

Visual Convergence and Tracking

• Infants are now able to track an object moved from one side to the other across midline
• Tracking upwards is also present, but tracking downward is less consistent.

Being Lifted

Infants increasingly anticipate being lifted when they see their caregiver preparing to pick them up. The 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.

• As the infant's neck strength increases, caregivers provide less neck support lifting the infant
• Infants tend to have improved 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 their head

Pull-to-Sit

• Infants increasingly anticipate being lifted from supine into sitting when the caregiver grasps and pulls on their hands:
  • infants flex their neck and trunk, recruit their upper extremity muscles in response to the traction on their hands, and lift the lower extremities off the support surface
• When tipped backwards from sitting, infants are able to flex their neck to control the position of the head as the torso is lowered to the support surface

Postural Stability

When supine on a firm flat surface, infants are very active, with repeated bouts of kicking, reaching for toys within easy reach and actively using their hands and feet to explore the surrounding surfaces and their own bodies. They are very curious and turn their heads to look at interesting and novel events in the environment.

• This activity is important for strengthening the trunk and limb muscles. Moreover, infants with high activity levels of the upper extremities as measured by full-day wearable sensors have been shown to have higher cognitive, language and motor scores
• This period also sees an increasing ability to stabilise the trunk when moving the extremities, which allows the infant more control to engage in intentional and goal directed reaching and exploratory movements of the hands and feet

Upper Extremity Posture and Movements

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

Hands together in midline:

• infants will visually inspect hands for long periods of time
• this visual attention is aided by the infant's ability to flex their head on their neck and at the same time look downwards to bring their 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 Extremity Posture and Movements

3-4-month-old infants have acquired the ability to move their lower extremities in a variety of ways due to their ability to flex and extend hips and knees in different combinations.

In supine during periods of relative quiet:

• infants may lie with their hips and knees flexed, with their feet lifted off the support surface - this is associated with posterior pelvic tilt
• hip flexion and extension are associated with some hip abduction

By the end of this period:

• hip extension ROM increases
• hip abduction ROM in extension decreases
• crossing legs at the feet is frequently seen

Bridging

The infant will often put one or 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

Kicking

• Periods of repeated unilateral and reciprocal kicking continue at this stage
• the trunk is held steady and is symmetrical during periods of active kicking

Foot Movements

• Infants bring feet together and engage in exploratory ankle movement
• Isolated ankle dorsiflexion and plantar flexion movements are frequently seen

Rolling

• Rolling from supine to lying on the side becomes more frequent
• Infants use a variety of patterns to initiate rolling

Supine Development in the 5-6 Month Period

• At this stage, an infant's behaviour and actions become more intentional and goal oriented (e.g. using hands and feet to explore objects and surfaces)
• Infants become increasingly aware of their ability to initiate social encounters and know how to attract and maintain the attention of social partners
• Infants are increasing able to adapt postural alignment, stability and movements to achieve a desired goal
• Infants become more mobile as they learn to roll from supine to prone, and start to use this mobility to move around on a supportive surface

Emerging Abilities During this Period

• Improved ability to steady the trunk when the limbs are moving
• Increasing hip and trunk flexor muscle strength, 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 allow the infant to reach for their feet and bring one foot to their mouth
• Uncoupling of hip and knee flexion allows for increased ability to perform isolated movements of the lower extremity joints
• Increased control while reaching for objects
• Increasing ability to hold an object with one hand and explore its properties with the other
• 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
• Ability to actively initiate and control rolling from supine to side-lying and prone

Head and Trunk Stability

• At this stage, infants have full neck rotation ROM
• They 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 their hands while reaching for or manually inspecting a toy held in midline above the chest
• They are able to keep their head and trunk steady when moving the extremities, which allows for more control of intentional upper extremity movements and holding

Lower Extremity Posture and Movements

In supine during periods of relative quiet:

• infants lie with their feet resting on the support surface, particularly when engaged with a toy or observing the environment
• they often lie with both hips flexed, commonly with knee flexion. Hip flexion ROM increases with improving trunk muscle strength and control of posterior pelvic tilt
• they start to reach for and grab their feet

Kicking

• Infants continue to move their lower limbs vigorously, using a variety of patterns, including (1) reciprocal kicking movements, (2) bilateral hip and knee flexion, and (3) bilateral hip and knee extension

Bridging

• With both feet on the support surface, infants begin to lift their buttocks off the support surface (into a bridge)

Rolling

• Infants become progressively more adept at rolling from supine to prone.
• They explore different options for initiating rolling

Atypical Development and Developmental Delay

Typical infant development occurs via an interaction between the development of the nervous system and various organ systems, and stimulation from the infant's social and physical environment. Infants that demonstrate atypical or developmental delay tend to be (1) less physically active, and (2) lack movement repetition. Therefore, they miss opportunities for motor learning and sensory integration.

To learn more about paediatric diagnoses which can cause developmental delays, please review the following Physiopedia Pages:

• Cerebral Palsy
• Down Syndrome
• Muscular Dystrophy
• Preterm Birth

The management and treatment of developmental delay should be an interdisciplinary team effort, and include primary care providers, neurologists, developmental and behavioral paediatricians, speech and language therapy (pathology), occupational therapy, physiotherapy, and nutritionists.Treatment strategies are usually multi-modal and often require input from multiple medical and rehabilitation disciplines, with strong family support.

Resources

Optional Additional Reading:

• Dusing SC, Thacker LR, Stergiou N, Galloway JC. Early complexity supports development of motor behaviors in the first months of life. Developmental psychobiology. 2013 May;55(4):404-14.
• Einspieler C, Peharz R, Marschik PB. Fidgety movements–tiny in appearance, but huge in impact. Jornal de Pediatria. 2016 May;92:64-70.
• von Hofsten C, Rosander K. The development of sensorimotor intelligence in infants. Advances in child development and behavior. 2018 Jan 1;55:73-106.