Infant Development

Original Editor - Robin Tacchetti based on the course by Eskay
Top Contributors - Robin Tacchetti and Jess Bell

Introduction

One of the most critical periods for developmental growth occurs during early childhood. Development refers to changes in abilities and skills that improve daily functioning. Meaningful changes in development facilitate a highly dependent child to become an independent individual. Development follows general principles that are universal to all human beings:

• Change: A progressive series of changes occur during development. These changes are both qualitative and quantitative.

• Continuous Process: Throughout the life of an individual there is continuous development. Each stage of development builds the groundwork for the next stage.
• General to Specific: Movement patterns begin with general actions progressing to specific. Large muscle movements precede refined muscle movements.
• Sequential: Development always follows certain sequences and occurs in an orderly manner.
• Predictable: Common features and traits occur in every stage that have predictable, orderly patterns.
• Heredity and Environment: Development is a product of family, culture and social influences. All of these attributes contribute simultaneously to the individual's development.

• Maturation: Development relies on learning and maturation. Maturation refers to the biological growth or changes that naturally occur over time. These changes take place in the brain and nervous system, and facilitate development in thinking and motor skills. The brain has to develop or mature enough to allow for the next skills in the sequence to develop.
• Individual Rates of Growth: Development follows usual sequences and patterns, but each individual will develop at their own rate.
• Specific Directions:

1. Cephalocaudal: Infants develop by first controlling their head before being able to control their arms and legs. Development takes place in a downward direction with the arms preceding the legs.
2. Proximodistal: Infants learn to control the centre of their body before the periphery; the head and trunk before the arms and legs.

Flexed Posture

In infants born at term, range of motion (ROM) of the hips and knees is limited by muscle tightness and increased muscle tone (stiffness) in the lower limb flexor muscles. This flexed posture occurs because there is restricted space in the uterus in the last weeks of intrauterine life. This position 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 their 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:
  • Characterised 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

Muscle Synergy

Muscle synergies refer to consistent muscle coordination patterns that accurately generate a specific motor action. In neuroscience it has been proposed that muscle synergies are a mechanism for neural control of movement.

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.

• Lower limb synergy pattern includes intralimb coupling of:
  • Hip flexion, knee flexion and dorsiflexion
  • Hip extension and knee extension

• Upper limb synergy pattern includes a combination of:
  • Shoulder and elbow extension with extension of the fingers and wrist
  • Flexion of the elbow with finger flexion

General and Fidgety movements

Whole body movements, called general movements or GMs,  are complex and involve the entire body, notably the arm, leg, neck, and trunk in variable sequences.

GMs continue to be characterised by writhing movements that involve the head, trunk and extremities in the 1-2 month period. They wax and wane, varying in intensity and speed and range of motion. Rotations around the limb axes and slight changes in the direction of movement create the impression of fluency and elegance. GMs have a gradual onset and a gradual end. However, towards the end of this period, fidgety movements (FMs) are increasingly present.

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 FMs are good indicators of the integrity of the infant's nervous system.

Resources

• Newborn Perceptual Motor Behaviour

• Understanding Newborn Behaviour
• Development Skills Training for the 1-2 month old
• Motor Development Principles