Unit 2 Study Guidance – Development & Postural Control Through the Lifespan
1. Typical Developmental Progressions
Cephalocaudal Pattern
Motor control develops from head to toe.
Example: Infants gain head control before trunk and lower extremity control.
Demonstrated when a baby first stabilizes the head, then learns to sit, crawl, and finally stand/walk.
Proximal to Distal Control
Motor strength and control progress from proximal (center) segments to distal (extremities).
Example: Control of shoulders and hips develops before hands and feet.
Creeping (hip control) precedes walking (knee/ankle coordination).
Gross Motor Before Fine Motor
Large body movements develop prior to refined, precise motions.
Example: Babies first wave or reach before they can grasp or manipulate small objects.
Reflexive to Volitional Movement
Early movements are automatic reflexes driven by sensory input (e.g., rooting reflex).
With brain maturation, voluntary control replaces reflexive activity.
Example: Spontaneous limb flailing evolves into intentional reaching and grasping.
Limited → Complex Degrees of Freedom (DOF)
Infants begin with stiff, limited movement and progress to fluid, multi-joint coordination.
Example: A newborn’s stiff limb motions transition into coordinated crawling and walking patterns.
Planes of Movement Progression
Sagittal plane – Flexion and extension (e.g., lifting head, rolling).
Frontal plane – Lateral flexion and side bending (e.g., reaching sideways in sitting).
Transverse plane – Rotational components (e.g., trunk rotation in crawling and walking).
Movement control expands from simple linear motions to complex, multi-planar tasks.
2. Key Developmental Milestones
Year One
Birth–3 months: Physiological flexion, developing head control, early prone extension.
4–6 months: Rolling (belly-to-back, back-to-belly), midline hand play, sitting with support.
6–9 months: Independent sitting, reaching for toys, pushing onto hands and knees.
9–12 months: Creeping, pulling to stand (half-kneel), cruising along furniture, independent walking by 12–18 months.
Key Concepts: Rapid motor learning, muscle strengthening, integration of primitive reflexes, emerging postural reactions.
Year Two
Walking refinement: Sideways, backward, carrying and pushing objects while walking.
Climbing stairs, toe walking, and maneuvering obstacles.
Running begins as fast walking and becomes more coordinated with alternating arm swing and push-off from toes.
Jumping emerges — first in place, then forward, backward, and down from low surfaces.
Key Concepts: Increasing strength, coordination, and environmental exploration.
Years 3–5
Refinement of gross motor skills: Running, jumping, climbing, kicking, catching, and throwing become smoother and stronger.
New movement patterns: Galloping and skipping emerge.
Improved balance, power, and speed as motor control and postural reactions mature.
Key Concepts: Integration of complex movement sequences and coordination across multiple planes.
3. Primitive (Infantile) Reflexes
Definition and Purpose
Automatic, involuntary movements triggered by sensory stimuli that promote survival and early development.
Example: Rooting Reflex — stroking the cheek causes the infant to turn toward the stimulus to aid in feeding.
Importance of Integration
As higher brain centers mature, primitive reflexes must integrate to allow voluntary, purposeful movement.
Persistence of primitive reflexes beyond the expected age can indicate neurological impairment and interfere with postural control and motor milestones.
4. Postural Reactions
Purpose
Automatic responses that maintain upright posture and balance against gravity.
Begin around 2–3 months and continue throughout life.
Work in concert with maturing sensory systems (vision, vestibular, proprioception).
Righting Reactions
Purpose: Keep the head and body oriented to midline and upright relative to gravity.
Optical Righting: Visual input used to realign head to vertical when tilted.
Labyrinthine Righting: Vestibular input realigns head when vision is occluded.
Body-on-Head Righting: Proprioceptive input from the body reorients head in space (e.g., when prone).
Example: Leaning sideways causes the head to automatically tilt opposite the direction to maintain upright gaze.
Equilibrium Reactions
Purpose: Maintain balance when the center of mass (COM) shifts due to displacement.
Body moves opposite the direction of the force (e.g., trunk bending and limb abduction).
Occur in multiple positions: prone, supine, sitting, quadruped, and standing.
Example: On a rocker board, the trunk and limbs adjust to restore stability.
Protective Reactions
Purpose: Prevent injury by extending limbs when balance is lost.
Includes the parachute response (arms extend forward to protect the head when falling).
Example: Extending an arm or leg when pushed to prevent a fall.
5. Postural Control Mechanisms
Definition of Postural Control
The ability to maintain stability (balance) and orientation (alignment) of the body relative to gravity, the environment, and the task.
Involves integration of sensory, motor, and cognitive systems.
Steady-State (Static) Balance
Maintaining COM within BOS during stillness.
Supported by antigravity muscles: erector spinae, abdominals, TFL, gastrocnemius, tibialis anterior.
Typical Postural Sway: Small, automatic, unconscious shifts in balance that occur even when standing still.
Anticipatory Balance Control (Feedforward)
Preparatory muscle activation prior to expected movement or challenge to stability.
Known as the “central set.”
Example: Tightening core muscles before lifting a box or stepping onto ice.
Involves planning and prediction to minimize loss of balance.
Reactive Balance Control (Feedback)
Response to unexpected external disturbances that displace the COM.
Triggered after the perturbation occurs.
Ankle Strategy
Used for small, slow perturbations on firm surfaces.
Muscles activated: Tibialis anterior (backward sway) and gastrocnemius (forward sway).
Hip Strategy
Used for larger or faster perturbations, or on unstable surfaces.
Muscles activated: Hip flexors and extensors.
Stepping (Reaching/Grasping) Strategy
Used when COM moves too far outside BOS.
A step or reach is taken to restore stability and prevent falling.
Adaptive Balance Control
Modifying balance strategies to meet demands of changing tasks or environments.
Example: Adjusting balance responses when walking on sand, ice, or uneven terrain.
Reflects the flexibility and learning capacity of the postural control system.
6. Integration and Clinical Application
All systems work together — sensory (vision, vestibular, somatosensory), motor, and cognitive — to maintain stability and orientation.
Experience and environmental variability enhance postural control and motor learning.
PTs use this knowledge to:
Identify abnormal development or balance dysfunctions.
Design interventions that target postural reactions and balance strategies.
Educate families on positioning, play, and safety during development.
Implement fall prevention and balance training in older adults.