posture
postural control
infant stance
- position adopted by parts of the body
- ability to detect changes in center of gravity in relation to base of support: necessary for stability (which is greatest when center of gravity passes through center of base of support)
- bigger base of support to stand because head is big-slight forward lean to balance weight-head=biggest rate limiter for stability
development of postural control
- minimal control-can hold head for a few seconds in prone (1 mo)
- moderate control-can hold head and chin steadily up (2 mo)
- full control-head and chest off ground using arm in prone (3 mo)
- maximum control-can elevate in supine by lifting head (5 mo)
rolling
- earliest pattern of voluntary locomotion
- requires postural control of head, neck, trunk
- enables child to obtain position for crawling/creeping
- head turns, followed by shoulders, trunk, hips
- sequence: 1. side to back (2 mo) 2. supine to side and prone to side (4 mo) 3. supine to prone (6 mo) 4. prone to supine (8 mo)
- affordances: toys (children roll towards them), rate limiters: postural control and strength
sitting
-requires basic rolling ability and support reactions (i.e. parachute reflex)
-influences hand reaching (5-8mo)-non sitters less accurate and use 2 hands more often. all infants are more accurate sitting than supine
-sequence:
A. while supported, can sit w/ head steady (3-4 mo)
B. 1st attempts w/out support, forward lean (reflex stimulated to prevent falling)
C. unassisted, short time (5 mo), from prone/supine to sitting (8 mo), sitting down w/reasonable control (9 mo)
standing
- standing w/assistance-7-8 mo (1st attempts being held under armpits)
- pushing/pulling to standing-9 mo-tables and chairs are affordances
- standing unassisted-12 mo
crawling
- 1st effortful attempt at prone locomotion (6-8 mo)
- control of head, neck, and upper trunk required
- infant drags prone body with abdomen touching surface (precursor to creeping)
creeping
-slow movement on hands and knees that infants will revert back to as a speedy form of locomotion
-homolateral movement=same arm/leg, occurs first
contralateral movement=opposite arm/leg
origins of bipedalism
- endurance-greater stamina, more effective for tracking and killing prey
- increased thermoregulatory efficiency
- shift in diet (berry-picking)
- hands are freed (huge leaps in intelligence)
walking
- continually losing and regaining balance while moving forward in a upright position
- independent walking achieved @ 10-15 mo (possible predictor is mm mass at 6 months-larger delays acquisition)
- mature pattern walking at 4-5 yrs
early walking
- wide base of support
- flat-footed, toes turned out
- minimal ankle movement
- high guard position-limbs do not swing
