Lifespan RGM

Independent sitting (6 months)

Major postural milestone enabling improved reaching and object tracking.

Crawling onset

Typically emerges around 6 months as gross motor control improves.

Pull to stand (1 year)

Indicates improved lower‑extremity strength and postural control.

First steps (1 year)

Marks transition to upright mobility and increased UE freedom.

Walking (2 years)

Independent, efficient gait pattern begins to stabilize.

Stairs (3 years)

Child can ascend/descend with alternating steps.

Single‑leg stance 3 seconds (3 years)

Early balance milestone.

Single‑leg stance 10 seconds (4 years)

Indicates improved postural stability.

Single‑leg hop (4 years)

Requires strength, balance, and coordination.

Four components of RGM

Locating target, transporting limb, grasping, in‑hand manipulation.

Grasp reflex

Present from birth to ~6 months; involuntary palmar grasp.

ATNR

Present 0–6 months; may interfere with early reaching.

Locating objects at birth

Present; infants visually orient to stimuli.

Arm transport at birth

Present but poorly controlled.

Grasp development onset

Begins around 4–5 months.

Fisted grasp (6 weeks)

Early crude grasp pattern before finger extension emerges.

Smooth pursuit onset

Begins around 6 weeks; improves rapidly.

Predictive tracking (5 months)

Infant anticipates object movement.

Visually guided reach

Dominant strategy until ~7 months.

Head control before reach

Stable head control emerges weeks before reaching begins.

Trunk stability (4 months)

Provides stable base for reaching.

Bernstein’s theory in infants

Shoulder dominates early reach; elbow contribution increases by 6 months.

Bimanual mirrored reaching

Common early pattern; unilateral reach dominates by 6 months.

Reflexive grasp at birth

Controlled by tactile and proprioceptive reflexes.

Feedforward grasp (5 months)

Present but immature; refined with age.

No in‑hand manipulation (first 6 months)

Fine motor control not yet developed.

STNR (6–12 months)

Present but minimally limits reaching due to improved head control.

Pincer grasp emergence

Appears around 9–10 months.

Sitting improves tracking

Independent sitters track moving objects more effectively.

Cephalocaudal development

Trunk control improves reach efficiency.

Proprioceptive use in reach

Begins after 7 months as reliance on vision decreases.

Hand opening proportional to object

Emerges 6–12 months as anticipatory control improves.

Fractionated finger movements

Develop during late infancy; essential for precision grasp.

12–18 month fine motor skills

Uses spoon, turns pages, waves, pincer grasp refined.

18‑month fine motor skills

Builds 2–3 block tower, scribbles with power grasp.

18–24 month fine motor skills

Builds 4–6 block tower, throws ball, uses knife for soft foods.

2+ year hand differentiation

Begins using bimanual tasks like cutting.

3–4 year catching

Can catch a bouncing ball.

Reach 1–4 years

Smoother trajectories, consistent interjoint coordination.

Grasp 1–4 years

Rapid refinement; anticipatory force modulation improves.

Crude in‑hand manipulation

Present by 3–4 years; progresses toward tripod grasp.

Gross motor skills at 4–11 years

Throwing, catching, swinging, jump rope.

Fine motor skills at 4–11 years

Improved writing, drawing, typing, crafting.

Reach 4–11 years

Gradual improvements; temporary regression around age 7.

Feedforward grasp (4–5 years)

Primary strategy with minimal somatosensory feedback.

Feedforward/feedback balance (5–6 years)

Equal reliance for grip control.

In‑hand manipulation development

Rapid from ages 3–7.

Adult‑level reach/grasp

Achieved around age 11.

Adult‑level dual‑task RGM

Achieved around age 15.

Adult‑level reaction time

Achieved around age 16–17.

Volitional reaching (2 months)

Early intentional arm movement.

Extended arms in prone (6 months)

Supports early reaching and weight‑bearing.

Crawling (7–9 months)

Improves UE strength and coordination.

Creeping and pull‑to‑stand (10–12 months)

Major gross motor milestones.

Overhand throw (18–24 months)

Requires UE coordination and trunk rotation.

Tripod grasp (3–4 years)

Mature pencil grasp pattern.

In‑hand manipulation (5–7 years)

Improves with increased sensory feedback use.

Ball interception (15 weeks)

Infant can intercept but not grasp.

Ball trapping (12 months)

Traps rolled ball using body.

Chest‑trap catch (2 years)

Uses arms and trunk.

Outstretched arm catch (3 years)

Improved timing and coordination.

Hand‑only catch (4–6 years)

Can catch small or fast balls.

Hand‑eye coordination (5–6 years)

Mature catching of smaller balls.

Practice‑dependent skill differences

Experience drives variability in RGM performance.

Aging MSK changes

Distal > proximal weakness, more type I fibers, ROM loss.

Aging neuromuscular changes

Increased visual reliance, co‑contraction, larger motor units, decreased NCV.

Aging reach — MSK

Slowest reach of any age group; reduced postural control.

Aging grasp — MSK

Decreased grip strength.

Aging reach — NM

Low trunk stability and slowed nerve conduction.

Aging grasp — NM

Reduced precision and fine motor control.

Older adult reaching strategy

Longer deceleration phase for accuracy.

Reduced feedforward control (aging)

Due to parietal, visual, and cerebellar decline.

Increased visual reliance (aging)

Compensates for reduced proprioception and feedforward control.

Dual‑task decline (aging)

Greater interference during complex tasks.

Muscle property changes (aging)

Fewer motor units, reduced force modulation.

Postural stability decline (aging)

Leads to less steady reaching.

Tactile sensation decline (aging)

Reduced cutaneous input after age 60.

In‑hand manipulation decline (aging)

Reduced dexterity and precision.

Precision grip decline (aging)

Reduced ability to modulate grip force.

High‑complexity task decline (aging)

Greater loss than in basic ADLs.

Strength training benefits (aging)

Improves grip performance.

Eye‑hand coordination training

Can improve reaction time, even more than in younger adults.

Video game training

Enhances visuomotor speed and coordination.

Dual‑task training (aging)

Requires longer practice to improve.