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Updated: Jul 15, 2026
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An Objective and Child-friendly Assessment of Arm Function by Using a 3-D Sensor
Published on: February 12, 2018
Toy-oriented changes in early arm movements II--joint kinematics.
A N Bhat1, H M Lee, J C Galloway
1Infant Motor Behavior Laboratory, Department of Physical Therapy, Mckinly Lab, Biomechanics and Movement Science Program, University of Delaware, Newark, DE 19716, USA.
Infant Behavior & Development
|April 3, 2007
Summary
Infants show distinct changes in arm and joint movements when a toy is present, even before purposeful reaching develops. These toy-oriented movements evolve through Early, Mid, and Late phases, highlighting the role of spontaneous movements in motor development.
Area of Science:
- Developmental motor control
- Infant kinematics
- Early motor development
Background:
- Infants exhibit 'toy-oriented' changes in hand kinematics months before purposeful reaching.
- These kinematic changes occur in distinct Early, Mid, and Late phases.
Purpose of the Study:
- To investigate toy-oriented changes in joint kinematics in infants.
- To test hypotheses regarding the evolution of joint movements in response to a toy.
Main Methods:
- Longitudinal observation of 13 infants from 8 to 20 weeks.
- High-speed motion analysis of arm movements with and without a toy.
Main Results:
- Early phase: infants scaled down movements.
- Mid phase: infants scaled up movements, showing increased shoulder flexion/adduction.
- Late phase: infants increased shoulder excursion and speed relative to the elbow, aligning with hand kinematics.
Conclusions:
- Toy-oriented changes in joint kinematics parallel hand kinematic development.
- Reaching development involves shoulder-elbow dissociation and speed-amplitude relationships.
- Spontaneous movements play a crucial role in the development of reaching.
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