Gift of Touching - Coordinated Reaching and Contact

Goal-directed skilled movement encompasses more than just transitions in posture, or use of various reflexes. We call this section "touching" in honor of those early first goal-directed neuromotor movement experiences performed by infants, exploratory activities that quickly evolve into two-way shared experiences between individuals and between an individual and their environment. An infant starts with a reach that is really a transition in posture and a grasp that is largely reflexive (and painful for fathers with beards). But soon a new level of function emerges: trajectory planning, multi-segmental coordination (e.g., between torso, arm, hand, head and eyes) that include fundamental "motor patterns" (e.g., proximal-distal movement sequencing) and use of muscle synergies or task templates, and finally the formation of skills or motor programs. While the basic stages of motor development in children have been well documented through careful observation, our scientific knowledge of internal mechanisms remains limited.

This section focuses on the more narrow topic of the conceptual role of biomechanics and muscles synergies in skill development, especially as related to neurorehabilitation. There are several reasons why the neurorehabilitation field cares about developmental stages. One is that with neural trauma, it is well documented that motor activity normally associated with stages of motor development are often expressed: certain reflexes, for example.

Dynamics of Movement

• Beyond Posture: Inertial Dynamics
  • Tangential, centripetal, coriolis components
• Redundancy
  • Kinematic - more "joint DOFs" than end-point coordinates
  • Actuator - more muscle motors than necessary to rotate all joint DOFs
• Changes with Environmental Contact
• "Motor Programs" that "Learn" and Thus "Know" Dynamics?

Synergies and Neuromotor Developmental Stages

• Brain Sensorimotor Structures: More Redundancy, and Synergy Patterns
• Stages of Motor Development: Motor Patterns and Skill Acquisition
• Examples:
  • Stages of walking and the "Central Pattern Generator"
  • Stages of power throwing/striking: proximal-to-distal sequencing
    • "learning mechanics"
    • taking advantage of muscle properties (higher force during lengthening, stretch-shortening cycle, turning antagonistic muscles off)
  • Stages of Goal-Directed Arm Movements
    • single-joint: antagonistic pulse strategies, speed-accuracy tradeoffs
    • multilink: reaching/whipping
    • adding in coordinated grasping

Performance Assessment and "Performance Criteria"

• Goal-Direct Behavior
• Scaling Strategies for Dynamic Movements

Disability Challenges and Accommodations (Neurorehab Focus)

• General Principles of Neurorehab for Skill Acquisition
• Stable Mobility (e.g., Walking)
• Stable Manipulation (e.g., Reaching/Grasping)
• Examples: Challenges of Functional Neuromuscular Stimulation Systems
  • Lower Extremity: Standing and Walking
  • Upper Extremity: Reaching, Grasping and Manipulation

| gift-touching | movement dynamics | movement synergies | performance | disability/access |