Upper limb joint dynamics during manual wheelchair propulsion

Area of Science:

• Biomechanics
• Human movement analysis
• Rehabilitation engineering

Background:

• Inverse dynamic methods are standard for estimating joint loads in manual wheelchair propulsion.
• Interpreting 3D net joint moments and powers can be challenging.
• Joint coordinate systems and 3D angles between moment and velocity vectors aid joint dynamics understanding.

Purpose of the Study:

• To analyze upper limb joint dynamics during manual wheelchair propulsion using joint coordinate systems and 3D joint angles.
• To determine joint configurations (propulsion, resistance, stabilization) at the wrist, elbow, and shoulder.

Main Methods:

• Nine individuals with spinal cord injuries propelled an instrumented wheelchair.
• Reflective markers and inverse dynamics were used to analyze upper limb joint moments and angular velocities.
• The 3D angle between joint moment and angular velocity vectors quantified joint configuration.

Main Results:

• Wrist and elbow joints predominantly exhibited a stabilization configuration (angle near 90 degrees).
• Shoulder joints showed a propulsion configuration, nearing stabilization (angle below 60 degrees).
• Specific moments (extension, ulnar deviation, adduction, flexion, internal rotation) were identified at each joint.

Conclusions:

• Joint stabilization configurations may explain the reduced mechanical efficiency in manual wheelchair propulsion.
• Understanding these joint dynamics offers insights into potential injury risks at the wrist, elbow, and shoulder.