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Updated: May 10, 2026
07:25
An Objective and Child-friendly Assessment of Arm Function by Using a 3-D Sensor
Published on: February 12, 2018
Invariant geometric characteristics of spatial arm motion
Satyajit Ambike1, James P Schmiedeler
1Department of Kinesiology, The Pennsylvania State University, University Park, PA, USA. ssa.17@psu.edu
Experimental Brain Research
|June 18, 2013
Summary
This study reveals wrist paths in reaching movements tend to be planar and curve more at slower speeds. Wrist speed profiles deviate from the typical bell shape for slow, long movements.
Area of Science:
- Biomechanics
- Motor Control
- Human Movement Analysis
Background:
- Conflicting data exists on the time invariance of wrist path shape in reaching movements.
- Previous analyses often focus on second-order geometric properties like curvature, neglecting higher-order properties.
Purpose of the Study:
- To investigate third-order geometric properties of wrist path and first-order wrist speed during spatial pointing.
- To analyze how movement speed affects wrist path shape and orientation.
Main Methods:
- Subjects performed point-to-point reaching movements in a 3D workspace.
- Movement kinematics were recorded using electromagnetic sensors on the arm and thorax.
- Analysis focused on geometric properties (planarity, torsion) and speed profiles.
Main Results:
- Wrist paths demonstrated planarity (near-zero torsion) and increased curvature with decreased speed.
- The orientation of the wrist path plane was task-dependent but speed-invariant.
- Wrist speed profiles exhibited multiple peaks in slow, long movements, diverging from the bell-shaped profile.
Conclusions:
- Wrist paths in reaching movements are predominantly planar, with curvature influenced by speed.
- Deviations in wrist speed profiles challenge existing models for slow, prolonged movements.
- Findings offer insights into motor control strategies during human arm movements.
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