Center of Mass Acceleration Feedback Control of Standing Balance by Functional Neuromuscular Stimulation against External Postural Perturbations

IEEE Trans Biomed Eng, 2013 · DOI: 10.1109/TBME.2012.2218601 · Published: January 1, 2013

Spinal Cord Injury Rehabilitation Biomedical

Simple Explanation

This study aimed to improve standing ability in individuals with spinal cord injury (SCI) using electrical stimulation of muscles (FNS). It explored using center of mass (COM) acceleration feedback to control the stimulation, reducing reliance on upper body support. The COM acceleration, reflecting overall body movement, was measured using sensors on the pelvis and torso. The stimulation was adjusted based on this feedback to counteract disturbances and reduce the need for upper extremity support. The system's effectiveness was tested by applying external pushes and pulls to the participant and measuring how much she needed to use her arms for balance. The results showed that the feedback control reduced the arm support needed compared to constant stimulation.

Study Duration

Not specified

Participants

One 54 year-old, female with T4 level complete paraplegia

Evidence Level

Level 4, Case Study

Key Findings

1
Total body COM acceleration was accurately estimated (> 89% variance explained) using three-dimensional (3-D) outputs of two accelerometers mounted on the pelvis and torso.
2
Compared to constant muscle stimulation employed clinically, feedback control of stimulation reduced UE loading by 33%.
3
The triceps surae, tibialis anterior, erector spinae, and rectus femoris groups had higher contributions to controller responses for disturbances in the AP dimension.

Research Summary

This study investigated the use of center of mass (COM) acceleration feedback for improving performance of a functional neuromuscular stimulation (FNS) control system to restore standing function to a subject with complete, thoracic-level spinal cord injury (SCI). Compared to constant muscle stimulation employed clinically, feedback control of stimulation reduced UE loading by 33%. Future developments in FNS feedback control systems may expand testing to functional reaching tasks and consider incorporation of select joint feedback.

Practical Implications

Reduced Upper Extremity Loading

The COM acceleration feedback system reduces the reliance on upper extremities for maintaining balance during standing, potentially reducing fatigue and improving functional use of hands and arms.

Comprehensive 3-D Control

The system provides a basis for comprehensive control synergy about a global, dynamic variable, allowing for improved balance posture regulation in three-dimensional space.

Minimal Instrumentation

The system requires minimal instrumentation, making it more feasible for clinical deployment compared to systems relying on joint kinematics feedback.

Study Limitations

1
This single-case study did serve our primary objective to initially evaluate this approach under live experimental conditions from its conception and validation in simulation.
2
No significant reduction was observed for perturbations in the backward direction.
3
Muscle fatigue was not as significant for our particular subject and the issue was beyond the design scope of this study.

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