Comparing joint kinematics and center of mass acceleration as feedback for control of standing balance by functional neuromuscular stimulation

Journal of NeuroEngineering and Rehabilitation, 2012 · DOI: 10.1186/1743-0003-9-25 · Published: May 6, 2012

Simple Explanation

This study explores different ways to control standing balance using electrical stimulation for people with spinal cord injury (SCI). It looks at using information about joint movements (joint kinematics) or the body's center of mass acceleration (COM) to adjust the stimulation. The study used computer simulations to compare these two control methods, along with a combination of both. They measured how much effort was needed from the upper body to maintain balance when the person was pushed or disturbed. The results suggest that using COM acceleration might be a better approach because it is more reliable and requires fewer sensors. Pilot data from a person with SCI also supports this idea.

Study Duration

Not specified

Participants

One female subject with complete thoracic-level (T4) SCI

Evidence Level

Level III; Simulation and pilot data from a single subject with SCI

Key Findings

1
Compared to constant stimulation, feedback control systems using joint kinematics, COM acceleration, or a combination reduced the need for upper extremity support by 51%, 43%, and 56%, respectively.
2
COM acceleration feedback was more robust to sensor tracking errors compared to joint kinematics feedback, with performance degradation of 35% versus 86% at typical error levels.
3
Pilot data indicated that COM acceleration could be estimated with a few well-placed sensors and efficiently captures information related to movement synergies during perturbed standing following SCI.

Research Summary

This study compared the effectiveness of joint kinematics and center of mass (COM) acceleration feedback for controlling standing balance using functional neuromuscular stimulation (FNS) in individuals with spinal cord injury (SCI). Simulation results showed that both feedback methods, either alone or in combination, reduced upper extremity effort compared to constant stimulation. However, COM acceleration feedback demonstrated superior robustness to sensor errors. Pilot data from a subject with SCI suggested that COM acceleration could be effectively estimated using a limited number of sensors, making it a feasible option for clinical implementation of FNS-based standing control.

Practical Implications

Clinical Implementation

COM acceleration feedback may be a more practical solution for controlling standing with FNS due to its robustness and fewer sensor requirements.

Sensor Placement

Accelerometer measurements at the pelvis and torso may be sufficient to accurately characterize the feedback required for COM acceleration control.

Future Research

Further investigation is needed to determine an optimal combination of joint and COM acceleration inputs to improve performance while minimizing sensor requirements.

Study Limitations

1
The study used a simulation model, which may not perfectly represent real-world conditions.
2
Pilot data was collected from only one subject with SCI, limiting the generalizability of the findings.
3
The study focused on external force-pulse perturbations and may not fully capture the demands of all functional activities.

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