Wearable exoskeleton control modes selected during overground walking affect muscle synergies in adults with a chronic incomplete spinal cord injury

Spinal Cord Series and Cases, 2020 · DOI: https://doi.org/10.1038/s41394-020-0269-6 · Published: March 10, 2020

Spinal Cord Injury Assistive Technology Rehabilitation

Simple Explanation

This study looks at how different control modes of wearable robotic exoskeletons (WRE) affect muscle coordination during walking in people with incomplete spinal cord injury (iSCI). Muscle coordination is assessed by looking at muscle synergies (MSs), which are patterns of muscle activation. The study found that a specific control mode called HASSIST, which allows for free leg movement but provides assistance, best replicated the muscle coordination patterns seen in able-bodied individuals during walking. The findings suggest that the choice of WRE control mode can influence how effectively individuals with iSCI can relearn to walk with typical muscle coordination.

Study Duration

2 weeks

Participants

Three participants with chronic iSCI (ASIA Impairment Scale, AIS = C or D)

Evidence Level

Case series

Key Findings

1
Walking with a WRE in control modes allowing step variability (i.e., self-selected trajectory), and assisting L/E swing phase (i.e., HASSIST), best replicated MSs observed in able-bodied individuals during overground walking, while requiring light to moderate effort.
2
The HASSIST mode consistently replicated the number of MSs and weight of muscles composing each MS in the reference able-bodied individual.
3
Most WRE control modes did not replicate the motor control required for typical L/E muscle coordination during stereotypical overground walking.

Research Summary

This case series examined how different WRE control modes influence lower extremity muscle synergies in individuals with iSCI during overground walking. The study compared trajectory-controlled (TOT, ADAPT) and non-trajectory-controlled (HASSIST, HRESIST, NEUTRAL) modes. The key finding was that the HASSIST mode, which provides assistance within a self-selected lower extremity trajectory, best replicated muscle synergies in able-bodied controls during overground walking. The authors conclude that the results highlight the importance of understanding the effects of various control modes on lower extremity motor control to inform clinical practice in WRE locomotor interventions.

Practical Implications

Clinical Practice

The study suggests that HASSIST mode could be a preferred mode for promoting typical muscle coordination during WRE-assisted walking in individuals with iSCI.

Rehabilitation Programs

The findings highlight the need to personalize WRE-based rehabilitation interventions to maximize locomotion and locomotion-related abilities based on the effects of different control modes.

Future Research

The study calls for additional research with more robust experimental designs and larger sample sizes to strengthen evidence and further support clinical decision-making when aiming to improve lower extremity motor control during walking.

Study Limitations

1
Small sample size of adults with a chronic iSCI, limiting generalization of the results.
2
Lack of kinematic analysis makes it difficult to determine to what extent WRE movement strategies were similar to those established for overground walking.
3
The actual absolute level of assistance or resistance provided by the WRE remains unknown.

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