Evaluating the Intensity of Muscle Contraction by Near-Infrared Spectroscopy, a Potential Application for Scaling...

Area of Science:

• Biomedical Engineering
• Neuroscience
• Rehabilitation Science

Background:

• Muscle spasticity is a common challenge in neurological disorders like cerebral palsy, spinal cord injury, and multiple sclerosis.
• Current assessment methods, such as the Modified Ashworth Scale, suffer from subjective interpretation and inconsistency.
• Objective, real-time measurement of muscle contraction is needed for accurate spasticity evaluation.

Purpose of the Study:

• To evaluate near-infrared spectroscopy (NIRS) as a non-invasive tool for quantifying muscle contraction intensity.
• To determine the correlation between NIRS-derived muscle oxygenation and varying levels of voluntary muscle contraction.
• To assess the potential of NIRS for objective spasticity assessment.

Main Methods:

• Thirty-seven healthy adults participated in the study.
• Participants performed isometric contractions at 15%, 30%, 45%, and 60% of their maximal voluntary contraction.
• Near-infrared spectroscopy (NIRS) monitored Tissue Oxygenation Index (TOI) changes, while electromyography (EMG) measured muscle activity.

Main Results:

• A significant negative correlation was found between muscle contraction intensity and the change in Tissue Oxygenation Index (ΔTOI).
• Higher contraction intensities led to greater reductions in muscle oxygenation, as measured by NIRS.
• Multinomial logistic regression confirmed that TOI reliably predicted contraction intensity (p < 0.001).

Conclusions:

• Near-infrared spectroscopy (NIRS) can objectively measure muscle contraction intensity through changes in muscle oxygenation.
• This non-invasive technique provides a reliable and potentially real-time method for assessing muscle activity.
• NIRS holds promise as an objective tool to enhance spasticity assessment and inform treatment strategies.