Lower limb muscle responses by transcranial magnetic stimulation-evoked KNEE extension using mechanomyography / Zafirah Zakaria

Zafirah , Zakaria (2024) Lower limb muscle responses by transcranial magnetic stimulation-evoked KNEE extension using mechanomyography / Zafirah Zakaria. Masters thesis, Universiti Malaya.

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Abstract

Mechanomyography (MMG) and transcranial magnetic stimulation (TMS) are two non-invasive techniques that measure the mechanical responses of skeletal muscles and stimulate the motor cortex, respectively. Combining these methods can provide a more comprehensive understanding of the relationship between neural pathways and the muscular system, with potential applications in rehabilitation and the development of new treatments for muscle-related disorders. The primary objective of this study was to investigate whether specific motor control points in the motor cortex are necessary to generate a significant MMG peak amplitude (the maximum amplitude) that can produce functional muscle contractions leading to movement. Additionally, we aimed to analyze the relationship between TMS intensity and mechanical muscle output by analyzing the MMG mean peak amplitude and knee extension angle produced. Fourteen participants with no known neuromuscular or cognitive disorders underwent TMS with varying stimulation locations and intensities at a resting state throughout. This study found that specific point mapping of TMS locations did not produce significantly different muscle output compared to localization mapping, indicating that the location of motor control stimulation during TMS may not need to be specific to produce significant muscle outcomes. Despite the absence of voluntary contraction during the TMS procedure, MMG Mean Peak Amplitude increased with TMS intensity, and a specific threshold was identified at which the MMG Mean Peak Amplitude is significant and knee extension movement is present. This indicates that TMS can activate a sufficient number of motor neurons to produce a measurable mechanical response by the muscles, supporting the use of TMS for investigating the relationship between muscle output and joint angle during movement. This study also investigated whether there were differences in MMG Mean Peak Amplitude and knee angle responses to TMS-evoked contractions between active and sedentary groups, as well as between male and female participants. We found out that active participants and males had a lower threshold for TMS to produce a significant mechanomyography response, likely due to greater cortical excitability in these groups. Overall, the findings suggest that TMS with mechanomyography has potential implications for the development of innovative approaches in studying and enhancing muscle function, particularly in individuals with neuromuscular disorders. By providing a direct measure of muscle output, mechanomyography can help quantify the effectiveness of motor rehabilitation programs. This study contributes to the understanding of the underlying mechanisms of muscle contraction and the use of TMS with mechanomyography in clinical settings.

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