Supplemental Figures for Enhanced M-wave Localization via HD-sEMG

This study evaluates high-density surface electromyography (HD-sEMG) combined with peripheral nerve stimulation and ultrasound imaging for isolating M-waves in the forearm muscles. This repository contains supplemental figures that support the findings described in the study, providing additional visual data for readers.

Fig. S1. Muscle anatomy map of Subject 1. Muscle anatomy maps using the monopolar (a) and tripolar (b) montage during the highest stimulation of the median, ulnar, and radial nerves. From left to right, HD-sEMG grids were placed on the ulnar, anterior, and posterior forearm. We marked grids expected to show muscle recruitment based on nerve stimulation with a magenta outline. We normalized peak-to-peak amplitudes, and ultrasound imaging identified muscles associated with each hotspot. 

Fig. S2. Muscle anatomy map of Subject 2. Muscle anatomy maps using the monopolar (a) and tripolar (b) montage during the highest stimulation of the median, ulnar, and radial nerves. From left to right, HD-sEMG grids were placed on the ulnar, anterior, and posterior forearm. We marked grids expected to show muscle recruitment based on nerve stimulation with a magenta outline. We normalized peak-to-peak amplitudes, and ultrasound imaging identified muscles associated with each hotspot. 

Fig. S3. Muscle anatomy map of Subject 3. Muscle anatomy maps using the monopolar (a) and tripolar (b) montage during the highest stimulation of the median, ulnar, and radial nerves. From left to right, HD-sEMG grids were placed on the ulnar, anterior, and posterior forearm. We marked grids expected to show muscle recruitment based on nerve stimulation with a magenta outline. We normalized peak-to-peak amplitudes, and ultrasound imaging identified muscles associated with each hotspot. 

Fig. S4. Muscle anatomy map of Subject 4. Muscle anatomy maps using the monopolar (a) and tripolar (b) montage during the highest stimulation of the median, ulnar, and radial nerves. From left to right, HD-sEMG grids were placed on the ulnar, anterior, and posterior forearm. We marked grids expected to show muscle recruitment based on nerve stimulation with a magenta outline. We normalized peak-to-peak amplitudes, and ultrasound imaging identified muscles associated with each hotspot. 

Fig. S5. Muscle anatomy map of Subject 5. Muscle anatomy maps using the monopolar (a) and tripolar (b) montage during the highest stimulation of the median, ulnar, and radial nerves. From left to right, HD-sEMG grids were placed on the ulnar, anterior, and posterior forearm. We marked grids expected to show muscle recruitment based on nerve stimulation with a magenta outline. We normalized peak-to-peak amplitudes, and ultrasound imaging identified muscles associated with each hotspot. 

Fig. S6. Muscle action potential propagation. We present data from Subject 2 at the highest stimulation intensity for the (a) monopolar, (b) bipolar, and (c) tripolar montages (0 to 30 ms post-stimulation). Correlation of adjacent waveforms (mean ± standard deviation across electrodes) was higher in the monopolar montage compared to the bipolar and tripolar montages. Red arrows indicate the direction of muscle action potential propagation, originating from the innervation zone where the nerve activates the muscle. (red asterisks). Propagation was absent in the monopolar montage. Time adjustment in the bipolar (d) and tripolar (e) montages substantially increased waveform correlation, confirming that muscle action potential propagation contributed to lowering waveform correlation. The bottom electrode in each pair was time adjusted (red).