Sonomechanomyography (SMMG): Mapping of Skeletal Muscle Motion Onset during Contraction Using Ultrafast Ultrasound Imaging and Multiple Motion Sensors

Abstract

Background: Available methods for studying muscle dynamics, including electromyography (EMG), mechanomyography (MMG) and M-mode ultrasound, have limitations in terms of spatial resolution. Methods: This study developed a novel method/protocol of two-dimensional mapping of muscle motion onset using ultrafast ultrasound imaging, i.e., sono-mechano-myo-graphy (SMMG). The developed method was compared with the EMG, MMG and force outputs of tibialis anterior (TA) muscle during ankle dorsiflexion at different percentages of maximum voluntary contraction (MVC) force in healthy young adults. Results: Significant differences between all pairwise comparisons of onsets were identified, except between SMMG and MMG. The EMG onset significantly led SMMG, MMG and force onsets by 40.0 ± 1.7 ms (p < 0.001), 43.1 ± 5.2 ms (p < 0.005) and 73.0 ± 4.5 ms (p < 0.001), respectively. Muscle motion also started earlier at the middle aponeurosis than skin surface and deeper regions when viewed longitudinally (p < 0.001). No significant effect of force level on onset delay was found. Conclusions: This study introduced and evaluated a new method/protocol, SMMG, for studying muscle dynamics and demonstrated its feasibility for muscle contraction onset research. This novel technology can potentially provide new insights for future studies of neuromuscular diseases, such as multiple sclerosis and muscular dystrophy.

Modulations in motor unit discharge are related to changes in fascicle length during isometric contractions

“…This assessment, however, assumes that there is no lag between the generation of a contraction and the transmission of force to the tendon. More recent studies that have combined conventional bipolar EMG and ultrasound during voluntary contractions have found that fascicle shortening happen before force/torque is generated (Begovic et al , 2014; Ling et al , 2020), which agrees with our findings. Nevertheless, this assessment has several issues, first, the onset of muscle activation from bipolar EMG signals can be greatly influenced by the electrode’s location (Hug et al , 2011), second, fascicle shortening from deeper muscle regions could happen before EMG activity is detected on the surface (Dieterich et al , 2017) and third, the assessment can be confounded by the mechanical impedances of the measuring device (Corcos et al , 1992).…”

“…Similar to the current study, this previous research also revealed that fascicle shortening happens before force/torque is measured (3,34,58). However, the magnitude of these delays is considerably smaller than the ones presented herein, with ~6ms (EMG-FL) and ~12ms (EMGforce) of delay for electrically-induced contractions (34,44) and ~29ms (EMG-FL) and ~50ms…”

“…Due to many factors such as crosstalk, amplitude cancellation and underlying changes in muscle length and velocity, surface EMG amplitude is unfortunately poorly correlated with the resultant force produced by muscles and therefore cannot be used to directly understand the neural determinants of muscle contractions (16,17,42). Furthermore, studies that have examined changes in muscle architecture directly using ultrasound (3,11,29,34) do not often image from the same region as where the EMG is collected (57). Therefore, changes in muscle architecture and/or morphology from nearby or other regions could potentially provide results that are not related from those studied from the region of interest.…”

How Does Lower Limb Respond to Unexpected Balance Perturbations? New Insights from Synchronized Human Kinetics, Kinematics, Muscle Electromyography (EMG) and Mechanomyography (MMG) Data

“…The onset and peak points of various signals were identified within 2 s after the start of balance perturbation. The onset time of body CoM, body CoP, joint angle, joint moment, joint power, muscle EMG, and muscle MMG data was defined as the first time point when the corresponding normalized signal/data value went beyond five times of the standard deviation (SD) from the baseline value (mean + 5SD) [ 40 ]. The baseline value was calculated as the mean over the 1000-ms interval before the start of balance perturbation.…”

Mapping of Back Muscle Stiffness along Spine during Standing and Lying in Young Adults: A Pilot Study on Spinal Stiffness Quantification with Ultrasound Imaging

“…More recently, the non-invasive and real-time ultrasound shear-wave elastography (SWE) has become a popular and useful tool for assessing muscle stiffness [ 23 , 24 ]. For this technology, the ultrasound probe can induce a focused acoustic force and create a shear wave within the target tissue [ 25 , 26 ]. By capturing the propagation of the shear wave, the speed of the shear wave propagation (c) can be calculated, which can then be squared and multiped by three and the muscle mass density (ρ = 1000 kg/m 3 ) to calculate the muscle elasticity (assumed as E = 3ρc 2 ) [ 25 ].…”