Multi-Frequency Impedance Myography: The PhaseX Effect

Abstract

Muscle contraction is often detected via EMG in prosthetics. However, signal disturbances due to electrode motions can lead to misinterpretations. Therefore, alternative measurement approaches are desired to increase the reliability of the results. In this work, a novel approach based on impedance myography is proposed. By means of an equivalent circuit of a muscle, its electrical characteristics during contractions are analyzed. In this analysis, a new biomedical marker named the PhaseX Effect is described. This effect is based on the specific behavior of the phase response when the muscle is contracted and is interesting due to its high signal robustness and low signal processing requirements. The resilience of this effect against electrode motion is also analyzed. Measurements of the complex impedance myography spectra are performed on the forearms of three subjects during relaxation and contraction of the corresponding muscle. The subject measurements show the expected behavior of the muscle model. Actual muscle contractions can easily be detected via a simple analysis of the phase response. For a better visualization, the measurements are repeated while acquiring a synchronized video of the moving forearm. The particular effect of the phase response during muscle contraction can be used as a new marker that can be beneficial in several applications such as prostheses control. The PhaseX Effect has high reliability and low signal processing requirements, making it advantageous over other muscle activity markers. The combination of a reliable marker and simple signal analysis promises to become a new method for prostheses control.

A Bioimpedance Spectroscopy Interface for EIM Based on IF-Sampling and Pseudo 2-Path SC Bandpass $\Delta\Sigma$ ADC

“…Furthermore, a noticeable phase shift and increase of the phase peak also occurs in the phase spectrum while contracting the muscle. These results are consistent with previous demonstrations of EIM during muscle contractions employing high-accuracy bio-Z spectroscopy equipment [11].…”

“…1: Illustration of EIM measurement. of muscle contractions [10], [11] and has been proposed as a biomarker for NMDs, such as amyotrophic lateral sclerosis and duschenne muscle dystrophy [12], [13].…”

“…Moreover, to diagnose neuromuscular disorders, bio-Z errors below 1% are typically required [18]. Furthermore, it has been demonstrated that muscle contractions, which happen in the 0.1 Hz to 2-10 Hz bandwidth [19], [20], can be detected in two ways: i) single-frequency multi-channel EIM, by measuring relative bio-Z magnitude and phase changes of all channels [10], [21], ii) multi-frequency single-channel EIM, by measuring phase shifts in the bio-Z spectrum [11]. Both approaches require relatively high data throughputs.…”

Comparative Study of Measurement Methods for Embedded Bioimpedance Spectroscopy Systems

“…Impedance measurement systems have been developed for a variety of applications, including material characterization with inductive sensors [ 2 ], chemical parameters investigation [ 3 ], and characterization of biological tissues [ 4 , 5 ]. Impedance spectroscopy can be applied to monitor human activity [ 6 ], diagnose muscles [ 7 ], detect and characterize cancer [ 8 ], and monitor human health on a daily basis [ 9 ]. In this case, it is called bioelectrical impedance spectroscopy (BIS) [ 5 ], which is the main focus of this paper.…”

“…In the same direction, based on the IQ demodulation technique, Hernánder et al proposed a completed BIS device for body composition estimation with a sophisticated calibration method for better measurement accuracy [ 17 ]. From another perspective, Kusche et al evaluate the potential of BIS measurement for hand gestures recognition based on novel extracted features [ 6 ].…”