Invasive dynamic electrical impedance myography during 100s of moderate contraction in rats' gastrocnemius muscle.

Abstract

The present study aimed to investigate the behavior of dynamic electrical impedance myography (dEIM) signals during a 100-s period of the dynamic contraction of Wistar rats' gastrocnemius evoked by electrical stimulation and to link the variations in bioimpedance with muscular energy systems. Muscle contraction used 30% of the maximum muscular force and persisted for 100s, along which dynamic bioimpedance signals were acquired. Based on the bioimpedance signals, two parameters, ΔZc and ΔZpc, were calculated to allow the analysis of their changes with the energy systems that supplied adenosine triphosphate (ATP) to the muscle. ΔZc indicated the variation of impedance of a twitch cycle compared to the values observed during the rest period preceding the cycle, and ΔZpc indicated slow bioimpedance variations compared to the values obtained during the rest period. The results indicated that ΔZc followed the force behavior, achieving a change rate of ∼14%. This parameter was associated with instantaneous impedance changes owing to the occurrence of each twitch. Although the findings of this study were linked to energy system processes, future studies are required for improving the understanding of the underlying mechanisms involved in dEIM. The results contributed to understanding the relation of energy systems that supply ATP to the muscles with dEIM variations that occurred during muscle activity.