Measurement of muscle contraction with ultrasound imaging

TLDR

The study aimed to determine whether ultrasonography can estimate muscle activity by measuring architectural parameters during isometric contractions from 0 to 100 % MVC. Researchers measured pennation angles, fascicle lengths, and muscle thickness of several human muscles during isometric contractions and simultaneously recorded electromyographic activity with surface or fine‑wire electrodes. Ultrasound detected low‑level muscle activity but could not distinguish moderate from strong contractions; it reliably identified EMG changes as low as 4–9 % MVC in specific muscles, detected abdominal contractions at 12–22 % MVC, yet failed to consistently measure obliquus externus thickness, indicating it is a noninvasive method for detecting isometric contractions in certain muscles. Muscle Nerve 27: 682–692, 2003.

Abstract

Abstract To investigate the ability of ultrasonography to estimate muscle activity, we measured architectural parameters (pennation angles, fascicle lengths, and muscle thickness) of several human muscles (tibialis anterior, biceps brachii, brachialis, transversus abdominis, obliquus internus abdominis, and obliquus externus abdominis) during isometric contractions of from 0 to 100% maximal voluntary contraction (MVC). Concurrently, electromyographic (EMG) activity was measured with surface (tibialis anterior only) or fine‐wire electrodes. Most architectural parameters changed markedly with contractions up to 30% MVC but changed little at higher levels of contraction. Thus, ultrasound imaging can be used to detect low levels of muscle activity but cannot discriminate between moderate and strong contractions. Ultrasound measures could reliably detect changes in EMG of as little as 4% MVC (biceps muscle thickness), 5% MVC (brachialis muscle thickness), or 9% MVC (tibialis anterior pennation angle). They were generally less sensitive to changes in abdominal muscle activity, but it was possible to reliably detect contractions of 12% MVC in transversus abdominis (muscle length) and 22% MVC in obliquus internus (muscle thickness). Obliquus externus abdominis thickness did not change consistently with muscle contraction, so ultrasound measures of thickness cannot be used to detect activity of this muscle. Ultrasound imaging can thus provide a noninvasive method of detecting isometric muscle contractions of certain individual muscles. Muscle Nerve 27: 682–692, 2003