Yuya SUZUKI, Kazuhiro MATSUI, Keita ATSUUMI, Kazuhiro TANIGUCHI, Hiroaki HIRAI, Atsushi NISHIKAWA
Vol. 13 (2024) p. 205-213

With recent advancements in human digital twin study, acquiring human neuromuscular characteristics has become a dire necessity. However, many of these studies use large equipment for imaging, such as computed tomography, and are not suitable for conducting clinical screening examinations. Evoked electromyography (eEMG) and manual muscle testing (MMT) are some of the simple clinical examination methods for acquiring human neuromuscular characteristics. The eEMG method is used to examine neural transmission functions. This method involves electrically stimulating nerves and analyzing the compound action potentials obtained from the muscles. However, it can only identify the time delay in the neuromuscular system. Alternatively, MMT is a simple testing method that can only obtain static muscle-force characteristics. Other methods to obtain muscle dynamic characteristics do not consider multiple muscle coordination. In this study, we developed a method to acquire the dynamics of human wrist-joint neuromuscular systems as a second-order and time delay system for clinical screening examinations. This method applies functional electrical stimulation (FES) to agonist-antagonist muscle pairs and achieve isometric force-sensing. The parameters of this dynamic system are indicators of the neuromuscular characteristics of this dynamic system. We confirmed the possibility of using these indicators for clinical examinations. The results suggest that the damping ratio is reproducible and can be applied to the clinical test, particularly for sarcopenia. However, further studies are needed to expand the frequency range of the input FES wave and examine the change of optimization method to fit the transfer function for system identification. In addition, a further study with a larger sample size is needed after strictly defining and recruiting the subject group.