title: An attempt to bridge muscle architecture dynamics and its instantaneous rate of force development using ultrasonography.
abstract: Muscle force output is an essential index in rehabilitation assessment or physical exams, and could provide considerable insights for various applications such as load monitoring and muscle assessment in sports science or rehabilitation therapy. Besides direct measurement of force output using a dynamometer, electromyography has earlier been used in several studies to quantify muscle force as an indirect means. However, its spatial resolution is easily compromised as a summation of the action potentials from neighboring motor units of electrode site. To explore an alternative method to indirectly estimate the muscle force output, and with better muscle specificity, we started with an investigation on the relationship between architecture dynamics and force output of triceps surae. The muscular architecture dynamics is captured in ultrasonography sequences and estimated using a previously reported motion estimation method. Then an indicator named as the dorsoventrally averaged motion profile (DAMP) is employed. The performance of force output is represented by an instantaneous version of the rate of force development (RFD), namely I-RFD. From experimental results on ten normal subjects, there were significant correlations between the I-RFD and DAMP for triceps surae, both normalized between 0 and 1, with the sum of squares error at 0.0516±0.0224, R-square at 0.7929±0.0931 and root mean squared error at 0.0159±0.0033. The statistical significance results were less than 0.01. The present study suggested that muscle architecture dynamics extracted from ultrasonography during contraction is well correlated to the I-RFD and it can be a promising option for indirect estimation of muscle force output.
authors.affiliation: School of Medicine, Shenzhen University, China; Department of Electronic Engineering, The Chinese University of Hong Kong, Hong Kong.
authors.forename: Jizhou
authors.initials: J
authors.lastname: Li
authors.affiliation: School of Medicine, Shenzhen University, China; National-Regional Key Technology Engineering Laboratory for Medical Ultrasound, China; Guangdong Key Laboratory for Biomedical Measurements and Ultrasound Imaging, China. Electronic address: yjzhou@szu.edu.cn.
authors.forename: Yongjin
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Interdisciplinary Division of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong.
authors.forename: Yong-Ping
authors.initials: YP
authors.lastname: Zheng
authors.affiliation: Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, China.
authors.forename: Guanglin
authors.initials: G
authors.lastname: Li
mesh_terms: D000328:Adult; D004576:Electromyography; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging* / Q000502:physiology*; D019415:Torque; D014463:Ultrasonography
keywords: Image processing; Motion estimation; Muscle contraction; Rate of force development; Ultrasound