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BioMed Research International
Volume 2017, Article ID 9469548, 16 pages
Research Article

Age and Sex Effects on the Active Stiffness of Vastus Intermedius under Isometric Contraction

1Paul C. Lauterbur Research Center for Biomedical Imaging, Institute of Biomedical and Health Engineering, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
2Interdisciplinary Division of Biomedical Engineering, the Hong Kong Polytechnic University, Hong Kong
3School of Biomedical Engineering, Shenzhen University, Shenzhen, China

Correspondence should be addressed to Yongjin Zhou; nc.ude.uzs@uohzjy

Received 5 August 2016; Revised 30 October 2016; Accepted 16 March 2017; Published 3 April 2017

Academic Editor: Hiroshi Tanaka

Copyright © 2017 Cong-Zhi Wang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Previously, a novel technique was proposed to quantify the relationship between the muscle stiffness and its nonfatigue contraction intensity. The method extended the measured range of isometric contraction to 100% maximum voluntary contraction (MVC) using an ultrasonic shear wave measurement setup. Yet, it has not been revealed how this relationship could be affected by factors like age or sex. To clarify these questions, vastus intermedius (VI) stiffness of 40 healthy subjects was assessed under 11 step levels of isometric contraction. The subjects were divided into four groups: young males, young females, elderly males, and elderly females ( for each). In a relaxed state, no significant difference was observed between the male and female subjects () nor between the young and elderly subjects (). However, when performing isometric contraction, the VI stiffness of males was found to be significantly higher than that of females at the same level (), and that of the young was higher than the elderly (). Meanwhile, for two knee joint angles used, the stiffness measured at a 90° knee joint angle was always significantly larger than that measured at 60° (). Recognizing the active muscle stiffness of VI contributes to body stability, and these results may provide insight into the age and sex bias in musculoskeletal studies, such as those on fall risks.