New study shows better way to easily assess knee muscle function

Muscular strength and its improvement are important to everyone for their regular day-to-day life activities. Conventionally, muscle function can be assessed by means of physical performance tests and/or muscle strength measurements. However, these methods are not applicable to those who cannot undergo forceful muscle contractions like infants, the elderly, and patients with injuries or cognitive disorders (like dementia).

An easy and popular alternative is using bioelectric impedance analysis (BIA), which can quickly and non-invasively measure tissue resistance (which depends on the amount of water and electrolytes present in the tissue) and reactance (which depends on the integrity of the cell membrane). Phase angle (PhA), a measurement derived via BIA, is calculated using the tissue’s resistance and reactance. It is directly proportional to muscle cell mass and function. Many studies have linked whole-body PhA with maximal muscle strength, but there are none associating PhA with knee extension strength or explosive muscle strength (which is the strength required to make quick, strong movements like sprinting or getting up from a chair) in adults. Keeping in mind the importance of knee muscle strength—especially in the elderly, in whom it is necessary for their independence, and athletes, who require strong knees for better performance–such a study was necessary.

In this vein, a group of scientists including Professor Ryota Akagi, from the College of Systems Engineering and Science, Shibaura Institute of Technology (SIT); Assistant Professor Kosuke Hirata from the Faculty of Sport Sciences, Waseda University; and researchers Yosuke Yamada and Tsukasa Yoshida from the Section of Healthy Longevity Research, National Institute of Health and Nutrition, National Institutes of Biomedical Innovation, Health and Nutrition investigated the association of PhA with the neuromuscular properties of knee extensor muscles in both, young and older adults. Their findings were published in Volume 13 of Frontiers in Physiology on 11 August, 2022. Dr. Akagi and Dr. Hirata, the corresponding authors of the article, tell us, “We aimed to assess the association of thigh PhA with maximal muscle strength, explosive muscle strength, contractile properties as well as neuromuscular activity, and find out which of the two—whole-body or thigh PhA–was a better predictor of knee extensor strength.”

The team measured the whole-body and thigh PhA of 55 participants (23 young males and 32 older males) at 50kHz. The participants were asked to perform 4-second maximal voluntary isometric contraction (MVIC) in order to measure peak torque (PT_MVIC) and a 1-second MVIC to measure the rate of torque development (RTD) over a time gap of 0–200 milliseconds. The mean average value of these three measurements (i.e., PT_MVIC and RTD) was used for further analysis. Contractile properties were also analyzed as they are significant markers of the mechanisms underlying force generation in muscles. Lastly, muscle activity was assessed by electromyography (EMG-RMS).

The findings of the study revealed that both whole-body and thigh PhAs are associated with the muscle strength of knee extensors (with thigh PhA being the preferred predictor of knee extensor strength). However, this association was understood to be due to the muscles’ contractile properties rather than any neural aspects. Thus, both measurements could not predict neuromuscular activity or the explosive muscle strength (which largely depends on neuromuscular control) of knee extensors.

This study holds much promise for present and future implications. Speaking about the present, being able to assess knee muscle strength is very important, especially for the elderly (in whom strong knee muscles mean greater independence to move about), and athletes (who need to maintain knee muscle strength in order to perform better). The above findings show a new avenue of assessing muscle strength for not only healthy adults, but also those suffering from orthopedic or cognitive disorders. And speaking of the future, Dr. Akagi tells us the implications of their work: “People can assess their muscular condition by BIA in just a few seconds. Moving forward, we may be able to build a system that uses a person’s BIA to provide them with advice to promote their health.”

The research team may just be looking at the future of health technology!

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Reference

DOI: https://doi.org/10.3389/fphys.2022.965827

About Shibaura Institute of Technology (SIT), Japan
Shibaura Institute of Technology (SIT) is a private university with campuses in Tokyo and Saitama. Since the establishment of its predecessor, Tokyo Higher School of Industry and Commerce, in 1927, it has maintained “learning through practice” as its philosophy in the education of engineers. SIT was the only private science and engineering university selected for the Top Global University Project sponsored by the Ministry of Education, Culture, Sports, Science and Technology and will receive support from the ministry for 10 years starting from the 2014 academic year. Its motto, “Nurturing engineers who learn from society and contribute to society,” reflects its mission of fostering scientists and engineers who can contribute to the sustainable growth of the world by exposing their over 8,000 students to culturally diverse environments, where they learn to cope, collaborate, and relate with fellow students from around the world.

Website: https://www.shibaura-it.ac.jp/en/

About Professor Ryota Akagi from SIT, Japan
Ryota Akagi presently serves as a Professor for the Department of Life Sciences at the Faculty of Systems Science and Engineering, Shibaura Institute of Technology (SIT) in Saitama, Japan. Dr. Akagi has held other notable positions over the course of his career from holding a visiting researcher position at RIKEN, Japan to serving as a visiting Associate professor for the University of Guelph, Canada. He holds a PhD in Sports Science from Waseda University, Japan, and has over 78 publications to his credit. His research focus primarily involves muscle mechanics, exercise physiology, resistance training, biomechanics and sport sciences.

Funding Information
This study was supported by JSPS KAKENHI Grant number JP17KK0174 (to RA).