New research shows a better way to easily assess knee muscle function

A simple and popular alternative is the use of bioelectrical 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) can be measured. membrane). Phase angle (PhA), a measurement derived via BIA, is calculated using the resistance and reactance of the tissue. It is directly proportional to muscle cell mass and function. Many studies have linked PhA across the body to maximal muscle strength, but none associate PhA with knee extension strength or explosive muscle strength (the force required to make fast, powerful movements such as sprinting or standing up from a chair) in adults. Taking into account the importance of knee muscle strength – especially in the elderly, who need it for their independence, and athletes, who need strong knees for better performance – such a study was necessary.

In this spirit, 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 Sports Sciences, Waseda University; and researchers Yosuke Yamada and Tsukasa Yoshida from the Healthy Longevity Research Section, National Institute of Health and Nutrition, National Institutes of Biomedical Innovation, Health and Nutrition examined the association of PhA with the neuromuscular properties of knee extensor muscles in both young and older people. adults. Their findings were published in Part 13 of Frontiers in physiology on August 11, 2022. Dr. Akagi and Dr. Hirata, the corresponding authors of the paper, tell us: “We wanted to assess the association of PhA in the thigh with maximal muscle strength, explosive muscle strength, contractile properties and neuromuscular activity. and find out which of the two – whole body PhA or the thigh – was a better predictor of knee extensor strength.

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

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

This study is promising for current and future implications. Speaking of the present, being able to assess knee muscle strength is very important, especially for the elderly (where strong knee muscles mean greater independence in movement) and athletes (who need to maintain knee muscle strength to perform better ). . The above findings demonstrate a new way to assess muscle strength not only for healthy adults, but also for people suffering from orthopedic or cognitive disorders. And speaking about the future, Dr. Akagi shows us the implications of their work: “People can assess their muscle condition in just a few seconds using BIA. In the future, we may be able to build a system that uses a person’s BIA to provide them with advice to promote their health.”