Study shows a new way to assess muscle strength

Study shows a new way to assess muscle strength

Muscle strength and its improvement are important for everyone in everyday life. Traditionally, muscle function can be assessed through physical performance tests and/or muscle strength measurements. However, these methods are not applicable to people who cannot perform forceful muscle contractions, such as infants, the elderly, and patients with injuries or cognitive disorders (such as dementia).

A simple and popular alternative is bioelectrical impedance analysis (BIA), which can quickly and non-invasively measure tissue resistance (which depends on the amount of water and electrolytes in the tissue) and reactance (which depends on the integrity of the cell membrane). Phase angle (PhA), a measurement derived via BIA, is calculated based on the resistance and reactance of the tissue. It is directly proportional to muscle cell mass and function. Many studies have linked whole-body PhA to maximal muscle strength, but there are none that link PhA to knee extensor strength or explosive muscle strength (which is the strength required to perform fast, strong movements such as sprinting or standing up from a chair) in adults. Given the importance of knee muscle strength - particularly in older people, where it is necessary for independence, and in 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 Science, Waseda University; and researchers Yosuke Yamada and Tsukasa Yoshida from the Division of Healthy Longevity Research of the National Institute of Health and Nutrition and the National Institutes of Biomedical Innovation, Health and Nutrition examined the association of PhA with the neuromuscular properties of the knee extensors in both young and older adults. Their findings were published in Volume 13 of Frontiers in Physiology on August 11, 2022. Dr. Akagi and Dr. Hirata, the corresponding authors of the article, tell us: "We wanted to assess the relationship between thigh PhA and 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 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 (PTMVIC) and a 1-second MVIC to measure rate of torque development (RTD) over a period of 0–200 milliseconds. The mean average value of these three measurements (i.e., PTMVIC and RTD) was used for further analysis. Contractile properties were also analyzed as they are important indicators of the mechanisms underlying force generation in muscles. Finally, muscle activity was assessed using electromyography (EMG-RMS).

The results of the study showed that both whole-body and thigh PhAs were 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 rather than neural aspects. Therefore, both measurements failed to predict either neuromuscular activity or explosive muscle strength (which largely depends on neuromuscular control) of the knee extensors.

This study holds promise for current and future implications. At present, it is very important to be able to assess the strength of the knee muscles, especially for older people (for whom strong knee muscles mean greater freedom of movement) and for athletes (who need to maintain the strength of their knee muscles in order to perform better). . The above results demonstrate a new way to assess muscle strength not only in healthy adults, but also in people with orthopedic or cognitive disorders. And when we talk about the future, Dr. Akagi the impact of her work: "People can assess their muscle condition based on BIA in just a few seconds. In the future, we may be able to build a system that uses a person's BIA to deliver." them with advice on how to promote their health.”

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

Source:

Shibaura Institute of Technology

Reference:

Hirata, K., et al. (2022) Can the phase angle from bioelectrical impedance analysis be related to the neuromuscular properties of the knee extensors? Limits in physiology. doi.org/10.3389/fphys.2022.965827.

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