Researchers from SIT report that thigh phase angle measurements—derived from BIA—can be used to predict knee extensor strength in adults. Image courtesy of Prof. Ryota Akagi from SIT.
Scientists from Shibaura Institute of Technology (SIT), Japan, have investigated the usefulness of bioelectrical impedance analysis (BIA) in assessing muscle function and parameters, 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 in adults.
The findings, which show a new avenue of assessing muscle strength, 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.
Present implications of this work include 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. Future implications include building a system that uses a person’s BIA to provide them with advice to promote their health.
