Bioelectrical Impedance and Muscle Thickness during Resistance Exercise of Upper Arm

Muscle tissue swelling occurs immediately after exercise. Conventionally, this phenomenon has been evaluated by diagnostic imaging methods such as ultrasonic B-mode imaging. On the other hand, bioelectrical impedance analysis (BIA) is a simpler method to measure this phenomenon. In the BIA, changes in water volume inside and outside ofmuscle cells during exercise can be evaluated as changes in bioelectrical impedance (BI). In this study, the local muscle fatigue was effectively measured using BIA by concentrating the current in a narrow area and the results were compared with muscle thickness measured by ultrasonic B-mode imaging. The measurement site was the upper arm, and the exercise condition was four sets of arm curl exercise. Measurements ofupper arms were taken before exercise (base line: BL) and after each exercise set (post exercise: PE1-4). BI was converted into external cell water resistance (RECW), internal cell water resistance (RICW), and their parallel resistance (RICW//RECW). The results showed that RECW increased before PE1 and decreased after PE1. Therefore, exercise hyperemia was inferred to be a factor in muscle swelling after PE1. Then, the correlations between RECW, RICW, RICW//RECW and muscle thickness were calculated. Subsequently, a significant correlation was obtained between RICW//RECW and muscle thickness, especially after PE1. © 2024, Japan Soc. of Med. Electronics and Biol. Engineering. All rights reserved.