Bioimpedance analysis for identifying new indicators of exercise-induced muscle damage

Abstract

A noninvasive, immediate, and convenient method for assessing muscle tissue status during exercise-induced muscle damage (EIMD) has not been established. This study was designed to assess and determine parameters suitable for measuring EIMD after eccentric exercise, using multi-frequency bioimpedance analysis (BIA). Thirty-five young male participants performed dumbbell exercises with their left arm, and their BIA parameters were measured at various time points up to 168 h post exercise using a multi-frequency BIA device. At all-time points, intra and extracellular water content was greater in the left arm than in the right arm, whereas the impedance, reactance, resistance, and phase angle were lower in the left arm than in the right arm. Established EIMD indices, such as maximal isometric voluntary contraction, were measured and used in correlational analyses. Only reactance was correlated with biomarkers, indicating muscle damage (r = - 0.56 to - 0.49). Furthermore, reactance was found to correlate well with indirect indicators of EIMD, suggesting that it may be a suitable marker for evaluating EIMD. However, the relationship with the limited evaluation indices employed in this study is constrained. Future studies should investigate the correlation between reactance and direct damage indicators, such as structural damage, observed in biopsies.

Keywords: Bioimpedance analysis; Biomarker; Correlation analysis; Eccentric exercise; Exercise-induced muscle damage; Reactance.

Figure 1

Time course of EIMD evaluating indices. (a) Range of motion, (b) maximum voluntary contraction, (c) soreness during elbow extension, (d) circumference of the upper arm, e: urinary titin N-terminal fragment, ^†p < 0.05, ^††p < 0.01, ^†††p < 0.001.

Figure 2

Time course TBW, ECW, and ICW. (a) Total body water; (b) extracellular water; (c) intracellular water; *p < 0.05, **p < 0.01, ***p < 0.001.

Figure 3

Time course of each bioimpedance analysis parameter. (a) 5 kHz phase angle, (b) 50 kHz phase angle, (c) 250 kHz phase angle, (d) 5 kHz impedance, (e) 50 kHz impedance, (f) 250 kHz impedance, (g) 5 kHz reactance, (h) 50 kHz reactance, (i) 250 kHz reactance, (j) 5 kHz resistance, (k) 50 kHz resistance, (l) 250 kHz resistance, * p < 0.05, ** p < 0.01, *** p < 0.001.

Figure 4

Ratio of extra- and intracellular water to total body water. TBW total body water, ECW extracellular water, ICW intracellular water, *p < 0.05, ** p < 0.01, *** p < 0.001.

Figure 5

Relationship between the electrical characteristic parameters and EIMD evaluation indices. Areas with higher levels of correlation coefficient are depicted as darker, and those with lower levels of correlation coefficient as lighter. Areas with no statistically significant differences are not colored. ROM range of motion, MVC maximum voluntary contraction, SOR muscle soreness, CIR upper arm circumference, UTF urinary titin N-terminal fragment. *p < 0.05, **p < 0.01.