Eccentric Calf Training Alters Segmental Bioelectrical Parameters Indicative Of Muscle Damage

Segmental bioelectrical impedance analysis (BIA) assesses cellular health through phase angle (PhA), resistance (R), and reactance (Xc), which may offer insight into localized muscle and fluid balance changes during recovery from exercise. PURPOSE: The aim of the study was to evaluate segmental BIA parameters after eccentric calf training sessions. METHODS: Twenty male participants (82.6 ± 16 kg; 177 ± 8.7 cm; 23.8 ± 3.45 yrs) performed a unilateral eccentric plantar flexor training session comprising four sets of 50 repetitions, separated by 60 seconds of rest, while wearing a weighted vest (40% of body mass), followed by a fifth set to the point of failure. One leg was randomly assigned to the intervention (eccentric training), while the other served as a control. Along with a series of strength measures, the following BIA parameters were evaluated in each leg before the training session (pre), immediately post-exercise, and 24-, 48-, and 72-hours post-training: intracellular water (ICW) and extracellular water (ECW), as well as R, Xc, and PhA at 50 kHz. A two-way (leg×time) repeated measures ANOVA was used to evaluate each of the BIA parameters. RESULTS: Significant leg×time interactions were found for all BIA parameters (p < 0.050). Compared to pre-, ECW (p < 0.001; ↓0.250 ± 0.021 L), Xc (p < 0.001; ↑3.035 ± 0.387 Ω) and R (p < 0.001; ↑13.873 ± 1.69 Ω) were significantly different in the intervention leg immediately post-exercise, while the PhA was different immediately after (p < 0.001; ↑0.31 ± 0.04°), 24-hours (p < 0.001; ↓0.31 ± 0.04°) and 48-hours post-exercise (p = 0.022; ↑0.22 ± 0.07°). The ICW in the intervention leg was the only BIA parameter to show significant differences from pre- at all time points (p < 0.050; range: ↓0.267 to ↓0.169 L). The control leg showed significant differences from pre- to immediately post-exercise for ICW (p = 0.001; ↓0.133 ± 0.021 L), ECW (p = 0.001; ↓0.121 ± 0.020 L), Xc (p = 0.002; ↑1.385 ± 0.302 Ω), R (p = 0.001; ↑6.966 ± 1.33 Ω) and PhA (p = 0.048; ↑0.11 ± 0.03°) which may have occurred acutely due to the strength testing. CONCLUSION: Segmental BIA parameters exhibited significant post-exercise changes in muscles subjected to eccentric training, with varied time courses that may be indicative of the primary and secondary phases of muscle damage.