Author(s): STAVINSKI, N., MAGALHÃES, J., ROSA, G., SARDINHA, L., CYRINO, E., Institution: STATE UNIVERSITY OF LONDRINA, Country: BRAZIL, Abstract-ID: 2526

INTRODUCTION:
Bioelectrical impedance analysis (BIA) parameters are often associated with cellular health and plausibly with muscle function. On the other hand, it is unknown whether prospective changes in muscle thickness due to resistance training (RT) are associated with changes in BIA-derived parameters. Therefore, we aimed to analyze the synergistic relationship between changes in muscle mass and BIA-derived parameters following 12 weeks of RT in older women.
METHODS:
One hundred and seventeen older women (69.4 yrs ± 5.7 yrs) were allocated either to a RT group (n = 56) to be submitted to a 12-week RT full-body program or to a control group (n = 61). Both groups were evaluated at the beginning of the study and after 12 weeks using a BIA device to assess reactance (Xc, ohms), resistance (R, ohms), and phase angle (PhA, º), while a B-mode ultrasound was used to determine muscle thickness of three sites (arm flexors, and lateral and mid-thigh). The sum of the three sites was used as a surrogate for muscle thickness measurements (SUMmt). Dual-energy X-ray absorptiometry was also used to estimate total fat mass (FM). Repeated measures correlation was used to examine the synergistic relationship between BIA parameters and muscle thickness over time, while linear mixed models with a random intercept were used to determine the relationship when adjusted for age and FM.
RESULTS:
After the intervention, Xc significantly increased in RT group (48.3 ± 7.8 to 52.8 ± 7.4) and reduced in control group (49.4± 8.22 to 46.7± 8.20), with a significant group*time interaction at the follow-up (P < 0.001). R increased only in RT group (555 ± 68 to 571 ± 63), while PhA increased in the RT group (4.97 ± 0.52 to 5.28± 0.50) and reduced in the control group (5.03 ± 0.48 to 4.78 ± 0.52), with a significant group*time interaction at the follow-up (P < 0.001). The SUMmt (cm) increased in RT group (18.2 ± 3.1 to 19.4 ± 3.0) and reduced in the control group (18.5 ± 2.8 to 17.9 ± 2.7), with a significant group*time interaction at the follow-up (P < 0.001). The SUMmt was associated with Xc (rrm = 0.50), R (rrm = 0.42), and PhA (rrm = 0.44) in the RT group, whereas no significant association was found between SUMmt and the BIA parameters in the control group (P ≥ 0.050). When adjusted by age and FM, a one-unit increase in the SUMmt in the RT group was associated with an increase of 0.83 ohms (CI 95%: 0.13/1.55 ohms) in Xc and 0.11º (CI 95%: 0.07/ 0.15º) in PhA, but not associated with R (P = 0.625). On the other hand, a one-unit increase in the SUMmt in the control group was associated with a reduction of -7.50 ohms (CI 95%: -12.6/-2.4 ohms) in R and 0.07º (CI 95%: 0.02/0.12º) in PhA, but it was not associated with Xc (P = 0.922).
CONCLUSION:
Changes in SUMmt induced by RT can explain a significant part of the BIA parameters in older women. Our results suggest that changes in muscle thickness due to RT might have a role in cellular health.