Chemotherapy treatment changes muscle activation, but not the perception of effort on women with breast cancer

Resumo

Objective: The objective of this study was to analyze the effects of chemotherapy cycles on muscle activation (MA) and
rated perceived exertion (RPE) in women with breast cancer. Methodology: A total of 21 women were divided into a treatment group (TG) (47.2±11.3 years old) and a control group (CG) of women without cancer (53.7±6.3 years old). The women in
the TG had been diagnosed with breast cancer and were undergoing chemotherapy (anthracyclines®). MA analyses were
performed and RPE between the second and third cycles of chemotherapy (baseline) and post-treatment (fourth cycle).
The miotec® 200 model electromyograph was used to evaluate the MA, and the root-mean-square values of the rectus
femoris and vastus medialis muscles were analyzed during the sit-to-stand test, as well as the RPE at the end of the test
(Borg scale). Date is presented as mean and standard deviation. The two-way ANOVA test was used to compare the means
between the moments and groups using the post-hoc Bonferroni. The significance level was defined at p<0.05. Results: The
TG and CG differed at baseline in the MA of the vastus medialis (188.2±125.3 and 313.6±142.7, respectively; p=0.02) and
rectus femoris (138.3±63.1 and 298.5±176.9, respectively; p=0.01). Just like in the post-treatment MA of the vastus medialis
(172.7±121.2 and 352.3±198.3, respectively; p=0.01) and rectus femoris (150.5±66.8 and 406.6±282.1, respectively; p=0.00).
However, no significant changes were found in the RPE between TG and CG in the baseline (10±2.7 and 11±2.8, respectively; p=0.33) and post-treatment (11.8±3.3 and 11.7±3.1, respectively; p=0.98). Conclusion: Chemotherapy seems to significantly change MA, but not RPE in women with breast cancer when compared with healthy women.