Postmenopausal breast cancer survivors undergoing tamoxifen treatment, who will do the evaluations before the beginning and after 12 weeks of exercise training and subsequently 12 weeks of detraining.

The exercise training program will last 12 weeks, with a frequency of three sessions per week, held on Mondays, Wednesdays, and Fridays. Each session will last approximately 50 minutes. Whenever the maximum number of pre-established repetitions is successfully performed, the intensity will be increased by 5 to 10%. All sessions will be supervised by trained professionals.

Blood samples will be collected after 8-10 hours overnight fasting directly in evacuated tubes containing separator gel. After centrifugation for 10 min at 3000 rpm, the serum will be separated for immediate analysis or stored at -80 °C for further analysis. Serum levels of IL-4, IL-6, IFN-γ, TNF-α and Adiponectin will be determined by enzyme-linked immunosorbent assays (ELISA) using commercial kits (BD Biosciences, San Jose, CA, USA), according to the manufacturer's instructions, in an Immulite 2000 analyzer (BD Biosciences, San Jose, CA, USA). Expressed in pg/mL.

Blood samples will be collected after 8-10 hours overnight fasting in evacuated tubes containing separator gel. After 10 min centrifugation at 3000 rpm, the serum will be stored at -80 °C for further analysis. Lipid peroxidation was estimated by determining the serum concentration of thiobarbituric acid reactive substances (TBARS). The TBARS concentration will be obtained by spectrophotometric reading at 535 nm and interpolation in a malondialdehyde calibration curve. Oxidative damage to serum proteins will be estimated by determining the concentration of carbonylated proteins by reading the absorbance at 370 nm and using the molar absorptivity coefficient of 22.000 M-1cm-1. The levels of non-protein thiols will be obtained by the colorimetric method based on the reaction of the sulfhydryl group with 5,5'-dithiobis (2-nitrobenzoic acid) (DTNB). Expressed in mmol/L.

Blood samples will be collected after 8-10 hours overnight fasting directly in evacuated tubes containing separator gel. After centrifugation for 10 min at 3000 rpm, the serum will be separated for immediate analysis or stored at -80 °C for further analysis.Catalase (Cat) activity was evaluated by the ability of this enzyme to convert H2O2 into O2 and H2O. Expressed in K/gHb.s.

The test of one-repetition maximum (1-RM) was adopted to assess muscle strength in all exercises, except for abdominal exercise on the ground, which will be performed only with body mass. Before each test, the subjects will perform a general warm-up (3-5 minutes of light activity), followed by dynamic stretches also for the muscles involved. Then, the participants will perform a specific set of warm-ups that consisted of 8 repetitions with approximately 50% of the estimated load for 1-RM, followed by 3 repetitions with 70% of the estimated load for 1-RM. Subsequently, the loads will be progressively increased until the 1-RM load was found. Rest intervals of approximately 4 to 5 minutes will be inserted between each attempt and the result will be considered valid when performed properly, in a controlled manner, and without assistance from the researchers involved in the assessment. The number of attempts to determine such values will be not more than five. Expressed in kg.