Long-Term Side Effects of Breast Cancer on Force Production Parameters

ABSTRACTBertoli, J, de Souza Bezerra, E, Dias Reis, A, Amice da Costa Barros, E, Gobbo, LA, and Forte Freitas Júnior, I. Long-term side effects of breast cancer on force production parameters. J Strength Cond Res XX(X)000–000, 2020—Breast cancer treatments have long-term side effects, which are associated with muscle strength reduction, negatively affecting the quality of life and increasing the chances of a sedentary life style. The aim of this study was to analyze the effects of types of surgery and hormone therapy on muscle strength parameters in breast cancer survivors compared to women without cancer (control). Eighty-three women, 42 breast cancer survivors and 41 control women, volunteered to participate in this study. Subjects performed maximal isometric voluntary contractions, so that force parameters of the right and left shoulder abductor, trunk extensor, and preferred knee extensor-flexor muscles could be evaluated. Overall, breast cancer survivors presented a lower absolute and normalized maximal force (Fmax) for all muscle groups compared with control. The right shoulder abductor muscles of breast cancer survivors presented a significantly lower absolute and normalized rapid force index (RFI) than control. When compared according to hormone therapy treatment, in breast cancer survivors undergoing aromatase inhibitor, all strength parameters except for normalized RFI demonstrated lower values for the right and left shoulder abductors, trunk, and knee extensors compared with control and tamoxifen. When separated by surgery type, breast cancer survivors who underwent quadrantectomy and radical mastectomy presented lower values for some strength parameters for the left and right shoulder abductors, except for trunk extensor muscles, in which quadrantectomy and total mastectomy presented lower strength parameters. It is recommended that breast cancer survivors should be encouraged to perform supervised strength training programs for different muscle groups to improve Fmax and RFI, aiming to reduce muscle weakness and pain, and improve functional capacity and quality of life.