# Effects of a Short-Term Supervised Exercise Program in Women with Breast Cancer
## 4 Discussion
A combined strength and endurance program yields better results in aerobic endurance capacity, patient-reported physical functioning, bodily pain, fatigue, and endocrine symptoms compared to a standard aerobic exercise dose (25-30 min) [60]. Furthermore, in other programs where aerobic exercises were implemented for 12 to 16 weeks [24; 40], although they were safe and tolerable, only modest improvements were achieved in cardiorespiratory fitness in early-treated breast cancer patients [24], or improvements in cardiorespiratory fitness without any conclusive evidence on the effect of cardiotoxicity in HER2-positive breast cancer patients treated with adjuvant therapy with trastuzumab [40]. Another factor that may have contributed to improvements in muscle strength was the intensity of the prescribed exercise. Participants were encouraged to control intensity, aiming for an RPE between 7 and 8 (very hard) out of 10 in the final repetitions of each strength exercise. This is because the American College of Sports Medicine, in the ACSM Guidelines for Exercise and Cancer [61], considers work performed at this threshold as vigorous physical activity, recommending 2 to 3 days of exercise per week at this intensity, performing two sets of eight to 12 repetitions each. Regarding the intensity of cardiorespiratory exercise, it was rated between 4 and 6 out of 10 (considered moderate), consistent with the intensity recommended by the ACSM for this type of patient. In other studies where RPE was used to control intensity (both in strength and aerobic exercise), the intensity started at a moderate level in the first month and gradually increased over the weeks, reaching a level between hard and very hard in the third month [25]. In our study, we chose to prescribe high intensity from the beginning of the program to achieve adaptations in a shorter period. The inclusion of stretching exercises in almost one-third of the daily session was due to several reasons: (1) the positive effect of stretching on adaptations of endothelial function and muscle blood flow in elderly rats, increasing microvascular volume, the number of capillaries per muscle fiber, levels of hypoxia-induced factor-1\(\alpha\), vascular endothelial growth factor, and endothelial nitric oxide synthase [62], (2) increased shoulder range of motion and a decrease in chest tightness and pain after breast cancer surgery [63; 64], (3) reduction in tumor growth due to restoration of cytotoxic immunity by reversing the impairment of cytotoxic CD8+ T lymphocytes and activation of T cells, which play a central role in immune defense [65], (4) furthermore, resolvin D1 (RvD1) and resolvin D2 (RvD2), pro-resolving lipid mediators (SPM) with anti-inflammatory properties [66; 67], were significantly higher in stretched mice compared to control mice [65; 66], reducing acute inflammation. Therefore, improvements in quality of life and reduction in fatigue could be attributed to the performance of exercises. Finally, we would like to point out that based on the available evidence, it is likely that the supervision and intensity of the sessions, rather than the duration of an exercise program, justify the improvements observed in this type of patient. Therefore, we find improvements related to the quality of life [24; 25; 35; 50; 68], fatigue [23; 24; 45], or functional capacity [25; 59] in interventions that are fully supervised with an average duration of 12 to 24 weeks. However, these improvements are not observed in other longer programs(18 to 52 weeks) characterized by less rigorous supervision [69], telephone supervision [70], or evolution from supervision to autonomous work, either progressively [42] or immediately [41]. Therefore, we believe that a shorter duration program that is rigorously supervised will be effective in improving the quality of life of cancer patients, thus allowing the optimization of human and material resources available to adequately respond to the constant increase in the incidence of these types of pathologies.