Table 1 shows that in the first study we used an exercise protocol that made use of high loads between 75% and 85% of one repetition maximum (1 RM) versus low load exercises between 55% and 65% of 1 RM, for women survivors of Breast cancer (BC) with clinical diagnosis of Secondary lymphedema. We know that women who have undergone a surgical intervention due to BC, tend to report the increase of symptoms including pain, heaviness, numbness and stiffness in the upper limb.
In addition, there is a considerable loss of muscle strength in the affected arm[17,18]. And with the loss of strength come the limitations of biomechanical functions[19,20]. The physical exercise in particular the training with external loads, is one of the most used strategies for the improvement of the biomechanical function through the increase or restructuring of the muscular strength[20,21].
The treatment through training with external loads also contributes to the increase of lymphatic clearance through the natural effect of[22,23] muscle pump. It is observed that the exercise performed with the lifting of higher loads between 70% and 95% of 1RM, bring additional advantages in relation to the percentages of lower loads, the literature states that there is a relationship between the load response of the exercise of Strength and magnitude of gains in muscle structure and function[24,25].
The results of the first study in table 1 corroborated the physical evolution of CM survivors, considering that the group that performed the intervention between 75% and 85% of 1 RM, also presented higher gains in relation to the increase in the functionality of the force and muscular resistance when compared to the control group. It is noteworthy that the same occurred with the group that performed the interventions between 55% and 65% of 1 RM and that no differences were found between the groups, in relation to the level of the swelling of the lymphedema and the other symptoms. In addition, a significant improvement in quality of life (QOL) was identified in the women studied.
Therefore, the results indicate that women surviving BC, (provided they are accompanied by a qualified and appropriate professional to perform interventions with physical exercises), even if they are lymphedema secondary to BC, can make the use Low loads, and high in interventions for physical improvement and QOL. It is known that exercise is a beneficial and positive therapy for this population, whether it is applied during and or after the course of the disease, resulting in expressive clinically proven improvements, regardless of the intensity or type of exercise used in Intervention[26,27].
Another reason to use the practice of exercises in treatment procedures or oncologic prevention is that cancer cells feed on energy reserves, which are stored in the human body in the form of adipose tissue. For this reason the adipose body mass potentializes the risks for the acquisition of various types of cancer, making it necessary to include regular physical exercise during the treatment process with the objective of decreasing and/or preventing the increase in the levels of Adiposity.
One of the training methods, which has been highlighted is the high intensity interval training known as HIIT (High intensity Interval Training), which in addition to showing good results in relation to its efficiency for body slimming, has become another tool to be used in the treatment of surviving women of BC.
In the results of the second article also contained in table 1, we observe the use of a multimodal rehabilitation protocol, which made use of HIIT with intensity at 95% of the peak of the maximal heart rate and compared with the exercises of low to moderate intensity.
The group that performed the intervention with HIIT obtained body fat reduction, while in the low to moderate intensity group there were no changes in relation to this variable. Similar results are found in the study by Devin, who underwent intervention of four weeks of high intensity exercise and identified improvements in both cardiorespiratory fitness and body composition of the studied sample, which was Comprised of women surviving cancer.
Nowadays, it is evident in the literature that the use of high-intensity exercises is safe and effective in this population 15. The results of this study strengthen this fact, considering that the HIIT protocol brought positive data for quality of life, reduction of body fat and fatigue. Reinforcing this way, the exercise protocol of low to moderate intensity also promoted benefits for the group that performed it. Thus, HIIT can be used in women survivors of BC without risks to the quality of health, bringing the advantage of having a shorter chronological time of implementation of the Protocol when compared to the method of exercises of low to moderate intensity.
It is important to emphasize that women who experience the treatment of breast cancer present a great decline in QOL, especially in aspects that involve social and emotional life, which ends up affecting their functions of autonomy and biomechanics. Thus, general health impairment is observed, reducing the cardiorespiratory, metabolic, fitness and increase of body fat, being these risk factors predictors of the disease and quite detrimental to the success of the treatment[27,28].
Being physically active, it brings several contributions to the QOL and acts in parallel in the prevention of various types of diseases. Moreover, they have a positive influence on mood, improves body image and self-esteem, acting in this way in the reduction of the sequels and the physical and emotional symptoms experienced during the treatment of Cancer.
Figure 4 (Forest Plot of quality of life components: physical function; emotional function; and social function.), exposes the results of the QOL variables, that were analyzed in common by both of the studies used in this systematic review, and as we observe the meta-analysis it is observable that there was no statistical difference in relation to which type of intervention influence more in the improvement of physical functions, Emotional and social that make up the QOL. Thus, considering QOL, it is suggested that women who have undergone a process of breast cancer treatment may have improvements in the functions previously cited independently of the intensity and exercise protocol. Regarding the heterogeneity of the variables, it can be verified that the component emotional function presented 75% difference between the studies the reason for justifying this evidence can be explored through the use of distinct instruments in each study for the analysis of the emotional function component; By the difference in the number of participants in each sample due to the physical and emotional, psychological and biological individuality of the women studied and the different types of protocols used in physical exercise interventions.
On the reliability of the studies used in this study, figure 2 (risks of biases of the studies used.), the data showing the final evaluation of the vises of the articles used in this research are contained, and both showed low credibility only In the “blinting” process by the samples used. These studies did not report whether there was such a procedure during the surveys, which clearly leaves the possible performance bias during the data collection phase. When analyzing each article in isolation as shown in figure 2, it is perceived that in the content of author J. Schmitt et al., (2016), there is partially the selection and detection bias, while the work of P. Come et al., (2013), showed to be safer in these criteria more confidence for possible readers to reproduce the procedures described in their research.
Given the facts, it is worth highlighting that the bibliographic productions up to the present day in relation to the theme in question are scarce and the studies evaluating the relationship of physical exercise with treatment during or after cancer, have stated that interventions with the Physical exercise are beneficial, but the data of the publications are inconsistent with respect to volume or intensity, pillars of training prescription, to be recommended during interventions[33,34]. And for safety precautions The scholars of the oncology area, encourage the use of simple exercises that simulate the activities of daily life, and that have mild and moderate intensities in order to avoid complications in the biomechanical health[13,14–35].
Despite this systematic review with meta-analysis eviding the effects of high-load exercise and high intensity on body health and quality of life during the treatment of breast cancer survivors (BCS), caution is suggested regarding their prescription, Current literature is still limited on the subject and because of this, there is still no favorable consensus regarding the prescription of intense exercise for BCS. It is necessary to further research to broaden the understanding of the effect of the practice of these exercises in BCS.