DISCUSSION
muscle relaxation, CBKF, precariousness
SAID, MUSCLE RELAXATION
The sample was homogeneous and composed of young adults, mostly female. The Nursing Profile in Brazil survey showed that there has been a rejuvenation of nursing staff, with 49.6% in the range of 31 to 45 years and 85.1% female, a phenomenon that has occurred for many decadesThis study identified a high number of professionals working overtime in an institution that uses overtime, which characterizes a strategy for supplementing the income of these workers. Nursing professionals’ low remuneration has been a subject discussed for years as well as the hegemony of other categories that work with shorter hours and higher wages. Excessive hours or double shifts as well as precariousness of nursing work can lead to occupational illnessAs for the instruments, in OSL and WRSS, it was found that CBKF did not have a statistically significant effect. This result demonstrates that there was no change in nursing professionals’ perception about the stress symptoms and occupational stress. The issue of the possibility of perpetuation of organizational factors and work-related stressors throughout the tested intervention is considered, which made it impossible for workers to perceive improvement. Also, intervention time may have been insufficient to obtain a response perception in the IG.The OSL score that suffered the greatest decrease was in the CG, demonstrating that this mean reduction was not related to the intervention. This group may have been more sensitive to a placebo effect, as participants were blinded. A similar result occurred in a study that assessed the effect of massage and aromatherapy for stress reductionOn the other hand, this randomized clinical trial (RCT) aimed to assess whether using an activity with monitoring would produce a different result in terms of stress when compared to another without monitoring, which did not occur. Currently, it is known that using games, such as puzzles, can bring numerous benefits to users. A study developed with chronically stressed patients demonstrated that using games generates fun, engagement and mentally removes the sources of stressAnother clinical trial was carried out with nurses from inpatient units at the Massachusetts Hospital, which tested a program with breathing exercises for two weeks, finding no effect on stress. The authors did not raise a hypothesis for this finding, but they relate the result to the fact that nursing prioritizes care for the other to the detriment of their own, a fact that needs to be worked on in teams by organizationsIt should be noted that this RCT was carried out during the pandemic period and that all professionals surveyed were in similar work scenarios. Moreover, other stress-generating sources occurred during collection, which are part of the institution organization, such as election for change of direction, service and unit heads as well as organizational changes for patient safety purposes and preparation for the international accreditation process.Although there were no changes in the scales, a series of HRV indicators underwent changes throughout the research. This fact demonstrates that, even if workers did not perceive the reduction of stress symptoms or occupational stress, they were somehow present.All HRV indicators showed a time effect, demonstrating that one or both groups changed over the sessions (p<0.050). With the exception of HF-LF ratio and cardiac coherence, the CG showed similar behavior to the IG in the other indicators, with an increase in the means in SDNN and rMSSD. This result may indicate that moving away from the work routine and concentrating on another activity, even a simple one, such as a puzzle, and for a short period (approximately 10 minutes), may bring about changes in biomarkers over time and, consequently, health benefits.Another factor to be considered is that the professionals felt “taken care of” by someone in a moment of overload. The placebo effect involves cognitive and emotional factors, in addition to genetics and learning mechanisms, and can be added to active treatment and optimize the expected results when individuals believe that a treatment will help themSDNN showed a group effect, in addition to time effect, demonstrating a difference between those who received the intervention and those who did not. The significant increase in the means of IG sessions, when compared to the means of the CG, demonstrated the effect of HRV CBKF on this indicator, which represents a summary of all HRV indicators, being considered an indicator of globality.On the other hand, the interaction between sessions versus group did not show a significant result in IG and CG in relation to SDNN, demonstrating that the intervention time was not responsible for the increase in the means found, data that corroborates the investigation that showed a positive result in only one CBKF sessionIncreased SDNN means greater HRV, characterizing better autonomic regulation through the parasympathetic nervous system’s (PNS) prompt action when there is sympathetic activation, good physiological adaptation and, consequently, positive response in the presence of stressful situationsThe rMSSD showed only a time effect, with an increase in means in both groups, predominantly in the CG. This indicator represents an increase in vagus activity over the heart, which can be understood as a parasympathetic response to activities performed. Increased parasympathetic activity is related to times of relaxation, rest, rest, and therefore, a reduced stress response. In this sense, it can be said that, based on the result found in the CG, the puzzle activity triggered greater relaxation than CBKF. For some authors, the increase in rMSSD means adjustments in the coping response and better response to moments of adversityThe LF/HF ratio showed a statistically significant difference in the three GEE effect models, demonstrating that the intervention produced autonomic balance in the IG, indicating a balance between SNS and PNS, while the same did not occur in the CG. The effect of the group versus time interaction reinforces that, over time, there was a statistically significant difference in the LF/HF ratio in the comparison between those who used HRV CBKF and those who received the placebo activity. A study that compared the effect of HRV CBKF with muscle relaxation in university students identified a similar result in the LH/HF ratio, with an increase in the means in BKF HRV and maintenance of values in the muscle relaxation groupUsing HRV CBKF protocols has shown effectiveness in different populations and, for this reason, has been used in stress management programs. Using a well-defined protocol, with slow and deep breathing training (cycles around 6 breaths per minute), increases HRV and tends to significantly increase SDNN and LF, a result found in this studyHeart coherence means showed a statistically significant difference in the three GEE models, demonstrating that HRV CBKF had an effect on this indicator. Furthermore, an increase in the mean was observed in the IG from the second session, and the same was maintained throughout the entire intervention protocol. HRV CBKF training aims to regulate physiological parameters to achieve cardiac coherence. Frequent training with well-defined protocols favors the maintenance of a state of coherence and, consequently, reduces sympathetic hyperactivation in the face of chronic stressIn short, in this study, the HRV CBKF intervention had an effect on indicators that represent ANS regulation (SDNN, LF/HF ratio and cardiac coherence), differing from placebo, reinforcing other similar findings identified in the literature