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Influence of stretching exercises in musculoskeletal pain in nursing professionals

Introduction: Nursing professionals (NPs) experience musculoskeletal pain that leads them to leave work. Objective: To analyze the effects of muscle stretching exercises (MSE) on pain among NPs. Method: This is a randomized controlled parallel experiment, in which 28 NPs (7 men and 21 women) were allocated into experimental (EG, n = 15; 47.4 years ± 9.5) and control (CG, n = 13; 39.15 years ± 9.6) groups. MSEs were performed for two months, three days a week, 40 min per session. A visual numeric scale was used, for which the intensity ranged from 0 (no pain) to 10 (maximum pain). The research was registered at the Brazilian Clinical Trials Registry website (TRIAL: RBR8chg6q). For statistics, the Shapiro-Wilk, T-independent and two-way ANOVA tests were applied for repeated measures with Tukey’s post-hoc test (P ≤ 0.05). Results: Most NPs work on weekends (68%) and/or have other professional activities (60.7%); 42.9% had to miss work at least once in the year prior to the survey and 66.7% of those were due to medical reasons; 42.9% work more than 10 hours/day. Of the NPs, 89.3% of the volunteers in both groups lived daily with pain in some region of the body. Pain decreased after the MSE program was initiated in the EG (p = 0.001) and differed from the CG (p = 0.002). Conclusion: MSEs were beneficial for pain reduction in NPs.


Introduction
In Brazil, the term "Nursing Professionals" (NPs) is understood as the group formed by nursing assistants, licensed practical nurses, and registered nurses, who differ in their technical qualification and their tasks assigned in a health unit [1]. The working environment makes these professionals a risk group for the development of occupational diseases [2]. Prolonged maintenance of repetitive postures and movements [3,4], accumulation of working hours, and handling improperly maintained Influence of stretching exercises in musculoskeletal pain in nursing professionals equipment (beds, stretchers, wheelchairs, etc.) are risk factors for the development of work-related diseases in NPs [5].
Nonspecific pain is multifactorial and affects several professional classes, however, Davis and Kotowski [6] indicate, through reviews, a higher prevalence of pain in NPs, especially in the lower back, regardless of personal and work characteristics.
Because NPs perform their tasks with pain, other damage, such as psychological disorders, emotional exhaustion, and suffering may affect their health [7]. Moreover, long and repetitive work schedules become a harmful and sacrificing activity for these professionals [5]. Furthermore, pain has been considered as one of the main causes of absenteeism among them [8].
To alleviate pain, exercise is considered an effective alternative [9,10], especially to lighten back pain [9,11]. Different exercise strategies have been researched for this purpose, such as Pilates, manual therapy, weight training, stretching, and Yoga, among others, in different populations of workers such as industrialists, day laborers, workpeople, and NPs [12,13].
Regarding muscle stretching exercises (MSE), positive effects on posture [13,14], blood pressure [15], increased range of motion [16], or as a complement for gym classes have been reported in literature [17]. However, for pain alleviation, such studies have no consensus [10].
The aim of this study was to determine the effects of MSE on pain in NPs. Such effects have been hypothesized to be positive, since MSE can reduce the level of activation and muscle fatigue [18,19], thus suggesting an acute effect. The chronic effect could be explained by the fact that MSE reduces muscle imbalance [20] and musculoskeletal pain, which interferes with daily living habits [21].

Method
This was a randomized, controlled, parallel experiment that followed Resolution 466 of the National Health Council of December 12, 2012 The sample consisted of 28 NPs, aged 18 to 60 years, from a population of 32 employees of a polyclinic in the city of Niterói-RJ, who experienced pain in some part of their body and were not practicing any guided physical activity in the period of participation in the research. Self-reportedly, the participants stated that they were not taking any medication or undergoing physical therapy. The volunteers were selected by convenienceafter formal invitation and individual explanation of all research procedures -, then randomly allocated to two groups: the experimental group (EG = 15), aged 47.4 ± 9.5 years, and the control group (CG = 13), aged 39.14 ± 9.6 years. The randomization process took place via software (Microsoft Excel 2010), as a way to produce low risk of bias, according to the guidelines by De Carvalho, Silva, and Grande [22].

Procedures
Before the beginning of classes, the work profile, anthropometric characteristics, and level of musculoskeletal pain of the volunteers were investigated. Immediately following the first session and at the end of eight weeks, the volunteers had their pain reevaluated. The evaluators were not blind to the group to which the volunteer belonged. Figure 1 shows the research design.
Regarding the CG, the individuals underwent the same evaluations; however, they did not participate in MSE sessions. At the end of the study, individual research volunteers were provided with individual reports containing the results of all measurements taken.
To describe the NPs profile in this study, two questionnaires were applied: the 'Well-Being Pentacle' [23], which is a model that estimates the components of lifestyle and individual well-being; and the 'Professional Data Questionnaire' [24], which seeks to answer questions about workers' functional activities.
In the anthropometric assessment, height and body mass were measured to calculate the body mass index (BMI), which was performed according to the recommendations of the International Standards for Anthropometric Assessment [25]. To do so, we used a portable stadiometer (EST 22, Cachoeira do Sul, RS, Brazil) with a maximum capacity of 2 m, a minimum of 0.3 m and an accuracy of 0.001 m; mechanical scale (Filizola, mod. 31, Osasco, SP, Brazil) with an accuracy of 100 g and a maximum capacity of 150 kg; and anthropometric tape (CESCORF Ltda., Porto Alegre, RS, Brazil), according to Silva Filho et al. [13]. For BMI, we adopted the World Health Organization (WHO) classification for adults of both sexes, which classifies the individual from 'low weight' (BMI ≤ 18.5 kg/m²) to 'grade 3  obesity' (BMI ≥ 40 kg/m²) and relates the risk of comorbidities [26].
To measure pain, we used a questionnaire consisting of closed questions regarding the presence or absence of pain, pain intensity and location, movements that aggravate pain, and a drawing in which the subjects could indicate where they were feeling pain [27].

Muscle stretching exercises (MSE)
The MSE program was conducted for 8 weeks. Each session lasted 40 minutes, consisting of active static stretching exercises with the guidance and supervision of a Physical Education teacher. Classes were offered three days a week, with a 48-hour rest between sessions, as recommended by the American College of Sports Medicine [28]. Each volunteer was to attend at least two of the sessions. The frequency of attendance of the volunteers was recorded and monitored daily by the teacher.
All sessions consisted of static and active stretching exercises for the upper limbs, trunk, hips, and lower limbs. Each exercise comprised of four sets of 30 s, with intervals of 30 s between sets.
For intensity control, the volunteers were instructed to slowly move the muscle group up to a slight discomfort to prevent possible strain. They were to remain in that position for the stipulated time. During all sessions, relaxation music was played.

Statistical treatment
Statistical calculations were performed using software (SPSS TM 21, Chicago, IL, USA), adopting a significance level of p ≤ 0.05. Initially, the Shapiro-Wilk test was used to evaluate the normality of the samples. For comparisons between the characteristics of the groups, an independent T-test was applied and, to check the group versus pain interaction, the two-way ANOVA test for repeated measures was used with the post-hoc test. Figure 2 shows the flowchart of the volunteers who were evaluated by the eligibility criteria adopted for this study.

Results
Influence of stretching exercises in musculoskeletal pain in nursing professionals 5 The anthropometric characteristics of the sample are described in Table 1, in which the groups showed a significant difference only in age (p = 0.03).
Regarding the work profile of the NPs in both groups, Figure 3A shows a large percentage of NPs working on weekends and/or other professional activities. In addition, it states that approximately half of them had to be absent for health reasons without specifying the medical reasons for such. Figure 3B shows results regarding the time and type of service of the NPs.
As for pain, it was observed that 89.3% (n = 25) of the volunteers of both groups lived daily with pain in some region of the body at the beginning of the study, with the lower back being the place of highest pain incidence (68%, n = 19), followed by shoulder blades (32%, n = 9) and shoulders (21%, n = 6). The 2 × 3 ANOVA F result with repeated measures for group versus pain interaction is shown in Figure 4, with a statistically significant difference (F = 6.5; p = 0.002), verified by Tukey's post hoc -Honestly Significant difference (HSD) for unequal samples. The groups were homogeneous regarding the initial pain symptom and, only in the EG, the acute and chronic pain were significantly lower than the initial pain (p = 0.001).
As for pain, it was observed that 89.3% (n = 25) of the volunteers of both groups lived daily with pain in some region of the body at the beginning of the study, with the lower back being the place of highest pain incidence (68%, n = 19), followed by shoulder blades (32%, n = 9) and shoulders (21%, n = 6). The 2 × 3 ANOVA F result with repeated measures for group versus pain interaction is shown in Graph 1, with a statistically significant difference (F = 6.5; p = 0.002), verified by Tukey's post hoc -Honestly Significant difference (HSD) for unequal samples. The groups were homogeneous regarding the initial pain symptom and, only in the EG, the acute and chronic pain were significantly lower than the initial pain (p = 0.001).

Discussion
This study aimed to check the acute and chronic effects of MSE on pain in NPs. The main findings were that nearly 90% of the subjects lived daily with musculoskeletal pain, especially in the lower back. This corroborates other studies that also found a high incidence of pain in NPs [3,29]. Magnago et al. [29] studied a group of 491 NPs and found that the most prevalent site of pain was in the lower back region, present in 71.5% of volunteers. One explanation can be attributed to the anatomy of the lumbar vertebrae that makes the region conducive to the incidence of spinal injuries [30]. In other words, due to their morphological characteristics, besides protecting the spinal cord, the lumbar vertebrae can withstand high mechanical loads and have great mobility while maintaining stability for trunk and hip movement. Tension, compression, and shear or torsional forces are constantly supported by the lower back region, which makes them a risk zone for injuries. Therefore, they have a differentiated anatomy compared to other spinal vertebrae [31].
The mechanisms of musculoskeletal injury are related to the types of forces involved in performing movements or maintaining postures [32]. In the spine, flexion movements generate compression in the tissues, while extension movements cause traction in the region. In addition, the shear in intervertebral discs added to the posterior fissure and weakness of the fibrous ring leads to initial disc injury and posterior protrusion of the nucleus pulposus [30]. Considering the existence and role of intervertebral discs in spinal kinesiology, such forces combined and/or applied repeatedly, with or without the presence of overloads, may trigger intervertebral disc injuries, causing pain [30,32].
The etiology of musculoskeletal pain seems unknown [33], but physical exercise is considered an effective non-pharmacological strategy for pain relief [9,10]. In this study, it was noted that both the acute effect of one exercise session and the chronic effect after 8 weeks generated a significant reduction in pain level. In the EG, initially, 93.3% of volunteers felt back pain and, after the intervention, acutely and chronically, this percentage decreased to 73.3% and 80%, respectively. That is, there was a 20% reduction in people who felt pain in the EG and 13% in the CG. In its acute effect, MSE may reduce the level of muscle activation and fatigue, and in its chronic effect, MSE may attenuate muscular imbalance, factors which are closely linked to the sensation of pain [19][20][21].
The beneficial effect of exercise on the sensation of pain observed in the NPs, in this study, confirms the findings of literature. An Asian survey by Chen et al. [34] verified the effectiveness of an MSE program on lower back pain in 127 NPs, separated into EG and CG, followed for 24 weeks; in the study, the EG showed significantly lower pain scores than the CG after the intervention. This type of intervention has also been investigated in other individual profiles and the results have also been positive, similar to the study by Puppin et al. [33], in which the effect of 8 weeks of MSE in 55 patients with back pain was evaluated, and the outcomes showed a significant reduction in pain in the EG compared to the CG. In another study, conducted with 31 women allocated to either the EG and CG, after 6 weeks of MSE, patients with back pain had decreased pain sensations at the end of the study when compared to the CG [11].
MSE proved to be efficient and might be a means of intervention in individuals with pain, which positively interferes with their daily living and work activities [21,29]. On the other hand, the possible placebo effect that the intervention may have had on volunteers should be considered. In this regard, Lindheimer, O'Connor, and Dishman [35] pointed out that the placebo effect accounts for about 50% of the psychological benefits seen as a consequence of physical training. However, both for a better understanding of the placebo effect related to exercise and the mechanisms involved in occupational pain, further studies are needed.
This study showed relevant information on the role of physical exercise in the occupational health of nursing professionals, a group that is at risk for the development of occupational diseases, but which, however, has a large representativeness in the workforce in the health area. Although the sample size was small, the findings corroborate what literature already indicates regarding the benefits that physical exercise may generate in the individual's health. Even if the placebo effect is considered, regular physical activity constitutes a healthy lifestyle and should also be promoted to health professionals as a way to take care for themselves as they take care of others.

Conclusion
This study concluded that for this NP sample, MSE promoted positive changes, reducing the level of musculoskeletal pain soon after one session and after 8 weeks of training.
Influence of stretching exercises in musculoskeletal pain in nursing professionals