Incidence of low back pain according to physical activity level in hospital workers

BACKGROUND AND OBJECTIVES: Hospitals integrate several risks posed by physical, chemical, psychosocial and ergonomic factors, which may be noxious for different healthcare professionals. This study aimed at evaluating the level of physical activity, the presence of musculoskeletal risk factors and the incidence of low back pain among nursing professionals of a hospital Materials and Sterilization Center. METHODS: Sample was made up of 56 individuals of both genders, working for the Associação Beneficente de Campo Grande/MS-Hospital Santa Casa. Participants were divided in two groups: G1 (insufficiently active, n=27) and G2 (sufficiently active, n=29). In addition to the level of physical activity, anthropometric data, incidence of pain and functional incapacity, flexibility and muscle resistance were evaluated. RESULTS: The incidence of low back pain was lower in G2 (13 cases; 44.8%) as compared to G1 (24 cases; 88.9%). Body mass index, pain intensity and functional incapacity index were lower for G2. Time of physical activity was lower in G1. Abdominal muscles resistance was higher in G2. CONCLUSION: In nursing professionals, the level of physical activity influences the presence of low back pain, pain intensity and functional incapacity index.


INTRODUCTION
Low back pain is a major public health problem, reaching epidemic levels among general population, affecting economically active people and considered the most important reason for medical leave 1 .Pain is multifactorial, involving individual, psychosocial, occupational, genetic, and biomechanical factors.Among intrinsic risk factors there are age, gender, body mass index, muscle imbalances and sedentary life 2 .Low back pain induced by mechanicalpostural conditions is responsible for a large part of back pain referred by population 1 .Postural stress may change several musculoskeletal system structures, generating imbalances and decreasing muscle strength.Loss of flexibility, regardless of cause, may also induce pain and decrease muscle strength 1,2 .Extrinsic factors, such as labor-related functional overload 1 , may also contribute for low back pain development and worsening.Hospital environment poses several risks caused by physical, chemical, psychosocial and ergonomic factors, which may be noxious to the health of professionals of the area 3 .Among professionals working in hospitals, nurses are professionals more often affected by low back pain, with high incidence rate and prevalence per year 3 .Their work is not limited to direct patients' assistance, but rather is extended to indirect assistance by means of Central Materials and Sterilization Department (CMSD).This is a technical support sector, mostly made up of nurses and aimed at receiving contaminated materials, decontaminating them, preparing and sterilizing them, as well as at preparing and sterilizing clean clothes coming from the laundry and storing such materials for future distribution 4 .
Considering the high incidence of low back pain among nurses and the scarcity of CMSD-related studies, this study aimed at evaluating the level of physical activity, the presence of musculoskeletal risk factors and low back pain among nurses of a hospital CMSD.Additionally, the association between these potential risk factors and the incidence of low back pain was investigated.  1 shows demographic and anthropometric variables.There has been no significant difference between groups for height and body mass index (BMI).Age and BMI were lower for G2.As to low back pain, after fixing the group, there has been significant difference in G1, with predominance of individuals with low back pain.In G2 there has been no difference between presence and absence of low back pain.There has also been difference between groups with regard to the incidence of low back pain, being the number of positive cases higher in G1 and the number of negative cases higher in G2.
Table 3 shows data on time of physical activity practiced per week, musculoskeletal risk factors for low back pain, low back pain intensity and functional capacity index, according to group.G2 had longer total physical activity time per week as compared to G1.In addition, pain intensity and functional incapacity index were higher in G1 as compared to G2.With regard to musculoskeletal risk factors for low back pain, the number of repetitions performed during maximum repetition test for abdominal muscles was higher for G2 as compared to G1.However, there has been no significant difference between groups for values of the sit and reach and Thomas tests for lower limbs.
With regard to sit and reach test, individuals were classified by the level of flexibility and both groups had values compatible just with classifications "below average" and "poor".In G1, 3 individuals (11.1%) were considered below average and 24 (88.9%) with poor performance.In G2, 4 individuals 13.8%) were considered below average and 25 (86.2%) with poor performance.At Goodman test, when fixed the group, the number of individuals with poor performance in the sit and reach test was significantly higher than the number of individuals with performance below average in both groups.However, there has been no difference in the number of cases of hip flexors shortening (Table 4).

DISCUSSION
CMSD is a technical support sector, primarily made up of nursing professionals, which works around-the-clock to supply the demand of different hospital sectors 4 .Among CMSDrelated ergonomic risks there are accelerated working rhythm, information flow, job organization, upright or static posture for long periods, repetitive upper limbs movements and hard work 11 .The exposure of people to extrinsic and intrinsic risk factors promotes acute body response, characterized by fatigue, discomfort and pain for prolonged periods.In addition, there may be adaptation mechanisms or the development of chronic effects, peaking with Work-Related Musculoskeletal Disorders (WRMD), such as low back pain [1][2][3] .Although being considered multifactorial, low back pain etiology is frequently associated to sedentary life, reflecting the combination of deficient musculoskeletal fitness and lumbar region overload 1 .In our study, the incidence of low back pain was higher in the insufficiently active group.Adequate fitness levels may contribute to maintain body posture during routine functions with lower energy waste, without exceeding tolerable musculoskeletal limit.Physical activity also attenuates major risk factors involved with low back pain syndrome, such as muscle weakness, especially in the abdominal region, and poor joint flexibility of dorsum and lower limbs 12 .Petersen & Marziale 13 have observed lower frequency of low back pain in nurses practicing sports.Interestingly in our study, not only low back pain but also pain intensity was lower in the sufficiently active group.
In the biochemical context, trunk muscles weakness is a major risk factor for low back pain.Especially abdominal muscles play a critical role in spine and pelvic girdle stabilization.When there is abdominal weakness, there is hip instability, allowing the psoas muscle to anteriorly traction lumbar vertebrae, leading to pelvic anteversion and increased lumbar lordosis 9,12,14  Chronological age is associated to physical activity decline, thus increasing the risk for low back pain 1,10 .In addition, it is well established that aging is associated to degenerative changes in lumbar spine structures, which may cause pain, decreased flexibility and muscle weakness 10 .Overweight may be considered independent low back pain factor because it increases abdominal circumference worsening pain and may associate it to lumbar spine changes.According to Heuch et al. 2 low back pain is associated to BMI and pain intensity increases as the level of obesity progresses.In addition, CMSD workers carry heavy objects every day during work, which may lead to anterior gravity center shift, generating pelvic anteversion and consequently increased lumbar lordosis.

CONCLUSION
Among nurses working in a hospital CMSD, the level of physical activity influences the incidence of low back pain, pain intensity and functional incapacity.In addition, sufficiently active individuals have better abdominal muscles resistance.
5935/1806-0013.20170003Incidence of low back pain according to physical activity level in hospital workers Rev Dor.São Paulo, 2017 jan-mar;18(1):8-11 1,3ed on studied population, with 87 individuals, to determine sample size, prevalence of 90% of professionals with history of occupational low back pain was established1,3, with significance level of 95% and admitting sample error of 5%.With this, minimum of 54 participants were obtained to develop the study.This study was approved by the Research Ethics Committee, Universidade Federal de Mato Grosso do Sul, opinion 545.584.Results are presented in descriptive format.Student t test for parametric data and Mann Whitney test for non-parametric data were used to compare between groups.Goodman test was used for proportion analyses.Significance level was 5%.
10d cross-sectional study with nurses of both genders, working in the CMSD of the Associação Beneficente de Campo Grande -Hospital Santa Casa, Campo Grande/ MS.Inclusion criteria were minimum age of 18 years and minimum experience of six month on the job.9.Muscle resistance was evaluated with Maximum Repetition test in one minute for abdominal muscles10.RESULTSStudy sample was made up of 56 individuals who agreed to participate in the survey.From these, 43 were nursing technicians (76.8), 11 were nursing assistants (19.6%) and 2 were nurses (3.6%).With regard to shift, 22 (39.3%)worked in the morning, 18 (32.1%) in the afternoon and 16 (28.6%) in the evening.As to weekly workload, 43 (76.8%)worked 42 weekly hours and 13 (23.2%)had double jobs, in a total of 74 to 84 weekly hours.Among individuals with double jobs, 69.2% (n=9) worked as nursing technician, 15.

Table 1 .
Demographic and anthropometric variables according to the level of physical activity

Table 4 .
Number of cases of hip flexors shortening according to the level of physical activity G1 = group of insufficiently active individuals; G2 = group of sufficiently active individuals; RLL = right lower limb; LLL = left lower limb; Goodman test; A, B = for vertical comparisons; a = for horizontal comparisons; different letters mean significant difference (p<0.05).

Table 3 .
Physical activity practiced per week, low back pain intensity, functional incapacity index and musculoskeletal risk factors for low back pain, according to the level of physical activity.

Table 2 .
Proportion of low back pain cases according to the level of physical activity G1 = group of insufficiently active individuals; G2 = group of sufficiently active individuals; Goodman test; A, B: for vertical comparisons; a, b: for horizontal comparisons; different letters mean significant difference (p<0.05).
12 is possible that part of the differences found between some studies is due to the way flexibility was evaluated.Although being easy to apply with high reproducibility, sit and reach test is considered an indirect and linear test characterized for expressing results in a distance scale.Linear tests have as weakness the incapacity of giving a global vision of individu-al's flexibility and the possible interference of anthropometric variables on tests results12.As to demographic and anthropometric variables, sufficiently active individuals had younger age and lower BMI.