Analysis of the association between high workload and musculoskeletal pain in public school teachers according to physical activity level

Abstract

BACKGROUND:

A high workload has been associated with musculoskeletal pain in public school teachers. However, the hypothesis of the present study was that physical activity (PA) practice is able to attenuate this association.

OBJECTIVE:

To analyze the associations between high workload with musculoskeletal pain according to PA levels in public school teachers.

METHODS:

Teachers (n = 239) from 13 public schools were evaluated. Workload was assessed using a Likert scale in which teachers reported their perception of their work routine as: very low, low, regular, high, and very high. Musculoskeletal pain and PA were assessed using questionnaires. Multivariate logistic regression models were used to investigate the association of high workload with PA levels and musculoskeletal pain in different body regions, compared to participants with normal workload, adjusted by sex, age, and socioeconomic status.

RESULTS:

A high workload was associated with higher chances of reporting pain in the wrists and hands (OR = 3.55; 95% CI = 1.27–9.89), knee (OR = 3.09; 95CI% = 1.09–8.82), and feet and ankles (OR = 3.16; 95% CI = 1.03–9.76) in less active teachers. However, these associations were not observed in teachers considered more active.

CONCLUSION:

PA practice is able to act as a good protector against musculoskeletal pain in teachers, even in individuals with a high workload.

Keywords

Workload school teachers musculoskeletal pain physical inactivity epidemiology public health

1 Introduction

The number of studies that address the relationship between health and workload has grown lately due to the volume of evidence demonstrating that this association impacts individuals’ lives [1]. School teachers correspond to an occupational class of professionals who are constantly exposed to long workloads in order to exercise of their profession [2]. According to the results obtained by the Organization for Economic Cooperation and Development (OECD) Teaching and Learning International Survey, an international survey carried out in 2018 with a large scale of teachers [3], the global average workload of a teacher is 38.3 hours per week [2, 3].

In Brazil, in a recent survey carried out by the Brazilian Institute of Geography and Statistics (IBGE) in 2020, the average workload of teachers was 34.6 hours per week [4]. However, teachers’ daily activities are not restricted to work that takes place within classrooms, due to their need to prepare activities, plan classes, correct work and tests, and prepare other didactic content to be administered to students, which necessitates that teachers have an additional workload to carry out other activities in their respective homes [5], exceeding the maximum workload legally established worldwide of 40 hours per week. Teachers who exceed these values are associated with a higher prevalence of developing health problems, such as mental impairments, insomnia, and musculoskeletal disorders [6].

Long working hours lead to these teachers acquiring some static postural addictions and/or repetitive movements for a long period, in order to perform their activities. The main postural vices highlighted are the long-standing periods to teach classes, sitting to correct activities and/or use the computer, the low cervical inclination during reading and writing, and prolonged flexion of the upper limbs related to writing on the blackboard. Kindergarten teachers have additional postural vices, such as remaining seated on small pieces of furniture or even on the floor with a trunk inclination above 20 degrees and long periods of crouching and/or kneeling [7 –9]. Given the above, teachers have a high occupational risk of developing musculoskeletal injuries, denominated work-related musculoskeletal disorders (WMSD), with a prevalence of from 39 to 95%. WMSD are injuries that the individual acquires, depending on working conditions, through exposure to the environment and activity. The correlation between WMSD and teachers occurs due to ergonomic changes in the work environment, combined with low pay and work overload, resulting in occupational stress, which is reflected in the development of WMSD [10 –12].

The permanence of these postures for a long time, contributes to high rates of pain in various regions of the body. Studies point out that the places with the highest prevalence of pain are in the lower lumbar region (45.6 to 68%), upper back region (27.6%), neck (27.2 to 60.1%), shoulders (31.6 to 63.4%), wrist (16.2 to 56.7%), lower limbs (19.1 to 40%), and ankle (24%) [13 –15]. Chronic pain is strongly linked to the salaried adult population, including teachers, especially in low and middle-income countries [16].

Studies indicate that physical activity is essential for preventing cardiovascular disease, due to its ability to increase insulin sensitivity and reduce adiposity [17], preventing musculoskeletal pain and improving quality of life by increasing muscle strength and flexibility [18, 19]. However, there are still not enough studies that report whether the practice of physical activity has the potential to mitigate the relationship between extensive workload and musculoskeletal pain in public school teachers. Therefore, the current study aimed to verify musculoskeletal pain and analyze the associations with high workload and physical activity levels in public school teachers.

2 Methods

2.1 Design and sampling process

This was an observational study with a cross-sectional design involving public school teachers from the city of Presidente Prudente, located in the Southeastern region of Brazil. Among the 23 public schools that exist in the municipality, 13 agreed to participate in the study after personal contact with the school managers.

Aiming to select teachers from the different regions of the city, the 13 public schools were divided according to geographical region of the city (north, south, east, west, and central), where two schools from each region were selected and all the teachers in the selected schools were invited to participate. The minimum sample size was calculated for a larger research project that encompassed aspects of health behaviors in teachers, which considered a prevalence outcome of 50%, adopted in epidemiological studies with an unknown prevalence or different outcomes [20], a population of 650 teachers from the public school in the municipality, a CI (confidence interval) of 95%, test power of 80% and tolerable error of 5%, which provided a simple random sample of 242 teachers. Individuals were considered eligible to participate in the research if they had a tenured teaching position in a school, agreed to participate in all study procedures, and signed the informed consent form. This research was previously approved by the Ethics in Research Committee of São Paulo State University (UNESP).

2.2 Instruments and procedures

Initially, an individual interview was conducted to collect personal data and verify the inclusion criteria, followed by an assessment of anthropometry (weight and height), socioeconomic status, sedentary habits, and musculoskeletal pain, performed by previously trained professionals in a specific room provided by the institution.

2.2.1 Workload

Workload was assessed using a Likert scale on which teachers reported their perception of their work routine as: very low, low, regular, high, and very high. Teachers who reported very low, low, or regular were classified as having a normal workload, while those who reported high or very high were classified as having a high workload. The perception of workload was adopted in this study to better understand the total load (at school and at home) of the teacher.

2.2.2 Nordic musculoskeletal questionnaire

The Nordic Musculoskeletal Questionnaire [21] was used to assess the bodily pain in the sample. Data collection was carried out through self-reporting of pain by individuals in the nine mapped regions of the body (neck, shoulder, upper back, elbow, hand and wrist, lower back, hip, knee, foot and ankle) related to the previous 7 days. This instrument was tested and presented good reliability in the Brazilian population [22].

2.2.3 Anthropometry

Anthropometry was assessed with participants barefoot and wearing light clothes. To avoid possible constraints in the collection of anthropometric data, male teachers were evaluated by male researchers and female teachers by female researchers. Body weight was measured using a Plenna® digital scale with a precision of 0.1 kg and a capacity of 180 kg and height was measured using a Sanny® portable stadiometer with a precision of 0.1 cm and a total height of 2.20 meters. After obtaining these two measurements, the body mass index (BMI) was calculated by dividing body weight by the square of height (BMI = kg/m2) [23].

2.2.4 Socioeconomic status

The Brazilian Economic Classification Criteria, originated from the Brazilian Market Research Association (ABEP) [24], was used to assess the socioeconomic status of the sample. For the classification, questions related to the level of education and the presence and quantity of some attributes in the household and household appliances are considered, such as the number of bathrooms, TV, freezer, car, and washing machine. Based on the scores obtained in the requirements, the socioeconomic classification is established according to the score, in descending order A1, A2, B1, B2, C1, C2, D-E. The individuals who made up the study were classified as having high socioeconomic conditions if they scored in classes A1 and A2, medium socioeconomic conditions from B1 to C1, and low socioeconomic conditions from C2 to E.

2.2.5 Habitual physical activity

The habitual practice of physical activity was assessed using the questionnaire proposed by Baecke et al. [25]. The questionnaire consists of 16 questions divided into three different domains: physical activity at work with 8 items, sports at leisure with 4 questions, and physical activity at leisure excluding sports with 4 questions. The score for each domain ranges from 1 to 5, obtained through a specific formula that takes into account various indicators of the practice of physical activity (frequency, intensity, duration), where the sum of the three domain scores results in the total physical activity score. The Baecke score corresponds to a dimensionless value without a specific metric, such as minutes, or to a Metabolic Equivalent of Task (METs) measure that indicates the amount of energy expended during a given physical activity compared to energy expenditure at rest, where the higher the score, the higher the physical activity level [26]. Due to the lack of a cut-off point for determining physically active individuals, participants above the 75th percentile of the Baecke score were classified as more active, while those below the 75th percentile were classified as less active.

2.3 Data analysis

Sample characteristics were expressed as mean and standard deviation for continuous variables and as frequency and proportion for categorical variables. Means were compared using the t-test for independent variables and categorical variables were compared using the χ2 test. Multivariate logistic regression models were used to investigate the association of high workload with physical activity levels on musculoskeletal pain in different body regions (outcome), compared to participants with normal workload. Musculoskeletal pain was accounted for according to the occurrence of pain in different body regions as an outcome, physical activity levels as an independent variable, and sex, age, and socioeconomic status as covariates. The significance level was set at p < 0.05 and the confidence interval adopted was 95%. All analyses were performed using IBM SPSS Statistical Package, version 25.0.

3 Results

In total, 239 public school teachers participated in this study. Information on sample characteristics according to weekly workload are shown in Table 1. On average, teachers with a high workload taught an additional 7 hours in classes per week.

Table 1
Sample characteristics according to weekly workload

Normal workload N = 115 High workload N = 124

Mean (SD) Mean (SD) P

Age (years) 45.31 (11.40) 44.84 (9.50) 0.729

Weight (kg) 75.41 (17.48) 73.39 (16.08) 0.354

Height (cm) 164.40 (8.80) 164.33 (8.40) 0.949

BMI (kg/m²) 27.82 (5.64) 27.08 (5.11) 0.288

Socioeconomic level (ABEP score) 26.50 (5.64) 26.33 (5.84) 0.813

Weekly workload (h/week) 33.50 (11.40) 40.99 (11.87) < 0.001

Physical activity (Baecke score) 7.43 (1.88) 7.85 (1.64) 0.106

	Normal workload N = 115	High workload N = 124
	Mean (SD)	Mean (SD)	P
Age (years)	45.31 (11.40)	44.84 (9.50)	0.729
Weight (kg)	75.41 (17.48)	73.39 (16.08)	0.354
Height (cm)	164.40 (8.80)	164.33 (8.40)	0.949
BMI (kg/m²)	27.82 (5.64)	27.08 (5.11)	0.288
Socioeconomic level (ABEP score)	26.50 (5.64)	26.33 (5.84)	0.813
Weekly workload (h/week)	33.50 (11.40)	40.99 (11.87)	< 0.001
Physical activity (Baecke score)	7.43 (1.88)	7.85 (1.64)	0.106

ABEP score: Score originating from the socioeconomic questionnaire, where the higher the score, the higher the economic class. Baecke score: dimensional score; where the higher the value, the more active the participant.

Table 2 presents the prevalence of musculoskeletal pain according to physical activity levels in teachers with a high workload. Although, in general, the prevalence of pain was higher in less active teachers, there was no statistical difference. The highest prevalence of pain was observed in the low back and shoulders, in approximately 21% of teachers considered less active.

Table 2

Prevalence of musculoskeletal pain according to physical activity level in teachers with a high workload (n = 65)

	Less active	More active	p
Neck	18.8	11.4	0.433
Shoulder	22.0	8.8	0.153
Upper back	11.0	14.7	0.795
Elbow	10.0	14.7	0.659
Wrist and hand	18.7	8.8	0.287
Low Back	20.9	14.7	0.600
Hip and thigh	11.0	2.9	0.290
Knee	8.8	5.9	0.727
Foot and ankle	17.8	5.9	0.164

Table 3

Association between workload and musculoskeletal pain according to physical activity levels in public school teachers

	Total sample (n = 239)		Less active participants (n = 174)		More active participants (n = 65)
	High workload^a (n = 125)		High workload^a (n = 84)		High workload^a (n = 41)
	OR (95% CI)	p	OR (95% CI)	p	OR (95% CI)	p
Neck	0.98 (0.41–2.33)	0.973	1.38 (0.50–3.85)	0.534	0.39 (0.07–2.10)	0.276
Shoulder	1.47 (0.65–3.30)	0.358	2.05 (0.76–5.55)	0.156	0.61 (0.14–2.71)	0.522
Upper back	0.92 (0.33–2.59)	0.876	1.17 (0.29–4.73)	0.825	0.38 (0.06–2.11)	0.267
Elbow	2.35 (0.55–9.94)	0.245	1.07 (0.28–4.12)	0.917	3.24 (0.58–17.96)	0.178
Wrists and hand	2.46 (1.03–5.87)	0.042	3.55 (1.27–9.89)	0.015	0.92 (0.16–5.37)	0.930
Low Back	1.27 (0.57–2.84)	0.555	1.61 (0.60–4.34)	0.342	0.67 (0.15–2.88)	0.671
Hip and thigh	2.60 (0.95–7.10)	0.062	2.80 (0.85–9.29)	0.090	2.02 (0.29–13.94)	0.473
Knee	1.98 (0.83–4.72)	0.123	3.09 (1.09–8.82)	0.034	0.81 (0.15–4.50)	0.815
Foot and ankle	3.34 (1.41–7.90)	0.006	3.16 (1.03–9.76)	0.045	3.87 (0.83–17.92)	0.084

Adjusted by sex, age, and socioeconomic condition. a: Participants with normal workload were the reference category; CI: Confidence interval.

When considering the total sample, teachers with a high workload were more likely to report pain in the wrists and hands and feet and ankles. Considering less active teachers, a high workload was associated with greater chances of having pain in the wrists and hands (approximately 3 times more likely). Similar findings were also observed for knee pain (OR = 3.09) and for foot and ankle pain (OR = 3.16). However, these associations were not observed in teachers considered more active.

4 Discussion

The present study aimed to verify whether a high workload is associated with musculoskeletal pain in public school teachers and whether these associations are different considering physical activity levels. The prevalence of musculoskeletal pain, in general, was higher in more physically inactive teachers. Furthermore, a high workload was associated with musculoskeletal pain in three different body regions in less active teachers, but in more active teachers, these associations were not observed.

The present study verified the existence of an association between a low level of physical activity and musculoskeletal pain in different parts of the body, with emphasis on the wrists and hands, knees, and feet and ankles. Studies indicate that musculoskeletal pain is correlated with the intensity, frequency, and duration of exposure through a task, and that it can be alleviated by the level of physical activity. Physical activity performance has a protective factor for pain, which justifies pain in the wrists and hands in teachers with a low level of physical activity, since the activities developed by teachers require a lot of manual work [27 –29].

Regarding pain in the lower limbs (knees, feet and ankles), a prospective study by Goossens et al. [30] with teachers in Belgium found that the knee is one of the most injured regions in these individuals. Pain in this region is strongly related to the use of inadequate shoes and a prolonged standing time [31]. These factors are also strongly related to high rates of pain in the feet and ankles, as evidenced in the cross-sectional study by Alrashidi et al. [32] carried out with teachers in Saudi Arabia, where pain levels were higher in public school teachers and with low levels of physical activity.

Furthermore, although not significant, it was possible to observe that teachers with a greater workload and high levels of physical activity had higher Odds values for musculoskeletal pain in the elbow and foot and ankle regions when compared to less active teachers. The possible justifications for these findings are related to prolonged activity in the performance of the profession, which leads to fatigue and, consequently, the degeneration of muscle fibers [33, 34]. Moreover, a shorter and insufficient recovery time increases the injury potential. In addition to this relationship, physical activity, although very beneficial, can overload these already fatigued muscle groups [35]. According to the study of Grandou et al. [36], it is extremely important that the muscle, after overload, has adequate rest periods for better recovery, which may not occur with physically active teachers with a high workload.

The role of physical activity as a protective factor for musculoskeletal pain can be outlined by different mechanisms. The hypoalgesia induced by physical activity can be an endogenous pain modulator [37] and is also able to reduce pain sensitivity [38]. Physical activity contributes to noradrenergic system activation, releasing catecholamines and upregulating its receptors in the nervous system, acting on the central nociceptive modulation of pain [39]. Physical activity has also shown an immunomodulatory effect, by reducing inflammatory levels and, consequently, body pain [40]. In addition, physical activity improves bone health and minimizes bone loss in the aging process [41], as well as contributing to physical fitness maintenance, and to the performance of daily activities with better resistance and strength [42]. Physical activity can also contribute to better posture, due to improved activation of postural muscles during standing and walking, such as abdominal, multifidus, and paraspinal muscles [43], contributing to the prevention and minimization of body pain.

In addition, studies show that strengthening exercises are effective in preventing and reducing musculoskeletal pain, when performed correctly. Furthermore, exercises focusing on physical conditioning and with vigorous intensity result in positive effects on pain, making these good exercise options for less active teachers [44, 45]. Labor Gymnastics gained visibility due to its effectiveness in reducing pain, and ability to be performed in workplaces, making exercise more accessible to everyone [46].

Among the potential measures to reduce the high workload of teachers, it is possible to list salary adjustments, as many teachers need to work more due to socioeconomic conditions [47]. As intervention measures, Labor Gymnastics are recommended, supervised by a qualified professional, which provide better physical conditioning to support the postures required at work [46]. Improvements to the infrastructure where teachers teach their classes could also help ease the workload.

Among the limitations of the present study, the cross-sectional design should be pointed out, since the cross-sectional design does not allow for cause and effect analyses. Another point is the fact that physical activity was assessed using a questionnaire, which may be inherent to memory bias. Residual confounding can be attributed to the lack of information about physical activity determinants in the sample, as pleasure in the practice, influence of family and peers, as well as environmental factors, may influence physical activity level besides the workload of teachers. However, as positive points, we emphasize that teachers were evaluated from schools in different regions of the city where the study was carried out.

5 Conclusion

The association between high workload and musculoskeletal pain was observed only in less active teachers. Therefore, increments to increase the practice of physical activity in these professionals should be encouraged. Furthermore, we emphasize the importance of reducing the high workload of teachers.

Ethical approval

São Paulo State University (CAAE:45486415.4.0000.5402).

Informed consent

All participants agreed to participate in the study and signed a consent form.

Conflict of interest

The authors declare they have no conflict of interest regarding this study.

Footnotes

Acknowledgments

We would like to thank all the teachers who agreed to participate in this study.

Funding

DGDC holds a Productivity Fellowship from the National Council for Scientific and Technological Development (CNPQ; Grant number: 305886/2022-3). This study was funded by the Coordination for the Improvement of Higher Education Personnel (CAPES), Brazil (code 001).

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