Musculoskeletal Disorders in Tyre Manufacturing Workers.

BACKGROUND: Tyre manufacturing workers are at risk of developing WRMSDs as their job repeatedly involves elevated arm postures, lifting of tyres, pushing or pulling trolleys, trunk bending and twisting. AIM: To assess WRMSDs in tyre manufacturing workers.
METHODOLOGY: This was an observational study involving 99 tyre manufacturing workers. Persons with any history of recent trauma, major hospitalization or surgery in past 12 months were excluded. Workers were screened according to Nordic questionnaire for assessing the musculoskeletal disorders and REBA analysis was done. They were also assessed for flexibility of hamstring using AKE test and isometric endurance of back extensors using Sorenson test.
RESULTS: 97% workers were under 30 years of age and 91% were males. The average duration of work was 27 months. In the past 12 months, 36% workers reported low back pain, 24.2% shoulder pain, 24.2% neck pain, 19% knee pain and 20% ankle/foot pain. REBA analysis revealed TBR and PCR manufacturing workers to be at higher and lower end of medium risk category, respectively. Average AKE values were 39.450 and 38.450 on the right and left, respectively, indicating that hamstring tightness was common, average back muscle endurance was 40.68 sec. However, AKE or back muscle endurance was not statistically related to back pain (P > 0.05).
CONCLUSION: Tyre workers showed involvement of multiple joints. LBP was predominant complaint but was not related to hamstrings tightness or back muscle endurance. Copyright:

INTRODUCTION

Work-related musculoskeletal disorders (WRMSDs) are defined as “impairments of bodily structures such as muscles, joints, tendons, ligaments, nerves, bones or a localized blood circulation system that are caused or aggravated primarily by the performance of work and by the effects of the immediate environment where the work is carried out.”[123] High- or low-intensity loads cumulatively, over a prolonged period and repeated exposure will result in most of the WRMSDs.[1] Thus WRMSDs are known to lead to reduced productivity, sickness, absence, lower quality of life, and chronic occupational disability.[4]

Esen et al.[5] have reported that 30% of MSDs identified in the world are due to work conditions, with risk factors stated as static working postures, twisting movements, speed of work, force involved, monotony, vibrations, mental pressures and lack of support. These are further influenced by the layout of the work area and loads being handled.[56]

Although tyre manufacturing industries have introduced advanced equipments with engineering controls, exposure to risk factors for developing WRMSD persists.[7]

To the best of our knowledge studies reporting WRMSDs in tyre manufacturing workers in Indian population are few. Therefore, this study aimed to assess MSDs in tyre manufacturing workers.

METHODOLOGY

This was an observational study. After approval of the Institutional Ethics Committee, young adults working in tyre manufacturing company were approached. Written informed consent was taken from all who were willing to participate and a participant information sheet explaining details of the study was given. Persons with any history of recent trauma, long period of hospitalization or surgery in the past 12 months were excluded.

There were 99 workers, all the workers were first screened by PAR-Q (Physical Activity Readiness) questionnaire and were included. Data on demographic characteristics (age, gender, number of years of work) and anthropometric dimensions such as height, body weight, body mass index (BMI) were collected. Following this, the workers were screened using Nordic questionnaire. A detailed physical examination of all the joints with provocation tests was also done.

Rapid Entire Body Assessment (REBA) was used to observe and record common working patterns/postures. Manufacturing of two types of tyres was studied, truck and bus radial (TBR) tyres and passenger car radial (PCR) tyres. The manufacturing plant categorized the work stations of TBR and PCR tyre manufacturing into two stages, I and II. REBA was conducted for both stages of TBR and PCR by a senior faculty who observed and recorded on-site work of the workers at their stations. REBA values for each task were added and the cumulative value of stage I and II of both tyre manufacturing was used for risk calculation.

Flexibility of hamstring was tested using active knee extension (AKE) test, as stated by Radwan et al.[8] The AKE measurement was defined as the degree of knee flexion from terminal knee extension which represented the amount of hamstring tightness. Sorenson test was carried out to test the isometric endurance of the back extensors as described by Biering Sørenson.[9] Endurance was evaluated in seconds by measuring how long the participant was able to hold the upper part of the body horizontal.

Statistical analysis

Results were summarized using descriptive statistics. Demographic data were analyzed using frequencies, means and standard deviations. Prevalence and other factors were analyzed using frequencies. The t test was used to see the difference between those with and without back pain. A value of P < 0.05 was considered significant for all analyses.

RESULTS

Ninety-nine tyre manufacturing workers were screened for musculoskeletal complains and included in the study.

Ninety-seven percent were under 30 years of age and 91% were males.

Seventy-six percent of workers had work experience of more than 12 months.

The mean age, BMI and duration of work is as given in Table 1.

Table 1

Mean and SD of various variables

Variable	Mean±SD
Age (years)	23.09±3.23
BMI (kg/m2)	21.25±2.63
Work duration (in months)	27±21
Hamstring tightness (Right side) (Degrees)	39.45±8.95
Hamstring tightness (Left side) (Degrees)	38.45±9.13
Back muscle endurance (sec)	40.68±25.16

Multiple joint problems (two or more than two) were present in 54 workers.

The highest prevalence of musculoskeletal disorders amongst these workers in the past 12 months was in the lower back, cervical, shoulder and ankles/feet region in the descending order and similarly, in the past 7 days, it was in the lower back, ankles/feet, knees and shoulder as seen in Figure 1.

Figure 1

Musculoskeletal symptoms in various joints in the past 12 months and last 7 days

Presence of musculoskeletal symptoms in various joints during the past 12 months and last 7 days is shown in Figure 1.

The tasks that carried more risk in developing MSDs in each stage of TBR and PCR were identified by REBA. REBA scoring and risk level are summarized in Tables 2 and 3.

Table 2

Tasks involved in TBR tyre manufacturing, REBA scoring and risk level

Stage	Task	Activity involved	REBA scoring	Risk level
TBRStage I	Bead insertion	Overhead activity/activity at shoulder level	4	Medium
	Stitching and Zipping	Wide drum requires stretching of arms, forward bending of the back with strength, zipping done at or over shoulder level as shown in figure 2	6	Medium
	Pushing/Pulling loaded trolley	Trolley mechanically loaded, weighing approx. 270 kg, pushed/pulled by the worker.	8	High
TBRStage II	Tread lifting	Overhead activity-different shoulder heights and neck angles	8	High
	Tread stitching	Reaching towards the tyre - trunk bending, arm lifting	8	High
	Checking the tyre	Trunk bending and twisting, neck bending and twisting, arm bending as shown in figure 3	6	Medium

Table 3

Tasks involved in PCR tyre manufacturing, REBA scoring and risk level

Stage	Task	Activity involved	REBA scoring	Risk level
PCRStage I	Bead insertion	Overhead activities at different heights	4	Medium
	Stitching	Trunk bending & reaching and upper arm lifting	3	Low
	Carcass removal	Handling weight with trunk bending and twisting	4	Medium
PCRStage II	Insert carcass	Handling weight with trunk bending and twisting	4	Medium
	Splicing	Trunk bending & reaching and upper arm lifting with force	8	High
	Remove green tyre	Overhead activities at different heights, trunk rotation with weight	6	Medium

Overall risk carried by TBR worker = 7 (medium risk) and by PCR worker = 5 (medium risk) as shown in tables 2 and 3.

DISCUSSION

Tyre workers in this study were young, predominantly male workers, belonging to semi-urban/rural areas, diploma holders who were in search of work experience and earnings. The mean age of the workers was 23.09 ± 3.23 years with 97% being under 30 years of age. Similar age has been reported by Alipour et al.[10] and Ghasemkhani et al.[11 Many studies report males to be mainly involved in tyre building.[111213]

According to Alipour et al.[10] 79.5% workers had a minimum of one year of work experience and Ghasemkhani et al.[11] reported the mean duration of work to be 3.9 ± 7.2 years. In this study, the average duration of work was 27 months. The duration of work could possibly explain the complaint of multiple joint pains as seen in Figure 1. According to Ghasemkhani et al.,[11] young workers in the automobile industry may, at the beginning of their careers, demonstrate musculoskeletal problems.

TBR Stage I-Stitching and zipping

The annual prevalence of neck pain in automobile/tyre manufacturing workers, as reported by various authors, ranges from seven percent to 50.98% and shoulder pain ranges from 6.1% to 76.4%.[101112131415] In this study, the prevalence of neck and shoulder pain was 13%. According to Taramsary et al.[12] combination of heavy load lifting, inappropriate postures and repetitive movements increased the risk of shoulder pain by 80% to 150%.[12] Risk factors for neck and shoulder pain as reported by various authors are age, fatigue due to work, shortage of manpower, heavy weight lifting in awkward positions, forward neck flexion, repetitive tasks and prolonged sitting.[101114]

The prevalence of musculoskeletal aches/pain in automobile/tyre manufacturing workers involving other joints is reported to be ranging from 12.8% to 52.94% at the elbow, 25.8% to 62.75% at wrist and hands, 27% to 60.3% at upper back, 19% to 60.78% at thigh/hips, 28.9% to 43.14% at knees, and 15% to 50.90% at legs and feet.[111315] In this study involvement of joints is as shown in Figure 1.

TBR stage II-Checking the tyre

This study showed highest prevalence of low back pain (LBP) over the past 12 months as well as in the past 7 days. LBP prevalence in several studies ranges from 47.4% to 72.6%.[11131516]

Manufacturing vehicle tyres (light or heavy) involves bending, twisting and turning, working with arms above shoulder level, lifting heavy weights, pushing or pulling a trolley, prolonged postures and repetitive movements with short cycle times.[11131516] All these are known to carry a low to high risk of developing WRMSDs.

REBA analysis in this study puts the TBR manufacturing workers at 7 (upper end of medium risk), and the PCR manufacturing workers at 5 (lower end) [Tables 2 and 3]. Author Esen et al.[5] assessed working postures by OWAS (Ovako Working Posture Analysing System) method. They found 10% of working postures viz. prolonged standing, bending, twisting back while carrying heavy weights and reaching. in the tyre manufacturing process to fall in risk categories 3 and 4 (highest category), similar to this in this study too, these activities were grade 6–8. These working postures have 'some' to 'very' harmful effects on the musculoskeletal system, respectively, warranting ergonomic regulations to be immediately planned and implemented.[5]

Bahardin et al.[13] also studied the prevalence of MSDs in tyre manufacturing workers and assessed their ergonomical risk level using REBA. Majority of the workers (86.3%) in their study were exposed to 'very high' (11+) and 13.7% were exposed to a 'high' level of ergonomic risk. However, they studied the most labor intensive and highly repetitive routine of manual lifting of the tread layer.[13]

LBP although has several causes, reports also suggest its correlation to hamstrings tightness and according to Radwan et al.[8] more the tightness, more the severity of LBP experienced by the patients. In this study, however, no significant relationship between tight hamstring and LBP was seen.

In this study, average back muscle endurance was 40.68 s and there was no significant relation to LBP [Table 4]. According to Demoulin et al.[17] back muscle endurance/position holding time of less than 176 sec, in males, makes them prone to LBP during the coming year whilst endurance of more than 198 sec predicts no back pain. This predictive validity does not apply to females.[17] The author also reports endurance of less than 58 sec is associated with a three-fold increase in the risk of LBP.[17] In a study done on miners, Stewart et al.[18] also did not find a statistically significant difference in position-holding time between individuals with and without a history of LBP.[18]

Table 4

Hamstring length and back muscle endurance in workers with and without low back pain in the last 12 months

Variable	Low back pain in the past 12 months	n	Mean±SD	Mean Difference	Std. Error Mean	Sig. (2-tailed)
Hamstring tightness Right side (degrees)	Yes	46	41.35±7.94	3.4610	1.1702	0.055
	No	53	37.89±9.59		1.3171
Hamstring tightness Left side (degrees)	Yes	46	40.22±8.66	3.1419	1.2763	0.088
	No	53	37.08±9.37		1.2871
Back extensor endurance (sec)	Yes	46	40.93±26.39	1.199	3.891	0.816
	No	53	39.74±24.61		3.380

It has been established that WRMSDs do not have a known specific etiology and multiple factors have been implicated. The risk factors in the tyre workers are not only associated with repetition, force, pressure, awkward and sustained postures and movements, temperatures, but may also result from the monotony of work, organizational factors, and socio-economic factors.

Therefore, while laying down strategies to prevent WRMSDs, psycho-social/organizational and individual occupational risk factors should not be ignored.

CONCLUSION

This study showed the following:

Multiple joints were involved in tyre manufacturing workers. LBP was predominant complaint

REBA analysis puts the TBR manufacturing workers to be at upper end of medium risk category, and the PCR manufacturing workers are on the lower end.

Back muscle endurance and flexibility of hamstring did not significantly correlate with back pain.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.