Under the Hood – Decoding Musculoskeletal Health among Vehicle Mechanics in Urban Mumbai: A Cross-Sectional Study

Abstract

Background:

Work-related musculoskeletal disorders are a significant cause of ill health among working populations. Vehicle repair mechanics are at high risk due to their work nature.

Objectives:

To investigate the prevalence, pattern, and severity of musculoskeletal disorders among automotive repair mechanics in Mumbai, India, and to analyze associated postural risks.

Methodology:

A cross-sectional study was conducted on 423 garage mechanics in Mumbai. Data were collected using a self-administered questionnaire. Postural risks were analyzed using the Rapid Entire Body Assessment (REBA) scale. Joint angles were measured using Kinovea software. Descriptive statistics and correlation analyses were performed.

Results:

Among 423 mechanics, 23 (5.4%) reported pain, primarily in the lower back (26.1%) and knees (34.8%). The median age was 29 years (IQR: 9). Most mechanics worked 10–12 h daily (51.1%), 7 days a week (70.4%). REBA scores were significantly correlated with trunk posture (r = 0.645, P = 0.001) and Score A (r = 0.85, P < 0.001). Lower back pain showed a positive correlation with REBA scores (r = 0.050, P = 0.819).

Conclusions:

The prevalence of musculoskeletal pain among vehicle repair mechanics in this sample was relatively low. However, those who reported pain primarily experienced lower back and knee pain. Postural risks, particularly trunk posture, were significantly associated with overall ergonomic risk.

INTRODUCTION

Vehicle repair mechanics perform essential maintenance work including inspection, cleaning, repairing, rebuilding, and testing across various maintenance systems in the automobile industry.[1] This occupation frequently requires workers to adopt challenging postures such as kneeling, squatting, stooping with forward flexion, and awkward hand and shoulder positions. Additionally, mechanics often perform emergency roadside repairs, requiring rapid adaptation to unpredictable environments. This predisposes the mechanics to think on their feet in order to adapt to the situations. These physical demands and working conditions potentially expose mechanics to significant musculoskeletal risks, warranting investigation into the prevalence and patterns of musculoskeletal disorders in this population.

Work-related musculoskeletal disorders (WMSDs) are a significant occupational health concern, particularly in developing countries. Ergonomic factors such as working postures, static load, and task invariability are leading causes for WMSDs. Vehicle repair mechanics are at high risk due to the physical demands of their work, including awkward postures, repetitive movements, and manual handling of heavy objects as illustrated in Figure 1.[2,3] Previous studies have reported prevalence rates of WMSDs among automotive mechanics ranging from 15% to 92%, depending on the body region and population studied.[4] However, data from India, particularly Mumbai, are limited. Being a metropolitan city with an abundance of vehicles from vintage to modern categories, it is imperative that we delve deeper into the mechanics and their musculoskeletal health.

Figure 1.

Mechanic repairing a car

WHO (2021)[5] released a fact sheet identifying that musculoskeletal conditions are a leading cause of disability worldwide impacting mobility, dexterity, and overall quality of life. They also represent a significant cause of work absence and reduced productivity in industrial settings.

This study is thus aimed to determine the prevalence of musculoskeletal disorders among vehicle repair mechanics in Mumbai to identify the most common sites of pain and their severity. This study also has the objective to analyze the postural risks associated with the work of vehicle repair mechanics and investigate the relationship between postural risks and reported pain.

METHODOLOGY

This study was presented and approved by the Institutional Research Review Committee (MGM/COP/IRRC/2/2022). The participants were selected, and the study commenced after obtaining written informed consent from each one.

Study design and setting

This cross-sectional study was conducted among vehicle repair mechanics working in garages across various regions in Mumbai, India. Garages were selected randomly from different zones (Western, Central, Eastern, Harbor) across Mumbai. Garage size was also considered during selection. A sample size of 423 participants was determined using a convenient sampling method.

Participants eligible for inclusion were all vehicle repair mechanics aged 18–50 years, working in garages across Mumbai. The older mechanics were excluded so that the effects of aging do not mask the findings of this study. Exclusion criteria were any musculoskeletal injury in the past 6 months outside the work environment and any neurological affection in the past 6 months.

Variables

The primary outcome was the presence of musculoskeletal pain, assessed using the Modified Nordic Questionnaire. The Nordic Questionnaire was developed as a tool to evaluate musculoskeletal dysfunction in various occupations. It has two sections: Section 1 focuses on identifying areas of the body causing musculoskeletal problems, while section 2 has additional questions relating to the neck, the shoulders, and the lower back, which further detail relevant issues. Respondents are asked if they have had any musculoskeletal issues in the past 12 months and the past 7 days, which has prevented normal activity.[6]

Secondary outcomes included pain intensity [measured on a Numerical Rating Scale (NRS)] and postural risk (assessed using REBA). In an NRS, participants are asked to circle the number between 0 and 10. Zero usually represents ‘no pain at all’, whereas the upper limit represents ‘the worst pain ever possible’.[7]

The Rapid Entire Body Assessment (REBA)[8,9] is an ergonomic evaluation method created by Hignett and McAtamney to evaluate full-body postures and their associated risks of WRMSDs. This tool was designed to address the need for a practical field instrument capable of analyzing the unpredictable postures often encountered in healthcare and service industries. The REBA process involves assigning scores to different body regions for each task analyzed. It divides the body into two groups: Group A (trunk, neck, and legs) and Group B (upper arms, lower arms, and wrists), assessing both left and right sides. Each region is scored based on posture, with additional adjustments for specific factors.

The assessment also considers load/force and coupling factors. After scoring individual components, the evaluator consults Table A for Group A scores and Table B for Group B scores. Score A is calculated by adding the Table A score to the load/force score, while Score B combines the Table B score with the coupling score for each hand. These results are then used to determine Score C using Table C. The final REBA score is obtained by adding Score C to an activity score. This total score corresponds to a risk level on the REBA Decision table, indicating the degree of WRMSD risk associated with the assessed posture.

Based on the pilot study conducted on 15 participants to find out the most painful positions and explore the tasks performed by the mechanics, two positions were identified: stooping and squatting, which are the positions commonly adopted while repairing the vehicle. Hence, these two positions were chosen for REBA analysis through photogrammetry using Kinovea Software as illustrated in Figure 2.

Figure 2.

Photogrammetric evaluation for REBA analysis

The key exposure variables included are work hours, years of experience, types of tasks performed, and postures adopted. These were collected in the form of a self-made questionnaire. A series of background and demographic items including age, highest education attainment, and job-related questions such as work experience and hours of mechanic activities per day were evaluated using a questionnaire. The questionnaire was developed and face-validated before the final version was used in the study for data collection.

Data sources/measurement

Data were collected using a self-administered questionnaire. Postural assessment was conducted using REBA, with joint angles measured using Kinovea software.

Bias

To minimize recall bias, we limited pain assessment to the past 12 months and 7 days. Selection bias was addressed by including all eligible mechanics in the selected garages. The sample included mechanics from both small-scale and large-scale garages, ensuring diverse workplace representation. The study included mechanics engaged in the repair and maintenance of two-wheelers, light motor vehicles, and heavy motor vehicles to minimize bias.

Statistical methods

Descriptive statistics were used for demographic and work-related characteristics. Spearman’s correlation was used to assess relationships between pain, postural risks, and other variables. All analyses were performed using SPSS version 24 was manufactured by IBM. Named as IBM SPSS Software.

RESULTS

Out of 700 people approached, 438 were willing to participate in the study; 15 of them agreed to participate in the pilot study but did not for further analysis. Thus, the response rate was 60.42%. The median age of participants was 29 years (IQR: 9).

DISCUSSION

This cross-sectional study provides novel insights into the prevalence and risk factors of musculoskeletal disorders among vehicle repair mechanics in Mumbai, India. Tables 1 and 2 provide insights into the participant’s demographic profile and their job description. Our study not only sheds light on the current state of musculoskeletal health in this workforce but also raises important questions about the long-term implications of the observed postural risks and the potential for underreporting of symptoms.

Table 1.

Demographic characteristics of the participants (n=423)

Variable		Frequency (n)	Percentage (%)
Dominance	Right	406	96
	Left	17	4
Education	No formal training	17	4
	<10 grade	176	41.6
	<12 grade	190	44.9
	Graduate	40	9.4

Inference: Most participants (96%) were right-hand dominant, and 44.9% had education up to 12^th grade

Table 2.

Job profile of the participants (n=423)

Variable		Frequency (n)	Percentage (%)
Workplace Setup	Showrooms	87	20.6
	Garages	336	79.4
Working Hours	7-9	24	5.6
	10-12	211	50
	13-16	188	44.4
Working days/week	5	3	0.7
	6	122	28.9
	7	298	70.4
Working Experience (in years)	1-10	285	67.3
	11-20	113	26.8
	21-35	25	5.9
Types of vehicles serviced	Two wheelers	155	36.6
	Lightweight 4 wheelers	162	38.3
	Heavy weight 4 wheelers	106	25.1

Inference: Most individuals are working in a garage for 10 - 12 h per day every day. They have work experience of 1 - 10 years adopting the same position for < 1h

The biomechanical demands placed on vehicle repair mechanics during their work activities provide crucial insights into the development of musculoskeletal disorders. Our study found that lower back and knee pain as depicted in Table 3 were the most prevalent complaints among those reporting discomfort, which aligns with the biomechanical stresses inherent in common repair postures.

Table 3.

Pain profile of the participants (n=23)

Variables		Frequency (n)	Percentage (%)
Side	Right	23	100
Site	Neck	2	8.7
	Shoulder	2	8.7
	Upper Back	2	8.7
	Elbow	0	0
	Wrist/Hand	0	0
	Lower Back	6	26.1
	Hips/Thighs	2	8.7
	Knees	8	34.8
	Ankle/Feet	1	4.3
Intensity	At Rest	10	43.5
	At Activity	13	56.5

Inference: Among the 423 participants, 23 (5.4%) reported experiencing pain on the dominant side. The most common sites of pain were the knees (34.8%) and lower back (26.1%)

The stooping posture, frequently adopted by mechanics, places significant stress on the lumbar spine.[1] Trunk flexion, a frequent posture in vehicle repair, has been shown to increase compressive and shear forces on the lumbar spine. Punnett et al. (1991)[10] demonstrated that non-neutral trunk postures, particularly forward flexion exceeding 20 degrees, were associated with increased risk of low back disorders. Studies including Wami et al. (2019)[11] and Kerr et al. (2001)[12] have consistently demonstrated that prolonged trunk flexion significantly increases the risk of low back pain, with the risk escalating as both the degree and duration of flexion increase. This aligns with our observation of a positive correlation between REBA scores and lower back pain.

The prevalence of knee pain in our study population can be attributed to the frequent squatting and kneeling required in vehicle repair. These positions impose substantial stresses on the knee joint. Kajaks and Costigan (2015)[13] found that deep squatting postures can lead to tibiofemoral joint compression forces exceeding 7 times body weight. Wang et al. (2020)[14] found that occupational kneeling and squatting were associated with increased risk of knee osteoarthritis, particularly when combined with heavy lifting. This combination of postures and force application is common in vehicle repair tasks. This aligns with our finding of knee pain prevalence and highlights the biomechanical basis for potential knee disorders in this population.

Interestingly, despite these biomechanical risk factors, our study found a lower prevalence of reported pain (5.4%). One possible explanation lies in the concept of tissue adaptation. Solomonow (2012)[15] describes how cyclical loading of viscoelastic tissues, such as ligaments and intervertebral discs, can lead to adaptive responses that may temporarily mitigate pain. However, this adaptation may also mask cumulative microdamage, potentially leading to future disorders. Also, as explained by the findings of Januario et al. (2019),[16] perceived physical exertion does not always correlate with measured biomechanical load in occupational settings. They suggest that individual factors, including physical capacity and pain tolerance, may moderate the relationship between biomechanical load and perceived discomfort.

Furthermore, the young age and relatively short work experience of our sample may play a role. Kumar (2001)[17] proposed a differential fatigue theory, suggesting that younger individuals may have greater capacity to withstand mechanical stresses due to better tissue quality and repair mechanisms. This could explain the lower pain prevalence in our predominantly young sample. However, it is crucial to note that the absence of pain does not necessarily indicate the absence of harmful biomechanical stress. McGill (2015)[18] emphasizes that cumulative loading, even at levels below acute pain thresholds, can lead to tissue damage over time. This underscores the importance of ergonomic interventions even in the absence of high pain prevalence. Bovenzi et al. (1996)[19] found that age was a significant factor in the development of low back pain among professional drivers exposed to whole-body vibration and awkward postures. Long-term follow-up studies would be valuable to track how musculoskeletal health evolves over the career span of vehicle repair mechanics. These results, while encouraging, warrant careful interpretation within the context of the study population’s characteristics and the demands of their work.

The use of the REBA assessment in our study provides valuable understanding into the overall postural risks faced by vehicle repair mechanics as depicted in Table 4. However, recent research by Lim et al. (2020)[20] suggests that combining traditional observational methods like REBA with quantitative biomechanical analysis could provide a more comprehensive understanding of musculoskeletal risk. Du et al.[21] also found that prolonged periods of poor postures increase the risk of lumbar spine dysfunctions. The significant correlation between postural risk factors, particularly trunk posture, and overall ergonomic risk scores underscores the importance of addressing workplace ergonomics in this industry. Future studies could benefit from incorporating such multimodal assessments.

Table 4.

Relationship between pain and postural risks

Variables	P	r
Neck - Final REBA score	0.02	0.46
Trunk - Final REBA score	0.001	0.64
Legs - Final REBA score	0.02	0.46
Upper arm - Final REBA score	0.003	0.59
Lower arm - Final REBA score	0.39	0.18
Wrist - Final REBA score	0.26	0.24
Nordic lower back - Final REBA score	0.81	0.05
Nordic knee - Final REBA score	0.18	-0.28

Inference: REBA scores were significantly correlated with neck, trunk, legs, and upper arm posture. Lower back pain showed a positive correlation with REBA scores, although this was not statistically significant

To summarize, while our study provides important cognizance into the biomechanical risks faced by vehicle repair mechanics, it also highlights the need for more comprehensive, longitudinal research in this field. Future interventions should focus on reducing the biomechanical loads associated with trunk flexion and prolonged kneeling or squatting, potentially through ergonomic equipment (adjustable vehicle lifts, rolling mechanic seats, anti-fatigue mats) and redesign of workstations (angled mirrors to reduce neck strain, ergonomic handle designs, adequate lighting) or the introduction of assistive devices as well as training especially for on-field services.

Limitations

Potential limitations include response bias due to fear of job loss if reporting pain. The cross-sectional design prevents causal inferences. Sampling strategies limited representativeness of the population. Absence of female mechanics limits generalizability to all genders. Seasonal variations in workload were not accounted for during data collection. Single rater REBA assessments may introduce observer bias. The low prevalence of reported pain may be due to healthy worker effects, short work experience of the participants, or underreporting due to job security concerns. These findings, however, may be generalizable to young, relatively inexperienced vehicle repair mechanics in urban areas of India. Nevertheless, caution should be exercised in extrapolating to older or more experienced workers.

Moving forward, longitudinal studies would be beneficial to track the development of musculoskeletal disorders over time in this population. Additionally, implementing and evaluating ergonomic interventions, particularly those addressing trunk postures, could significantly contribute to preventing WMSDs among vehicle repair mechanics.

CONCLUSION

This cross-sectional study provides important revelation into the prevalence and risk factors of musculoskeletal disorders among vehicle repair mechanics in Mumbai, India. The documented prevalence of musculoskeletal pain was relatively low at 5.4%. Among symptomatic mechanics, lower back and knee discomfort predominated, aligning with the physical demands of automotive repair work. Statistical analysis confirmed significant correlations between trunk posture risks and overall ergonomic risk scores. This emphasizes the necessity for implementing specific ergonomic interventions such as adjustable vehicle lifts, ergonomic creepers, anti-fatigue mats in repair facilities.

In summary, while the immediate burden of musculoskeletal disorders appears lower than anticipated, the identified postural risks highlight the need for proactive ergonomic measures in the vehicle repair industry such as height-adjustable work platforms, proper tool design, scheduled rest breaks, and comprehensive ergonomic training programs. These evidence-based approaches could substantially improve occupational health outcomes for this vulnerable workforce.

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.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.