|Year : 2018 | Volume
| Issue : 3 | Page : 163-169
Work related musculoskeletal disorders and postural stress of the women cultivators engaged in uprooting job of rice cultivation
Amitava Pal1, Prakash C Dhara2
1 Department of Physiology, Panskura Banamali College, Purba Midnapore, West Bengal, India
2 Ergonomics and Sports Physiology Division, Department of Human Physiology with Community Health, Vidyasagar University, Midnapore, West Bengal, India
|Date of Web Publication||17-Dec-2018|
Prakash C Dhara
Ergonomics and Sports Physiology Division, Department of Human Physiology with Community Health, Vidyasagar University, Midnapore, West Bengal
Source of Support: None, Conflict of Interest: None
Aims: A large number of workers including women are involved in the informal sector in India. A majority of them are engaged in agricultural sectors. The agricultural workers have to perform their jobs by putting manual labor and are exposed to different occupational stresses. The present study was aimed to evaluate postural stress and prevalence of musculoskeletal disorder (MSD) of women cultivators engaged in uprooting job of rice cultivation. Settings and Design: This cross-sectional study was conducted on 166 women cultivators from different districts of West Bengal state, India. Materials and Methods: Prevalence and intensity of MSDs of the cultivators were evaluated by Nordic questionnaire and 10-point body part discomfort scale. Work rest pattern and postural pattern were studied by direct observation method. Postural stress was assessed by OVAKO Working Postures Analysis System (OWAS), Rapid Entire Body Assessment (REBA), Rapid Upper Limb Assessment (RULA), and Quick Exposure Checklist (QEC) methods and as well as by measuring center of gravity. Results and Conclusions: MSD was highly prevalent among the study participants. Lower back, hip, wrist, shoulder, and knee were highly affected. Higher prevalence of MSDs among the cultivators may be because of prolonged working hours and awkward postures. The women cultivators had to start their day before dawn to finish off their household chores such as cooking, cleaning, washing clothes and dishes, etc., before they moved off to the fields, which altogether impose them under additional stress. It may be suggested that ergonomic interventions such as modifying work-rest schedules, improving work postures, and introducing new design hand tools should be considered for improving work condition of the women cultivators.
Keywords: Postural stress, women cultivators, work related musculoskeletal disorder
|How to cite this article:|
Pal A, Dhara PC. Work related musculoskeletal disorders and postural stress of the women cultivators engaged in uprooting job of rice cultivation. Indian J Occup Environ Med 2018;22:163-9
|How to cite this URL:|
Pal A, Dhara PC. Work related musculoskeletal disorders and postural stress of the women cultivators engaged in uprooting job of rice cultivation. Indian J Occup Environ Med [serial online] 2018 [cited 2019 May 23];22:163-9. Available from: http://www.ijoem.com/text.asp?2018/22/3/163/247621
| Introduction|| |
India is an agriculture-based country. A large portion of Indian population lives in villages. They maintain their livelihood depending on agriculture. In West Bengal state, a large number of people are engaged in different types of agricultural jobs throughout the year. The Paddy (rice) is the main crop in this state. Both men and women workers are involved in this job and expend a great extent of their physiological cost for crop production. Among them women have great and important roles in different processes of crop production. Although investigations of men workers predominated, it is actually women who comprise the majority of subsistence farmers in developing countries., It is only relatively recently the role that woman play in the agriculture of developing countries has been recognized by agricultural experts and development agencies. It is important that women's roles and needs are not ignored.
The problems of agricultural task in developing countries were somewhat different from that of developed countries. In contrast to industrially developed countries, a large proportion of the population in developing countries is involved in agriculture. Although today Indian agriculture depends to a very large extent on manual labor, modernization has reached some parts of the subcontinent. The agricultural jobs are executed by adopting very difficult posture. Those postures may be the limiting factors, to some extent, for human capabilities. The agricultural workers have to face many job related problems during work.
For the rice (paddy) cultivation, several steps are followed, for example., preparation of land, sowing of seeds, uprooting of seedlings, transplantation, reaping, binding of straws, carrying of straw bundles, and threshing. Women workers are involved in most of the above said jobs. The preparation of land is done to make it suitable for the cultivation. It is first and most essential step for any type of cultivation. The paddy seeds are thrown on the prepared soil. After a few days; the seeds are germinated and grown into seedlings. For proper growth of seedlings, the farmers maintain optimum irrigation. After this, the seedlings become suitable for uprooting and transplantation. Workers use both their hands to grasp the base of shoot and pull them carefully. The seedlings become uprooted. After uprooting a number of seedlings, they wash the muddy root of the seedlings and tie them to form a bundle.
The workers adopt different postures during performing the above mentioned jobs. Sometimes, some of the postures that are adopted by the workers are very harmful. However, they are compelled to adopt those postures during work, even for a long time. Most of the tasks performed by the cultivators are monotonous, strenuous, physiologically demanding, and time-consuming., Because of adopting different postures during different agricultural jobs, they suffer in different problems or pain in their limbs and also in other body parts.,,, In the present investigation, uprooting operation has been considered. Usually, the women workers are performing this uprooting job in forward bending and squatting postures. These postures are known to create serious strain injuries. The prolonged forward bending posture causes high static muscular load particularly in the trunk region. The cumulative load on the musculoskeletal structures reflected in the form of high prevalence of discomfort and pain in neck, shoulder, and lower back and lower limb regions.,,
In the present investigation, the prevalence and features of work related musculoskeletal disorder (WRMSD) studied on the women agricultural workers who are engaged in uprooting job of rice cultivation. In addition, special emphasis has been given on the postural stress of women workers during performing their job.
| Methods and Materials|| |
Site and subjects
This cross-sectional study was conducted on 166 women cultivators having the age range of 18–50 years from Howrah, Purba Midnapore, and Paschim Midnapore districts of West Bengal state, India. Exclusion criteria for the participants included presence of any self reported chronic hypertension, heart disease, diabetes mellitus, respiratory diseases, or an accident affecting the musculoskeletal system. Pregnant and lactating women were also excluded from the study. The authors disqualified 28 participants because they were not eligible by these criteria. Seventeen women cultivators were not interested in participating in the present study, and nine women cultivators were excluded from the study because of incomplete or missing of data. Thus, a final total of 112 women cultivators participated in the present survey. The average age of the women cultivators was 34.85 ± 10.78 years. The average height and weight of the participants were 150.61 ± 6.5 cm and 46.22 ± 10.05 kg.
Prior to the data collection, the protocol was explained verbally to the participants to obtain their understanding and cooperation. Informed consent was obtained from the participants during field visits. Before commencement of the study, ethical approval and prior permission were obtained from the Institutional Ethics Committee, and the study was performed in accordance with the Helsinki declaration and with the ethical standards of the committee.
The prevalence of WRMSDs of the workers was evaluated by the modified Nordic questionnaire technique. The questionnaire emphasized their individual details, type of work, and the occurrence or frequency of pain felt in different parts of their body.
The intensity of different types of discomfort was evaluated by utilizing a 10-point body part discomfort scale. The scale consisted of marks from 1 to 10 and ranges from just noticeable discomfort to intolerable discomfort. A “0” in the scale meant no discomfort at all and “10” in the scale indicated intolerable discomfort. According to the degree of severity, the perceived rating of discomfort score of the 10-point scale were divided into three subgroups: Mild pain was defined as scale ≤4; moderate pain was defined as scale 4.1 to 6.9 and severe pain as scale ≥7. The mean value of scores (perceived rating of discomfort) of all segments was taken as the overall discomfort rating of the workers.
Evaluation of work rest pattern
The work-rest patterns of women cultivators were determined by directly observing their work and by taking interviews of the workers. The total work shift was divided into work cycle and rest cycle. The rest period was the sum of prescribed rest pause (rest for food break) and work related rest pause (rest taken by the worker for self requirement/or during working hour). The actual work time was calculated by subtracting the actual rest pause from total work time. It was recorded carefully from beginning to end of the work by direct observation method employing video-photography on the job. For this purpose, whole day task performance of the workers were recorded in DVD mode and the recorded DVD run in by media player (XingMPEG player, version 3.30) in the computer after setting a time. After a careful and repeated observation, the whole day work was evaluated and the duration of work time and different rest pauses of the workers were noted.
Determination of postural pattern
For evaluating the postural stresses, the postural pattern of the workers during performing their job was studied by direct observation method. The work posture of each participant was studied for whole working period. The postural change during performing the work was noted carefully and the time for adopting each posture was recorded. The observation was made by employing one participant-one day strategy.
Researcher proposed different methods for ergonomic assessment of work posture and quantification of ergonomic risk factors. Ergonomic assessment of work postures is one of the starting points to address the problem of WRMSD; as the risk of musculoskeletal injury associated with the posture. However, various techniques have been applied for postural analysis to identify the postural stress at work. Work postures were evaluated by OVAKO Working Postures Analysis System (OWAS) method. Although the OWAS method has a wide range of use, the results can be poor in detail. Therefore, Rapid Entire Body Assessment (REBA), Rapid Upper Limb Assessment (RULA), and Quick Exposure Checklist (QEC) methods were also applied for analysis work posture of the workers.
Center of gravity
The Center of Gravity (CG) of the workers was measured by means of segmental method. The CG of the workers was determined under rest (normal erect posture) and during different postures in uprooting job. The segmental CG and whole body CG of the workers were determined. The location of whole body CG was expressed in percent of body height taking ground as the reference.
Frequencies and percentages were used for categorical variables, and mean and standard deviation were used for continuous variables to summarize data. Differences were assessed by employing Student's t test and Chi-square test for continuous and categorical variables, respectively. Statistical analyses were performed using the statistical software IBM SPSS version 20. Statistical significance was set at P < 0.05.
| Results|| |
The results of the present study revealed that the prevalence of musculoskeletal disorders (MSDs) was very high among the workers [Table 1]. The lower back problem was highly prevalent (91.96%) among them, and it was followed by hip (91.07%), wrist (83.04%), upper back (81.25%), shoulder (81.25%), neck (73.21%) and knee (66.07%).
|Table 1: Frequency and percentage of cultivators reported musculoskeletal disorder during performing uprooting job|
Click here to view
The quantitative assessment of discomfort of the workers had also done by using a 10-point scale and the results showed that workers engaged in uprooting task of rice cultivation were suffering from different degrees of perceived exertion [Table 2]. It was revealed that severe degree of discomfort (≥7) was observed in lower back region and moderate degree of discomfort (4.1-6.9) was observed in thigh, buttock, middle back, upper back, arm, and shoulder regions among the workers. The overall discomfort rating of the workers was 4.35 (moderate pain).
|Table 2: The perceived rate of discomfort (mean±standard deviation) in different segments of the body of cultivators during performing uprooting job|
Click here to view
The work-rest pattern of women cultivator has been presented in [Table 3]. The workers generally started work by 7.00 am to 7.30 am and continued the work for about two or two and half an hours. After this, they took a food break for about 30–40 min. They resumed the work after this break and continued the work for about three to three and half an hours.
|Table 3: Mean±standard deviation of work time, rest time, and time (min) for adopting different postures of cultivators in uprooting job|
Click here to view
It was observed that the work time was about 86% of the total work shift and rest time was about 14%. The rest period of the workers was included the food break. Women cultivators were compelled to adopt in different awkward postures for prolonged period while performing uprooting job of rice cultivation [Figure 1]. The direct observation method was used for the analysis of posture and results are shown in [Table 3]. It was noted from the results that bending and squat sitting postures were the dominating postures in uprooting job. The workers were compelled to adopt forward bend posture more than 50% of the work-time and adopt squat sitting posture about 42% of the work-time.
|Figure 1: Postures adopted by the women cultivators during uprooting job ([a] Forward bending posture; and [b] Squat sitting posture)|
Click here to view
In the present study, different postures adopted by women cultivators while performing uprooting job was analyzed by four methods, for example., OWAS, RULA, REBA, and QEC [Table 4] and [Table 5]. It was already mentioned that the dominant postures adopted by the workers during uprooting job were forward bend and squat postures. From the results of postural assessment of uprooting job by OWAS method, it was found that the bending posture needed corrective measure immediately and squatting posture needed corrective measures in the near future. Similarly from the results of postural assessment by RULA and REBA methods, it was found that the bending posture has been categorized as very high risk and needed investigation and change immediately and squatting posture has been categorized as high risk and needed investigation further and change soon.
|Table 4: Scores and risk level of postural analysis of workers engaged in uprooting job of rice cultivation|
Click here to view
|Table 5: Postural analysis by quick exposure checklist method: Scores and risk level of workers engaged in uprooting job of rice cultivation|
Click here to view
The analyses of uprooting task using QEC indicated risk level to specific body parts including the back, shoulder/arm, wrist/hand, and neck. It was revealed that the risk level was high at shoulder/arm, wrist/hand, and neck regions during adopting both forward bending and squatting postures. The risk level at back was very high during adopting forward bending posture and high during adopting squatting posture. The result of posture analysis by QEC method indicated that the overall stress level of the workers was high for both forward bending and squatting postures.
The location of the CG of the workers engaged in uprooting task was evaluated and expressed as the percentage of body height [Table 6]. The location of CG under normal erect posture was taken as reference. The change of location of CG from the reference posture was regarded as the deviation of CG. The CG of the women workers during performing uprooting job was deviated from that of normal erect posture. During performing uprooting job in bending posture, the deviation of CG was 9.17 ± 1.57 and it was away from the base of the body. While performing the job in squat sitting posture, the location of the whole body CG shifted downwards, i.e., toward the base of the body.
|Table 6: Mean±standard deviation of percentage of center of gravity of women workers in different posture adopted during uprooting job|
Click here to view
| Discussion|| |
The WRMSDs was highly prevalent among the women cultivators engaged in uprooting job of rice cultivation. The segments of body that were highly affected were lower back, hip, wrist, upper back, shoulder, neck, and knee. In our previous study on women cultivators engaged in threshing job of rice cultivation, it was noted that WRMSD was highly prevalent in lower back, wrist, upper back, shoulder, and knee regions. Osborne et al. reported that the prevalence of MSDs among the farmers was greater than the non-farmer populations. WRMSDs top the list of occupational health morbidities' in developing countries due to lack of effective ergonomic interventions to reduce injuries and eliminate poor working conditions., Montakarn and Nuttika and Reddy et al. reported that MSDs is a major public health problem all over the developing countries and it is one of the leading causes for sickness absenteeism, disability, days of work lost, and hamper productivity at work. Yazdanirad et al. also stated that WRMSDs are the main cause of occupational injury and disability in industrialized countries and affecting not only individuals but also organizations and society. MSDs are the common occupational hazards among the agricultural workers. The higher prevalence of MSDs among the women cultivators might be related to the prolonged work in awkward postures (forward bend posture and squatting posture). Present study revealed that workers had to perform the task for a prolonged period of time with lesser period of rest. Researchers pointed out that higher incidence of MSDs may be related to the postural pattern at work, repetitive movements, and longer duration of exposure in awkward posture.,,, Madhwani and Nag reported that awkward and static postures cause musculoskeletal stress on different body regions and are a major factor in the development of WRMSDs. The women cultivators had to start their day before dawn to finish off their household chores such as cooking, cleaning, washing clothes and dishes, etc., before they moved off to the fields, which altogether impose them under additional stress.
The back pain was highly prevalent among the study participants. The workers suffered from such problems might be because of adopting forward bending and squat sitting postures for long time. In uprooting job, they were compelled to twist their trunk frequently. The spinal rotation may cause chronic strain as when the workers twist their waist during work. In a study by Osborne et al. reported that the farmers were suffering from WRMSD at different body segments particularly lower back region followed by upper and then lower extremity. The lower back pain has been regarded as double burden on the quality of life and on health expenditure. The main reason for frequent backaches was a pathological degeneration of the discs of spinal column. Awaked postures such as forward bending and squatting postures wore out the discs and induced hazards on the supporting system of spine and trunk. The pressure inside the discs was considerably increased when the trunk was bent forward compared with standing in an upright position. The intradiscal pressure was also higher in the sitting than in the standing posture. This was certainly due to the turning mechanism of the hips in the sitting position, which produced a kyphosis in the lumber region of the spine. A great increase in intradiscal pressure must be considered as an unnecessary load and strain on the discs. It was generally accepted that prolonged heavy manual work might encourage the development of degenerative changes in the joints.
MSD at upper extremity was also highly prevalent among the workers. Higher prevalence of MSD at shoulder might be due to frequent movement and abduction of shoulder during uprooting job caused static load imposes in the shoulder. The MSD at neck was also high. Repetitively movement of shoulder and static load on the trapezius muscles may be cause of the musculoskeletal illness in the shoulder and neck., The trapezius is the main lifter of the shoulder girdle and is important in stabilization of the scapula, which is necessary when making precision movement of the arm. The load on the trapezius may, therefore, be considered a reasonable indicator of load on the shoulder and neck region. In addition to that the workers reported pain in their wrist. There were dorsiflexion, ventriflexion, and lateral movements of wrist joint during uprooting operation that impose static load on it. Repetitive exertions and excessive movements of the wrist increase the resultant reaction force on the tendons passing through the carpal tunnel. The resultant reaction force could degenerate and inflame the tendons, thereby causing tenosynacitis, or compress the median nerve between the carpal ligament and tendons, which could cause carpal tunnel syndrome.
The worker reported MSDs in different parts of lower limbs during performing uprooting job. The most affected part of the lower limb was thigh and knee. In uprooting job, the movement of the lower limb was very less. Therefore, a great amount of static load was imposed on the upper leg muscles during working under forward bending and squat sitting postures. This might be the possible reason for the occurrence of MSDs at thigh. Pal and Dhara reported that forward bending and squatting postures in the workplace are significant contributors for MSD at knee and thigh.
Human body has a CG and in any movement of body the position of CG plays an important role. In the present study, the location of CG of the women workers in normal erect posture was around 60% of body height. In our previous study among the women cultivators, the CG in normal erect posture was also around 60% of body height. The present study showed that the working CG at different postures (forward bend and squatting postures) was deviated during performing uprooting job. In squatting posture, the location of CG shifted downwards, i.e., toward the base of the body. When the CG was shifted toward the base of the body, it became more stable than that in erect posture. However, the results of posture analysis by different methods revealed that squatting was awkward posture, which leads to strain in different joints and muscles of the lower limbs. The CG indicates the stability of the body. However, work in squatting posture leads to static postural load on the lower limbs caused MSD at those areas. The location of the CG shifted away from the base of body during performing the job in forward bend posture. As the CG shifted upward, biomechanical stress was imposed on the body that might be the cause of MSD. Das and Ganguli, and Sen and Ray reported that the shift in CG imposed maximum postural load in forward bend postures when considered from the viewpoint of biomechanical stress.
| Conclusions|| |
The present study concluded that the higher prevalence of WRMSDs among the women cultivators may be because of prolonged working hours and awkward postures. The women cultivators had to start their day before dawn to finish off their household chores such as cooking, cleaning, washing clothes and dishes, etc., before they moved off to the fields, which altogether impose them under additional stress. It may be suggested that ergonomic interventions such as modifying work-rest schedules, improving work postures, and introducing new design hand tools should be taken for improving work condition and postures of the women cultivators to reduce their work stress. Awareness and training programs about personal protective devices, correct work posture, and proper work methods among the workers may be another solution of the problem.
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.
The authors gratefully acknowledge the financial assistance provided by the DST (RVPSP), New Delhi, which could make it possible to complete the present study. All the authors wish to express their gratitude to the subjects who volunteered for this study.
Financial support and sponsorship
DST (RVPSP), New Delhi.
Conflicts of interest
There are no conflicts of interest.
| References|| |
Goswami S, Pal A, Dhara PC. Evaluation of work related musculoskeletal disorder and postural stress among female cultivators engaged in post harvesting tasks. Indian J Biol Sci 2012;18:16-25.
Pal A, De S, Sengupta P, Maity P, Dhara PC. Evaluation of work related musculoskeletal disorder and postural stress among female potato cultivators in West Bengal, India. Ergonomice SA 2015;27:46-64.
Pal A, De S, Sengupta P, Maity P, Mahata H, Shaikh S, et al.
Physiological strain among women potato cultivators in West Bengal, India. J Hum Ergol (Tokyo) 2015;44:61-74.
Gangopadhyay S, Das B, Das T, Ghoshal G. An ergonomic study on posture-related discomfort among preadolescent agricultural workers of West Bengal, India. Int J Occup Saf Ergon 2005;11:315-22.
Das B, Gangopadhyay S. Prevalence of musculoskeletal disorders and physiological stress among adult, male potato cultivators of West Bengal, India. Asia Pac J Public Health 2015;27:NP1669-82.
Pal A, De S, Sengupta P, Maity P, Dhara PC. Ergonomic evaluation of work related musculoskeletal disorders and postural stress among male potato cultivators of West Bengal, India. Int J Occup Saf Health 2014;4:5-14.
Pal A, Dhara PC. Evaluation of work-related musculoskeletal disorders and postural stress of female “Jari” workers. Indian J Occup Environ Med 2017;21:132-7.
] [Full text]
Kuorinka I, Jonsson B, Kilbom A, Vinterberg H, Biering-Sørensen F, Andersson G, et al.
Standardised nordic questionnaires for the analysis of musculoskeletal symptoms. Appl Ergon 1987;18:233-7.
Reynolds JL, Drury CG, Broderick RL. A field methodology for the control of musculoskeletal injuries. Appl Ergon 1994;25:3-16.
Dutta S, Dhara PC. Evaluation of different sitting postures of rural primary school boys in the classroom. J Ergon 2012;2:1-7.
Wilson JR, Corlette EN. Evaluation of Human Work – A Practical Ergonomics Methodology. London: Taylor and Francis; 1985.
Kee D, Karwowski W. A comparison of three observational techniques for assessing postural loads in industry. Int J Occup Saf Ergon 2007;13:3-14.
Heinsalmi P. Method to measure working posture loads at working sitess (OWAS). In: Corlett EN, Wilson JR, Manenica I, editor. The Ergonomics of Working Postures. London: Taylor and Francis; 1986. p. 100-4.
Hignett S, McAtamney L. Rapid entire body assessment (REBA). Appl Ergon 2000;31:201-5.
McAtamney L, Nigel Corlett E. RULA: A survey method for the investigation of work-related upper limb disorders. Appl Ergon 1993;24:91-9.
Li G, Buckle P. A Practical Method for the Assessment of Work-Related Musculoskeletal Risks – Quick Exposure Check (QEC), Human-System Interaction: The Sky's No Limit. Proceedings of the Human Factors and Ergonomics Society 42nd
Annual Meeting. Vol. 2. 1998. p. 1351-5.
Page RL. The Physics of Human Movement. Leeds: Arnold Wheaton; 1978. p. 33-44.
Osborne A, Blake C, Fullen BM, Meredith D, Phelan J, McNamara J, et al.
Prevalence of musculoskeletal disorders among farmers: A systematic review. Am J Ind Med 2012;55:143-58.
Yazdanirad S, Khoshakhlagh AH, Habibi E, Zare A, Zeinodini M, Dehghani F, et al.
Comparing the effectiveness of three ergonomic risk assessment methods-RULA, LUBA, and NERPA-to predict the upper extremity musculoskeletal disorders. Indian J Occup Environ Med 2018;22:17-21.
] [Full text]
Madhwani KP, Nag PK. Web-based KAP intervention on office ergonomics: A Unique technique for prevention of musculoskeletal discomfort in global corporate offices. Indian J Occup Environ Med 2017;21:18-22.
] [Full text]
Montakarn C, Nuttika N. Physical activity levels and prevalence of low back pain in Thai call-center operators. Indian J Occup Environ Med 2016;20:125-8.
] [Full text]
Reddy GM, Nisha B, Prabhushankar TG, Vishwambhar V. Musculoskeletal morbidity among construction workers: A cross-sectional community-based study. Indian J Occup Environ Med 2016;20:144-9.
] [Full text]
Caicoya M, Delclos GL. Work demands and musculoskeletal disorders from the Spanish national survey. Occup Med (Lond) 2010;60:447-50.
da Costa BR, Vieira ER. Risk factors for work-related musculoskeletal disorders: A systematic review of recent longitudinal studies. Am J Ind Med 2010;53:285-323.
Roffey DM, Wai EK, Bishop P, Kwon BK, Dagenais S. Causal assessment of awkward occupational postures and low back pain: Results of a systematic review. Spine J 2010;10:89-99.
Jadhav AV. Comparative cross-sectional study for understanding the burden of low back pain among public bus transport drivers. Indian J Occup Environ Med 2016;20:26-30.
] [Full text]
Girish N, Ramachandra K, Arun GM, Asha K. Prevalence of musculoskeletal disorders among cashew factory workers. Arch Environ Occup Health 2012;67:37-42.
Hayes M, Cockrell D, Smith DR. A systematic review of musculoskeletal disorders among dental professionals. Int J Dent Hyg 2009;7:159-65.
Das RN, Ganguli S. Mass of center of gravity of human body and body segments. J Instit Eng 1982;62:67-72.
Ray GG, Sen RN. Determination of whole body centre of gravity in Indians. J Hum Ergol (Tokyo) 1983;12:3-14.
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]