Health Science Journal

Keywords

Upper extremity; Agricultural worker; Farmers; Ergonomics; Risk factors; Upper limb; Musculoskeletal system

Introduction

Ergonomics renewed approaches suggest the application of more practicality in identification of possible ergonomic problems, before the appearance of Musculoskeletal Disorders (MSD's). Risks are presented by using of muscles when exerting a certain level of strength making any work, since the greater the demand, the greater the effort [1]. This effort can cause muscle injury, whether by repeated force, sustained force, or, even an uncomfortable posture [2]. In 2004, World Health Organization (WHO) pointed out that exists a causal link between MSD's and physical tasks during work activity, because of the muscles may require excessive effort to maintain the posture or support repetitive muscle charges during long periods of time such is likely to produce muscular fatigue [3]. Being exposed to these risk factors, labelled as MSD's, increases the likelihood of worker injuries [4]. Data from 5th European Survey of Working Conditions, Eurofound - 2012, frequently reveal that perceived risk to present MSD in workers, is mainly due to two factors: repetitive movements of upper limbs in more than a quarter of their working day: 63%, and, for adopting forced and/or tiresome postures: 46%, showing a prevalence increase since 2005 [5]. Worldwide high productivity rates force rural work to be more competitive, promoting the reduction in operating costs and yields increasing [6]. Saving in operation costs depends on types of crop, since the most of them are harvested manually, either by environmental conditions, the natural terrain where they are cultivated or the type of fruit to be harvested, since these are traditionally separated from the tree by hand or with using handcutting tools. Those efficiency requirements make of process an activity that generates problems in worker's health [7,8]. Level of perception in agriculture workers shows discomfort or pain in 62.6% [9], either performing work by standee, on stairs, flexing lower limbs, or frequent uncomfortable postures during long periods of time [10].

Several models of kinematic valuation for upper limbs, require of choosing the model through body multiple kinematic optimization, and depends directly on limitations and degrees of freedom for analysis [10,11]. Into literary collections exists a great availability of kinematic models for upper limbs; e.g. for shoulder modeling, were found that the number of published articles, since 1990 to 2009, can reach 100 [12].

This set of applications for motion analysis can refer to medical evaluation, monitoring or activity recognition. These applications are supported by specialized high-precision systems, mobile systems or wireless sensor networks widely used in health areas, entertainment or leisure games [13].

In the same way into biomechanics allowing the measuring of posture; nowadays, electronic devices have great level of acceptance. Physical media such as sensors record angles, speeds and/or distances, which thanks to their accuracy and interconnection, can obtain automatically data from different variables, and even have the possibility of continuous monitoring [14,15].

In accordance with U.S. Department of Labor's Occupational Safety and Health Administration (OSHA), evaluation is necessary not only for recognition of risk factors, but also to measure periodically the effectiveness of ergonomic process, and so determine an effective compliance with implemented procedure [15].

Based on the above, the purpose of this review is identify available evidence in electronic databases, its quality, and detailed description of used methods in order to establish a basis to design direct measurement tools that bring support to an early identification of symptoms or incidence of MSD's in agricultural workers whom perform manual labours.

Literature and Method

Reviewing of literature by using and combining the keywords: agricultural worker (MeSH), farmers (MeSH), ergonomics (MeSH), risk factors (MeSH), musculoskeletal system (DeSH), upper limb (DeSH), upper extremity (MeSH), the latter used as an arm synonym. This set of words were chosen after an initial experimental search in order to understand the citated publications behaviour in databases and gray literature. As a search strategy for the articles, were chosen five databases catalogued for contents and information quality: Web of Science, Escopus, ScienceDirect, ESBCO - PubMed and IEEE. At the time, it was established a publication date restriction between the years of 2013 and 2018.

The following factors were selected as the inclusion criteria: original articles or comparative studies such as controlled trials, study subjects belonging to agricultural sector and whose results show method effectiveness and symptoms or discomfort presented by members of study group. Publication date of articles were stated since July 2013 to July 2018, texts written in English, classified by type and conditioned to be a full access document. About the exclusion criteria: at first it was excluded documents produced by publishing houses, legal entities presentations as well as review articles. With the same criterion, it was excluded investigations with directed populations to other economic activities such as agro-industrial workers whom use traction or locomotion tools machines.

As shown in the systematic review of Menegaz AM, Silva AER et al [16], a checklist was used to evaluate the methodological quality of studies [17] and encountered difficulties were adjusted due to comprehension in some elements definition. After this reviewing were selected 37, documents taking into account a basic documentary structure with 10 questions, internal and external validity with 8 questions, omitting those directed to attempt to blind study subjects or pretend to blind whom measure main results, all this considering logistical difficulties in the studies. Selection biases were assessed by choosing 6 questions and a statistical power value to detect the effect. Through the instrument adjusting, score was stated between 0 and 26, the studies were ranked in accordance with the quality of evidence on an established scale as: Excellent (24-26), Good (20 to 23), Reasonable (15 to 19) or Limited (14-0). These set of criteria were similar to those adjusted in the systematic review made by Cascaes AM, Bielemann RM et al [18].

Results

In Initial search were reported a total of 1508 articles (Table 1), after depuration by duplicity only left 1312. Made the reading both title and summary, another 1263 were excluded, so the set of selected articles for an entirely reading was reduced to 49. In agreement with selected criteria, 6 articles which did not include in their results Musculoskeletal Disorders (SMD's) [19-23], were excluded. Another article was left out because of being a work in progress [24], another one was rejected due to its analysis took place after an invasive procedure [25], an additional one because of evaluation was made with farmers whom perform tasks without direct contact with nature [26], one of them due to its method involves clinical analysis (bone mineral density) [27], another one with risk assessment design based on tests of lung function and heart rate [28], one due to the approaching of analysis which was presented with a malformation in lower limbs (misalignment in knees) [29] and a last work because it was used a questionnaire with characteristics of World Health Organization (WHO) combined with qualities of complementary alternative medicine (CAM) [30]. At the end, only 37 articles met all established criteria. Selection process is shown in Figure 1.

Figure 1: Selection of articles for review.

Table 1 Articles identified in bibliographic databases.

According to Delphi consensus, peers who addressed the selection of articles (Ruíz A and Jaramillo S), suggested to keep articles directed to use an ergonomic method, either by observation, analysis with techniques of direct measurement or ergonomic evaluations methods with self-reported questionnaires. Intervention made with each one of selected articles was recorded in a table under criteria of PRISMA Declaration and classified according with approaches of physical ergonomics [31,32]. Table 2 shows all of the 37 selected articles, classified in groups, according to the evaluation method included in methodological design.

Table 2 Ergonomic evaluation tools.

It was found a little quantity of articles about upper limbs ergonomic evaluation in farmers. Those ones identified refer to musculoskeletal pain in at least one part of body during the last year, produced by activities or tasks that are repeated regularly [33] or caused by unsafe postures adopted [8]. Most of MSD's in one or more regions of the body are associated with age [25,34,35], as well as common causes attributed to lumbar problems produced due to lifting, pulling, or pushing heavy loads [36]. In this point it is important to highlight that there are a few standardized tools available to assess safety and health in manual agricultural operations [37]. Near to 45.9% [17] of related articles in this review used the indirect method known as Nordic Musculoskeletal Questionnaire (NMQ), commonly used in occupational health and agriculture activities, among other uses [38]. Within these 17 articles, 4 used it only, 5 in combination with an observation method and 8 in combination with another questionnaire.

The selected articles are indexed in 24 different journals; in order of repetition: 4 in Annals of Agricultural and Environmental Medicine, 3 in Work, and 3 in Journal of Agromedicine, among others. 27% point their objective to detect prevalence and 32% identify the exposure to risk factors, as seen in Table 3.

Table 3 Identification of Articles and general characteristics.

In Asia were made 48% [18] of investigation works: 5 in India [34,39-42], 3 in Thailand [43-45], 4 in Malaysia [7,8,46,47], 3 in South Korea [48-50], 2 in Indonesia [51,52], and 1 in Sri Lanka [53]. 72.9% of articles are based on cross-sectional studies; 18 of them used a population range between 100 to 900 farmers and only in one study were involved children with a sample of 120 participants [39]. In the same way, also in was identified a cohort study with a population of 1013 subjects [49], as well as two cross-sectional studies, one with 2469 subjects [54] and other with 2595 people [33]. Within the review, a cross-sectional study using 15980 people data from the 2012 Korean Farmers Occupational Diseases and Injuries Survey (KFODIS) [50] was also identified. Only one study used the observational method (RULA) to redesign tools [51], and the others were oriented to prevalence of MSD's.

The articles quality evaluation recorded in Table 4 shows an average of 18.95 (PD=3.92), although a minimum value of 8 points was obtained in an article [40], it was possible to confirm a high value in another article of excellent quality with 25 points [41], followed by 7 articles of good quality with 23 points [33,35,36,42,50,55,56]. The greatest methodological difficulties encountered were related to external validity and confusion, whether during planning study, during sampling process, during data collection, or during analysis and interpretation stage.

Table 4 Quality of the articles, according to the criteria of Downs and Black [17].

Discussion

As a result of this review was possible determine that Nordic Questionnaire is the most widely used tool in these cases. Within its structure incorporates several questions addressed to detect effects on health, symptoms of discomfort or pain for detection of MSD's and allows a comparison with different regions of the body [57]. Perception of discomfort or pain risk is revealed in 5 papers with different values in effect magnitude: the first one refers to high physical stress associated with farm work produced by lifting or energetic movements, logistic regression model refers to significance in worker activity with values for p=0.021 and OR=3.74 [58]. The second showed that 31% of vegetable farmers report physical problems due to manual harvesting, within of them 91% report back disorders followed by arms and hands problems [59]. In the third article it was determined the prevalence of total MSD's during the last 12 months in any part of the body, showing a value of 93%. When prevalence values were segregated for each part of body, the highest one was found in lower back with 58% followed by knee 45.5%, shoulder 32.9%, and neck 32.9% as the most representative results [60]. The fourth article showed the most significant prevalence related to time spent on biomechanical tasks, over shoulders p=0.024 or lifting objects under lower back p=0.001, knee p=0.019 [33]. And the last article showed a comparison of pain perceived by experienced and inexperienced farmers. In experienced farmers forearm p=0.0109, hand p=0.0026 and leg p=0.0015; and in inexperienced farmers neck p=0.0001 and lower back p=0.0001 [45].

Nevertheless, in general, Nordic Musculoskeletal Questionnaire (NMQ) [61] is used as a previously pre-validated version [62,63] in combination with another tools and adjusted modifications to the specific objective of each research. In a total of 11 articles which demonstrated this condition, four were combined with other questionnaires, one [64] of them with job satisfaction, another [44] with the Global Physical Activity Questionnaire (GPAQ), an additional one with a stress scale and the Peradeniya depression scale designed in Sri Lanka based on cultural traits [53]. One of the most interesting articles [36] showed a combination of questions with another from the National Farmers' Survey in Ireland (NFS), the Survey for Lifestyle, Attitudes and Nutrition in Ireland (SLAN) and the NMQ, used to find causes and consequences of low-back pain (LBP) in farmers; the article was evaluated with 23 points and ranked in the scale as Good Quality. In the statistical analyses, latter article also showed that probability of LBP in farmers operating larger farms was significantly higher (OR=1.71, 95% CI: 1.08-2.72) than in small farms, but it was found no statistical significance among those whom operate medium farms compared to farmers operating small farms.

The set of works mentioned above show that using of NMQ tool is adjusted to identify symptoms or musculoskeletal pathologies and allows a MSD's comparison in different regions of the body in order to develop epidemiological studies for large populations [57]. Even, it has been used in a long variety of fields of knowledge, as seen with some documents showing 68% of them were directed to activities of attending human health and social assistance [38].

Other results showed the use of observation methods such us RULA, REBA, OWAS, and OCRA. In general, these methods were accompanied by evaluation instruments to capture the respondent perception, inherently subjective models. Among this type of works were those by Putri [51] where only was used RULA method for tools redesigning based on user ergonomics. Another by Deros [8] where REBA was used to TMEs exposition detection in agricultural workers. The OWAS method was used by Velásquez S, Valderrama D et al [65], focused on the study of work postures and postural risk in rubber plantation workers. The OWAS method was used in combination, NMQ and RULA by Thetkathuek [43], to assess posture risk in the work of migrant farmers in Thailand, and also in work by JAIN [34] to determine the prevalence of MSDs in farmers whom harvest manually. Combination of NMQ, REBA and OWAS methods was used by Das [39] to identify posture-related discomfort in child farm workers; statistical analysis showed that prevalence of discomfort was statistically significant in the group of exposed workers and greater than such in the control group for different body parts: neck (OR=9.3; p=0.000), shoulder (OR=12.5; p=0.000), elbow (OR=9.6; p=0.000), wrist (OR=8.4; p=0.000), hand (OR=9.3; p=0.000), upper back (OR=9.6; p=0.000), lower back (OR=72.1; p=0.000) and knee (OR=6.5; p=0.000).

In fact, in only two works were used direct measurement methods which demonstrates the limited use of motion capture technologies or postural angles. In first document by Tang [66], two interventions were evaluated to reduce risk of lumbar disorders produced by loads lifting through designing new tools, where each one of participants was equipped with a threedimensional spinal electrogoniometer while lifting, transporting and throwing buckets of water, using both those two proposed methods and the one accustomed. Clearly this type of studies direct the efforts to prevent MSDs in agricultural activities and show that electronic aids allow a direct, exact and in real time evaluation, which contributes in this case to design ergonomic and suitable elements. In the second work [67], ergonomic evaluation tools were combined in order to determine musculoskeletal load in farmers’ manual tasks. Upper limb tension occurred during manual handling of loads is measured based on the work effort index study, through an electromyography device (EMG), this way percentage of maximum contraction is measured. At the end, the obtained data were analyzed, both time-distance parameters and kinetic values so as to determine the correct corporal posture of farmers during muscular work.

In this point is particularly important to highlight the use of direct measurements which can be useful in developing of ergonomic interventions, in manual tools redesign, workplace adjustments, training guidelines on physical behaviour and ergonomic assessment methods. These objective interventions related to agricultural ergonomics must take into account the environment, activities and specific products [68]. Electronic elements of easy handling and access such as video capture or inertial sensors [69], can be directed to state a permanent control in real time to prevent MSD's in work activities with suspicion occurrence or presence of body discomfort/pain. This type of monitoring can contribute to achieve an improvement in levels of quality life of workers and mitigate public health overdemand which increases social security expenses.

Conclusion

Results showed that the most of evaluation techniques used are indirect: realized by self-administered questionnaires (SAQ) or self-reporting, this is an evidence of little ergonomic analysis in farmers doing manual work; most of the studies selected were catalogued as good or reasonable quality. This systematic review highlights the needing of adjusting tools in order to identify and evaluate potentially dangerous tasks by their movements and/or postures in real time.

Funding

This article was supported by the VCTI of University project number 2017227.

Conflicts of Interest

None of the authors declares conflicts of interest.

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