Original Research
Occupational Ergonomics & Risk Assessment

Validity Test for Simple Ergonomics Risk Assessment (SERA) Method

Background

Occupational ergonomics is a critical discipline within public health, particularly in industries where workers are exposed to repetitive physical tasks, awkward postures, and manual handling of heavy loads. In Malaysia, the oil palm industry is one of the nation’s largest agricultural sectors, employing hundreds of thousands of workers in physically demanding roles including harvesting, collecting, and transporting fresh fruit bunches (FFB). These workers face significant ergonomic risk factors that contribute to work-related musculoskeletal disorders (WMSDs).

Existing ergonomic risk assessment methods, while valuable, have been identified as having limitations in practical field applications. Tools such as the Rapid Upper Limb Assessment (RULA), Rapid Entire Body Assessment (REBA), and Quick Exposure Check (QEC) are widely used internationally but may be complex to administer in field settings, particularly for non-specialist assessors. Moreover, some existing tools lack comprehensive assessment of all relevant body regions or may not be sufficiently intuitive for use by health and safety officers without extensive ergonomics training.

Recognising these limitations, Sukadarin and colleagues developed the Simple Ergonomics Risk Assessment (SERA) method — a pen-and-paper-based assessment tool designed to be practical, comprehensive, and accessible for use in diverse workplace settings. This study describes the validity testing of the SERA method, a crucial step in establishing its scientific credibility before wider implementation.

Methodology for Validity Testing

The researchers conducted two types of validity testing: content validity and criterion validity. Content validity assesses whether an instrument adequately covers the construct it intends to measure, as judged by experts in the field. Criterion validity evaluates whether the results of a new instrument correspond meaningfully to those of an established measurement.

For content validity, six ergonomics experts were recruited to systematically review the SERA method. These experts evaluated the comprehensiveness of body regions assessed, the clarity of posture illustrations, the logic of the scoring system, and the overall usability of the assessment form. The experts provided iterative feedback, which was used to refine the method before criterion validity testing.

For criterion validity, data were collected from oil palm workers during harvesting activities. The researchers administered the Nordic Musculoskeletal Questionnaire (NMQ), a well-established and validated instrument for assessing self-reported musculoskeletal complaints. Simultaneously, SERA assessments were conducted on the same workers during the same activities. The correspondence between NMQ-reported complaints and SERA-identified risk scores was then evaluated using Chi-square tests.

Content Validity Findings

The expert review process identified several issues with the initial SERA prototype that required modification. These included confusing posture illustrations that made it difficult to distinguish between risk levels, inadequate illustration of leg postures, a scoring system placement that was unintuitive, and colour codes that were not clearly differentiated. Following expert feedback, the method was substantially revised, with clearer illustrations, improved scoring layout, and more distinct visual indicators of risk levels.

The iterative expert review process is consistent with best practices in measurement development and reflects the thoroughness of the researchers’ approach. By addressing each concern raised by the experts, the final version of SERA represented a substantially improved instrument compared to the original prototype.

Criterion Validity Findings

The criterion validity testing focused on two primary oil palm harvesting activities: fresh fruit bunch (FFB) harvesting and loose fruits collection. FFB harvesting involves using a chisel or sickle on a long pole to cut heavy fruit bunches from tall palms — an activity requiring sustained overhead reaching, trunk extension, and forceful exertion. Loose fruits collection involves bending, stooping, and manual handling to gather individual fruits that have fallen to the ground.

The results demonstrated significant associations between SERA risk scores and NMQ-reported complaints for most body regions assessed. For FFB harvesting, significant Chi-square associations were found for neck posture, hip, right and left shoulders, right and left wrists, and the right hand. For loose fruits collection, similar significant associations were identified for neck, hip, shoulders, right wrist, right arm, and left hand.

The notable exception was the leg posture assessment, which showed no significant association between SERA scores and NMQ complaints for either activity. This finding represents both an honest limitation and an opportunity for future refinement of the method.

Implications for Workplace Ergonomics Practice

The validation of SERA addresses an important gap in occupational health practice in Malaysia and similar developing economies with large agricultural workforces. Existing gold-standard ergonomic assessment methods, while scientifically robust, often require specialised training and may not be practical for routine use in field settings. SERA offers a simpler alternative that, while not replacing comprehensive assessment tools, can serve as an effective screening instrument to identify workers and tasks at elevated ergonomic risk.

In the context of Malaysia’s oil palm industry, where musculoskeletal disorders are estimated to affect 86–99% of manual harvesting workers based on various studies, tools that facilitate early identification of ergonomic risk factors have significant potential to reduce the burden of occupational injury and disability. The SERA method’s pen-and-paper format makes it accessible for health and safety officers, plantation supervisors, and occupational health practitioners who may not have formal ergonomics training.

The development and validation of SERA also represents an important contribution to the global literature on ergonomic assessment methods developed specifically for agricultural settings in tropical developing countries. Most existing tools were developed and validated in industrial or office settings in high-income countries, and their applicability to agricultural work in different climatic and cultural contexts may be limited.

← Back to MJPHM Homepage