I.E. and Ergonomics, need to merge - Articolo di Gabriele Caragnano

I disordini muscoloscheletrici derivano da un'interazione complessa di fattori che si accumulano nel tempo, ad esempio compiere movimenti ripetitivi più volte durante la giornata o per lugno tempo. Per questo motivo, tali disturbi sono riconducibili ad attività lavorative che richiedono importanti sforzi fisici, in cui non è raro incorrere nel rischio di sovraccarico biomeccanico. Cosa comportano, a livello fisico, questi disturbi? Come si possono curare e, soprattutto, prevenire? Esiste una vera e propria legislazione in materia di ergonomia? 

Gabriele Caragnano, Partner PwC e Direttore Tecnico di Fondazione Ergo, riporta la sua diretta esperienza.

Work-related musculoskeletal disorders arise from a complex interaction of events that may accumulate over time. In contrast to the acute trauma model (injuries refer to those arising from a single identifiable event), the cumulative trauma model assumes injury may result from the accumulated effect of transient external loads that may, in isolation, be insufficient to exceed internal tolerances of tissues. It is when this loading accumulates by repeated exposures, or exposures of sufficiently long duration, that the internal tolerances of tissues are eventually exceeded. The cumulative trauma model therefore explains why many musculoskeletal disorders are associated with work, because individuals often repeat actions (often many thousands of times) throughout the workday, or spend long periods of time (as much as eight hours or more daily) performing work activities in many occupations. Internal mechanical tolerance represents the ability of a structure to withstand loading. It is clearly multidimensional and is not considered a threshold but rather the capacity of tissues to prolong mechanical strain or fatigue. Internal tissue tolerances may themselves become lowered through repetitive or sustained loading. 

External loads are produced in the physical work environment. These loads are transmitted through the biomechanics of the limbs and body to create internal loads on tissues and anatomical structures. Biomechanical factors include body position, exertions, forces, and motions. External loading also includes environmental factors whereby thermal or vibrational energy is transmitted to the body. Biomechanical loading is further affected by individual factors, such as anthropometry, strength, agility, dexterity, and other factors mediating the transmission of external loads to internal loads on anatomical structures of the body.

External loads are physical quantities that can be directly measured using various methodologies. External kinetic measurements, for example, include physical properties of the exertions (forces actually applied or created) that individuals make. These measurements have the most direct correspondence to internal loads because they are physically and biomechanically related to specific anatomical structures of the body. When external measurements cannot be obtained, quantities that describe the physical characteristics of the work are often used as indirect measures. These include (a) the loads handled, (b) the forces that must be overcome in performing a task, (c) the geometric aspects of the workplace that govern posture, (d) the characteristics of the equipment used, and (e) the environmental stressors (e.g., vibration and cold) produced by the workplace conditions or the objects handled. Alternatively, less directly correlated aspects of the work, such as production and time standards, classifications of tasks performed, and incentive systems, are sometimes used as surrogate measures to quantify the relationship between work and physical stress.

The literature contains numerous methodologies for measuring physical stress in manual work. Studies from different disciplines and research groups have concentrated on diverse external factors, workplaces, and jobs. Factors most often cited include forceful exertions, repetitive motions, sustained postures, strong vibration, and cold temperatures. 

The ISO 11228 series, ISO 11226 and ISO TR 12295 establish ergonomic recommendations for different manual handling tasks, repetitive movements and working postures. All their parts apply to occupational and non-occupational activities. The standards will provide information for designers, employers, employees and others involved in work, job and product design, such as occupational health and safety professionals.

· ISO 11228 Ergonomics, Manual handling consists of the following parts, under the general title:

   −  Part 1: Lifting and carrying;

   − Part 2: Pushing and pulling;

   − Part 3: Handling of low loads at high frequency.

· ISO 11226, Ergonomics, Evaluation of static working postures, gives recommended limits for static working postures with no, or with minimal external force exertion, while taking into account body angles and duration.

· ISO TR 12295. This Technical Report serves as an application guide of The ISO 11228 series and ISO 11226 that offers a simple risk assessment methodology for small and medium enterprises and for non-professional activities. In the ISO TR12295 the paragraph “C.5 Advances on other methods suggested for a detailed risk assessment” is very relevant for us, since there is a reference to the EAWS[1] system, which is the only ergonomic tool producing a comprehensive load evaluation in the manufacturing sector (body postures, action forces, manual material handling of loads and repetitive motions of the upper limbs).

I am currently working on the development of a ISO Technical Report (TR 23076) with the active participation of the national standardization organizations of Canada, USA, Netherlands, Sweden and, of course, Italy (UNI). My objective is to produce a guide to the industrial engineers for the application of ergonomic work allowances as a means to determine the correct quantity of cyclical work assigned to a worker in a manufacturing plant in order to meet the definition of a fair day’s work. A fair day’s work is that length of working day and that intensity of actual work, which expends one day's full working power of the worker without encroaching upon his capacity for the same amount of work for the next and following days. In the old-fashioned production systems (piecework based) the fair day’s work concept was used in connection with the fair day’s wage. In this report and in our view, the studies about the definition of the fair day’s work become fundamental to connect work-study with the most recent knowledge about biomechanical load (occupational health and safety), with a special focus on the product-process design phase.The industrial sector is one of the sectors with the highest global employment rate (22.5% of total employment). Despite this, the most recent research efforts about the definition of a fair day’s work date back to the 80’s. In the last 20 years a lot of research has been carried out on the biomechanical load and many new standards were created.

This TR wants to be a first bridge between two different fields of knowledge: work study (Industrial Engineering) and occupational health and safety (Ergonomics). The objective is to improve the work study tools by leveraging the knowledge made available by the most recent studies about Work-related Musculoskeletal Disorders (WMSDs).

This TR provides a methodological reference for the procedures to determine the fair quantity of work within a workday in industrial operations with repetitive manual work cycles. The goal of the model is to guide industrial engineers keep the biomechanical load/local muscle fatigue generated by the planned cyclical work withinthe limits defined in the ISO 11228.1/2/3 and 11226.

This TR does propose neither new work measurement techniques nor new ergonomic techniques or standards. Rather, it aims at merging the best available knowledge (I.E. and Ergonomics) about human capacity of accomplishing a manual task, following a pre-defined work cycle (method description and related standard time) without generating an excess of biomechanical load (fatigue).

Present Issues

· Ergonomic Allowance is neglected or assigned based on a partial evaluation of the physical load (usually body postures and forces). The calculation is not influenced by:

   −  Load duration (action frequency and duration of static actions) 

   −  Work organization (shift duration, duration and distribution of the break periods) and work measurement 

· Lack of a well-recognized standard work performance to measure manual work

· Available ergonomic evaluation systems work on different measurement scales and it is hard to assess the overall physical stress

· The Ergonomic approach tends to be used reactively in industry rather than proactively (preventive ergonomics)

Project Scope

The scope of the TR is any cyclical human work planned and executed in an industrial competitive environment. The most typical cases are within industries where there is the need to define an expected output (products or services) based on the optimization of the trade-off between labor productivity and H&S.

The most sensitive organizations to this proposal would be the in the labor-intensive manufacturing industries with series and batch production systems:

· Automotive (OEM and Tier 1 and 2 suppliers)

· Industrial Automotive (trucks, buses, agricultural and mining equipment) 

· Industrial Manufacturing (small domestic and industrial equipment/machinery)

· Domestic appliances and consumer goods (white goods)

· Plastic and rubber products (tires, doors, windows, shoes)

· Consumer electronics (PC, TV-sets, printers, radio, Hi-fi, alarm systems)

· Furniture

· Textile/apparel

· Food preparation

· Packaging

· Aerospace and Defense

· Rail and Ship

· Large domestic and industrial equipment/machinery

· Logistics

Expected Benefits

· Support the adoption of ISO 11228 series and ISO 11226 in the industrial manufacturing sectors

· Support the definition of a standard work performance to standardize the work measurement

· Improve working conditions, safety and ergonomics of workers in manufacturing industries

· Complement the traditional set of the time and motion expert’s capabilities with the ergonomic skills  necessary to design safe and efficient work-stations and to sustain continuous improvement of productivity and ergonomics during the entire product life cycle

· Support the ergonomic evaluation in the earliest stages of product/process development, when changes are still feasible and the cost of a change is affordable (preventive ergonomics)

· Link ergonomic improvements with labor cost reduction (improve ergonomics à reduce costs à justify investments in ergonomic improvements)

· Reduce the cost and the deviation of the ergonomic risk mapping process by linking the biomechanical load measurement with work measurement and organization

· Be an objective reference for the Employers and the Unions when setting up gainsharing contracts based on labor productivity (industrial relations)

Proposed Approach

[1] Ergonomic Assessment Work-Sheet

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