The Italian legislation on occupational safety (D.LGS 81/2008) requires the elimination or, if not possible, the reduction of the risk of biomechanical overload and work-related musculoskeletal disorders. The national and local strategies for occupational safety provide guidelines and directions to promote the safety culture in workplace.
The prevention of musculoskeletal injuries and disorders due to biomechanical overload includes the application of the ergonomic principles for the workplace design and organization. Job activities, tasks and the work environment should be designed to limit the exposure to ergonomic risk factors by taking preventative measures.
Following these principles, employers adopt the organizational measures needed and proper equipment, providing the adequate devices that the technical progress and the experience have produced.
The aim of this Solutions Database is to provide useful directions for the choice of effective and available preventive measures (technical, organizational and procedural) for manual material handling of loads (animated and not), repetitive movements and strains and awkward postures leading to the biomechanical overload. This work aims to promote the introduction of technical measures and recall the presence of important protective measures as:
- information, formation (general and specific), training for the proper use of equipment and devices, and safe manual movement;
- preventive and regular occupational health surveillance, following the effective and validated protocols;
In particular, information, formation and training improve the risk perception and the ability to recognize the risk characteristics, simplifying the adoption of procedural and organizational measures, and allowing the proper use of technical solutions. The effective health surveillance policy and the collaboration with the occupational health doctor allow the early detection of possible signal failures of primary prevention measures, together with sustainable work conditions for the reintegration of workers who experienced the consequences of the failure.
The detailed assessment of the risk factors ( e.g. use of force/exertions, repetitiveness, forced postures, time/pace/rest, organizational constraints, etc.) and the reasonable adjustment to the work conditions may avoid the appearance or the worsening of work-related disorders, allowing the inclusion and/or the reintegration of workers with medical conditions and individual risk factors. Effective prevention must produce tangible results in terms of health and safety, as prescribed by the Evidence Based Prevention (EBP) criteria.
The Ergonomic Approach
The ergonomic design of workplaces and workstations allows the fit of the work environment to people’s characteristics, necessities, abilities and limitations. The application of the ergonomic principles for work organisation, workplaces conception, choice of the equipment and design of work and production methods (art. 15 comma 1 lettera d) D.Lgs 81/08) prevents the development of injuries and disorders, mainly affecting the musculoskeletal system. The knowledge and the application of the basic ergonomic principles, together with the technical and measures, are necessary for the design and the re-design or workplaces or to realize effective safety procedures. The aim is the immediate elimination of high-risk conditions and the reduction of the risk exposure, to achieve acceptable work conditions.
See the following for some basic principles, a list of high-risk conditions and a list of acceptable conditions from the ergonomics standards (Attached 1).
SOME BASIC PRINCIPLES
The functional recovery is a period of rest which allows the restoration of the musculoskeletal functions of upper-limbs and back to reduce the risk due to repetitive movements or manual handling:
- the upper-limbs require a functional recovery from 1 to 5 for a total time of one minute minimum (10 seconds of recovery and 50 seconds of repetitive work – micropause) and a total time of one hour maximum (10 minutes of recovery and 50 minutes of repetitive work). The optimal result for this risk factor is possible if functional recovery of the limbs is possible during the whole working time;
- the back requires a functional recovery of one hour for every hour of manual material handling. The time for pulling and pushing activities is not considered as functional recovery.
Maximum lifting weight
The maximum weight that a worker (male, age between 18 and 45) is allowed to lift is equal to 25 kg in ideal conditions. Ideal conditions refer to ideal posture (the center of gravity of the weight is not higher than 25 cm from the knuckles and not further than 25 cm from the vertebral column), the grip is good, the weight is balanced and lifting is performed with two hands, and microclimatic conditions are comfortable (in particular not too hot).
In the same ideal conditions, the maximum weight for a woman with the same age or for a man younger than 18 or older than 45 is equal to 20 kg. Women younger than 18 and older than 45 in ideal conditions are allowed to lift 15 kg maximum.
The maximum weight that a worker is allowed to handle in a 8-hours work day (cumulative weight) is equal to 10000 kg, when the travelled distance is between 0 and 10 m. For longer distances, worse ergonomic conditions and harder microclimatic conditions such values reduces. The reference standard (ISO TR 12295) defines the maximum cumulative weight by hour and minute.
Strength
The strength required to perform a repetitive task with the upper limbs, for long or short time periods, must be minimum. When tasks require peak forces, electric, pneumatic or hydraulic equipment are required in order to eliminate the worker’s manual force. The application of such technical measures strongly reduce the incidence of related injuries.
Frequency
The frequency of manual material handling cannot be higher than 15 lifts/minute, for 2 continuous hours maximum. Manual material handling is occasional if lower than one movement every 5 minutes. If manual material handling is occasional, in ideal conditions and within the aforementioned weight limits, then the risk is acceptable.
Work activities with a frequency of 30 actions/minute without additional risk factors (postures, recovery, strength) pose an acceptable risk for upper-limb disorders.
HIGH-RISK CONDITIONS
Lifting and carrying
- The hand position at the beginning and end of lifting is higher than 175 cm or lower than 0 cm from the height of the worker’s feet;
- The horizontal distance between the body and the load is longer than the arm range of motion (> 63 cm);
- Extreme rotation of the body (angle > 135° with no movement of the feet);
- Lifting frequency higher than the maximum allowed for the lifting task (ex. 8 lifts/minute for more than 120 minutes; 15 lifts for tasks of 2 hours maximum);
- Loads heavier than the maximum allowed weights, by gender and age (15-20-25 kg);
- Cumulative weight higher than the allowed limits, by duration and travelled distance (ex. higher than 10000 kg in 8 hours for distances longer than 20 m);
- The lifting and/or carrying path contains stairs.
Pulling and pushing
- Necessity to use maximal forces (≥ 8 on Borg scale) to overcome the static friction, to accelerate, to decelerate or to maintain the movement;
- Rotate or bend the trunk significantly; hands outside the shoulder width; hands not in front of the body; hands over 150 cm and below 60 cm;
- Slippery (kinetic friction coefficient < 0.40 μ) and irregular (due to holes and cracks) floor.
Repetitive tasks
- Technical actions, with one or two arms, so fast that the direct observation and their count are difficult;
- One or both the arm work with the elbow at the shoulder height for the 50% or more of the duration of the task;
- Pinch hand positioning for more than the 80% of the duration of the repetitive task;
- Force peaks (≥ 5 on Borg scale) for the 10% of the overall duration of the repetitive task;
- One break in a 6-8 hours shift;
- Overall duration of the repetitive tasks longer than 8 hours.
ACCEPTABLE CONDITIONS
Lifting and carrying
- Weight between 3 and 5 kg, maintained close to the body, between hips and shoulders, no asymmetry and no more than 5 lifts/minute;
- Weight between 5 and 10 kg, maintained close to the body, between hips and shoulders, no asymmetry and no more than 1 lift/minute;
Pulling and pushing
- Need to use minimum force (≥ 2 on Borg scale), keeping the hands within the shoulder width and in front of the body, between the hips and half trunk, in upright position (trunk not bended or rotated), no longer than 8 hours.
Repetitive movements
- The repetitive task is performed for no more than 8 hours/day and meeting the following conditions: upper-limbs work for less than the 50% of the overall duration of the repetitive task; elbows are below the shoulders for the 90% of the overall duration of the repetitive task; no force peaks (higher than 5 on Borg scale); use of moderate force (3 or 4 on Borg scale) for no more than 1 hour (total time); breaks are between 8 and 10 minutes every 2 hours, additional to the lunch break; upper-limbs do not touch surfaces with temperature lower than 0°C.
Organisational and Procedural Solutions
Organisational and procedural solutions mainly are measures to improve an unfavorable work condition due to the inadequancy of one of the following elements or their combination: action frequency, duration of the task, ratio and distribution of the time for functional recovery and working time, rotation between tasks.
The consultation of the workers and of their representatives precedes the adoption and the formalization of procedures, operative instructions, guide lines, prohibitions or other effective practices [1] (properly formalised). Every worker must be aware of such procedures and receive the proper formation/training.
The following show some details on the adoption of organisational measures:
- if the solution consists in “lifting by two people”, then two people must be present and available;
- if breaks (functional recovery) are adopted for the risk reduction, such breaks must be well-defined, formalised, respected and be not a burden;
- if workers rotate among different workstations, differently overloading (ex. alternation between repetitive tasks and visual inspection), the times and the methods of such rotations must be well-defined
- if no available technical solutions are adopted and no breaks are included during the work-shift, the reduction of workdays cannot be an organisational measure for the risk reduction.
An effective technical solution, if well defined and applied, has good chances to be adopted.
An organisational or procedural solution must be constantly adopted to be effective, but it could collide with productivity goals. Aiming to implement an effective preventive strategy, all the involved positions and roles must activate a proper surveillance service to ensure the proper use of devices and equipment for the risk reduction and the tangible application of the organisational and procedural measures.
[1] Ref. artt. 28, comma 2, lettera d) e 33, comma 1, lettera c) del D.Lgs 81/08.
___
Go to Technical Solutions for Ergonomics
Go to Attached 1