Design options for improving protective gloves for industrial assembly work.

The study investigated the effects of wearing two new designs of cotton glove on several hand performance capabilities and compared them against the effects of barehanded, single-layered and double cotton glove conditions when working with hand tools (screwdriver and pliers). The new glove designs were based on the findings of subjective hand discomfort assessments for this type of work and aimed to match the glove thickness to the localised pressure and sensitivity in different areas of the hand as well as to provide adequate dexterity for fine manipulative tasks. The results showed that the first prototype glove and the barehanded condition were comparable and provided better dexterity and higher handgrip strength than double thickness gloves. The results support the hypothesis that selective thickness in different areas of the hand could be applied by glove manufacturers to improve the glove design, so that it can protect the hands from the environment and at the same time allow optimal hand performance capabilities.

The use of schoolbags and musculoskeletal symptoms among primary school children: are the recommended weight limits adequate?

This cross-sectional study investigated the use of schoolbags and the prevalence of musculoskeletal symptoms among a sample of 307 Iranian primary school children aged 7-12 years. The average load carried by the children was 2.9 kg (representing on average 10.1% of the child's body weight). Most children chose to carry the schoolbag across two shoulders, although significant numbers also carried it on one shoulder or in the hand. Although the amount of load carried by school children was within the currently suggested load limit of 10% to 15% of the child's body weight, the prevalence of musculoskeletal problems was very high among the study population. Multiple logistic regression models indicated that the method of carrying the schoolbag was significantly associated with hand/wrist and shoulder symptoms, and that the time spent carrying a schoolbag was associated with hand/wrist and upper back symptoms. Schoolbag weight (expressed as a percentage of body weight) was only associated with hand/wrist symptoms. The results suggest that the current recommended weight limit may not be appropriate for school children in primary school, and that guidelines ought to consider factors other than relative schoolbag weight that influence the use of schoolbags among this age group. PRACTITIONER SUMMARY: The carrying of schoolbags by primary school children and their musculoskeletal symptoms were investigated. The results provide evidence that the current weight limit may not be appropriate for younger school children, and that such guidelines should consider a broader combination of the factors that influence the use of schoolbags.

Methodology for evaluating gloves in relation to the effects on hand performance capabilities: a literature review.

The present study was conducted to review the literature on the methods that have been considered appropriate for evaluation of the effects of gloves on different aspects of hand performance, to make recommendations for the testing and assessment of gloves, and to identify where further research is needed to improve the evaluation protocols. Eighty-five papers meeting the criteria for inclusion were reviewed. Many studies show that gloves may have negative effects on manual dexterity, tactile sensitivity, handgrip strength, muscle activity and fatigue and comfort, while further research is needed to determine glove effects on pinch strength, forearm torque strength and range of finger and wrist movements. The review also highlights several methodological issues (including consideration of both task type and duration of glove use by workers, guidance on the selection and allocation of suitable glove(s) for particular tasks/jobs, and glove design features) that need to be considered in future research. Practitioner Summary: The relevant literature on the effects of protective gloves on different aspects of hand performance was reviewed to make recommendations for the testing and assessment of gloves, and to improve evaluation protocols. The review highlights research areas and methodological issues that need to be considered in future research.

Using pliers in assembly work: short and long task duration effects of gloves on hand performance capabilities and subjective assessments of discomfort and ease of tool manipulation.

The present study investigated the effects of wearing typical industrial gloves on hand performance capabilities (muscle activity, wrist posture, touch sensitivity, hand grip and forearm torque strength) and subjective assessments for an extended duration of performing a common assembly task, wire tying with pliers, which requires a combination of manipulation and force exertion. Three commercially available gloves (cotton, nylon and nitrile gloves) were tested and compared with a bare hand condition while participants performed the simulated assembly task for 2 h. The results showed that wearing gloves significantly increased the muscle activity, wrist deviation, and discomfort whilst reducing hand grip strength, forearm torque strength and touch sensitivity. The combined results showed that the length of time for which gloves are worn does affect hand performance capability and that gloves need to be evaluated in a realistic working context. The results are discussed in terms of selection of gloves for industrial assembly tasks involving pliers.

Short and longer duration effects of protective gloves on hand performance capabilities and subjective assessments in a screw-driving task.

The study investigated short and longer duration effects of gloves on hand performance capabilities (muscle activity, dexterity, touch sensitivity, finger pinch and forearm torque strength) and subjective assessments of discomfort and ease of manipulation when performing a light assembly task. The independent variables were hand condition with four levels (wearing cotton, nylon or nitrile gloves as well as barehanded) and point of time within the 2 h duration of the task (with measurements taken at 0, 30, 60, 90 and 120 min). Participants worked with a screwdriver to fit two components together using screws. Wearing gloves significantly increased the muscle activity, pinch strength and discomfort but reduced the dexterity and touch sensitivity. There was also a significant effect of task time on the muscle activity, dexterity, forearm torque strength and touch sensitivity, which indicates that the duration of the task should be an important consideration in glove evaluation studies and in the selection of work gloves. STATEMENT OF RELEVANCE: It is important to evaluate the effects of gloves on hand performance capabilities in a working context so that job demands can be taken into account and the most appropriate type of glove be chosen for each task. This study gives recommendations regarding the evaluation and use of gloves for screw-driving tasks.

Ready steady push--a study of the role of arm posture in manual exertions.

This study investigated arm posture and hand forces during bi-manual pushing. Nine male and eight female participants performed isometric exertions at two reach distances (0 and elbow-grip) and six different positions of the hand interface (handle), defined by the plane (longitudinal, lateral, horizontal) and orientation (0 degrees and 45 degrees). Electrogoniometer instruments were used to measure the displacements/postures of the wrist and elbow joints and the forearm, and force measuring strain gauges were used to measure the exerted hand forces (x-, y- and z-components). The results showed that ability to vary arm posture, particularly the forearm, is important during build up of force and that people tend to seek for a balance in the forces applied at the hands by exerting more in the vertical direction. Also, lateral plane handle positions permitted exertion of greater forces than longitudinal and horizontal plane positions.

Developing a verbal protocol method for collecting and analysing reports of workers' thoughts during manual handling tasks.

Concurrent and retrospective verbal protocol methods were used to collect thoughts from 18 participants during a manual handling task involving the repeated transfer of loads between locations at two tables. The effectiveness of qualitative and quantitative methods of analysing the reported information was tested in the study. A simple taxonomy was developed to investigate the content of the reports (including reports on postures and loads) and determine how the participants approached the task (whether they made plans, described actions or evaluated their completion of the task). References to posture were obtained in the verbal protocol reports, indicating that the participants had some awareness of their postures during parts of the task. There were similarities in the content of the concurrent and retrospective reports, but there were differences in the amount of detail between the methods and differences in the way the reports were constructed. There could be some scope for developing the quantitative analysis of the frequencies of references to classes of information, though this can only be recommended for concurrent reports on tasks of short duration. The analyses of qualitative data gave a deeper insight into the reports, such as identifying factors that can be important when planning to handle a load, or illustrating how participants can change their focus of attention periodically throughout the task. The relative strengths of the concurrent and retrospective methods are described, along with ideas for improving the quality of information collected in future studies. A number of potential problems with the interpretation of the reported information are explained.

Use of concurrent and retrospective verbal protocols to investigate workers' thoughts during a manual-handling task.

A manual handling task (an order picking task in a distribution warehouse) was investigated using concurrent verbal protocols and retrospective verbal protocols (applied at three different times after completion of the task). The study aimed to collect workers' thoughts during the task and to determine what workers are comfortable with reporting. Video recordings of the task were used as a means of investigating the accuracy of the information which was reported. The concurrent and retrospective verbal protocol methods were compared and it was found that concurrent reports could be used to collect a range of task related thoughts, although they only contained a proportion of the workers' thoughts during the task. Additional information could be obtained from retrospective reports, although these appeared to be vulnerable to bias and re-ordering of reported information. The retrospective reports produced whilst watching a video recording of the task were particularly vulnerable to bias from retrospective reasoning or the rationalisation of thoughts. Only one specific reference to posture or handling technique was made by any of the workers in their reports. There were also few references to load characteristics. Workers frequently reported aspects of the task that were easier to verbalise, such as the counting or labelling of items. It is not known whether the workers were only aware of these limited details of their tasks or whether they were only able to report limited details of the tasks because of factors affecting verbal reporting. This was an exploratory study which has collected valuable information from a small sample of experienced workers in relation to a common task from industry, but further study is needed to investigate the effects of factors such as load weight, load position and task duration on awareness and reporting of thoughts.

Postures adopted when using a two-wheeled cylinder trolley.

Upper limb and trunk positions were investigated when subjects exerted force to start and move a two-wheeled cylinder trolley with four different handles. Three of the handles had orientations 35 degrees, 50 degrees and 70 degrees in the sagittal plane (relative to the back of the trolley). The fourth was the 50 degrees handles fitted with a link bar. Measurements were made of x (horizontal), y (lateral) and z (vertical) coordinates of the body joints in space throughout the motion, using a CODA MPX30 optical 3-D measurement system, and both linear and angular displacements were computed. The linear and angular positions of the body joints were found to change through the stages of the task. Orientation of the handle influenced the arm postures adopted in the task, and showed to produce different patterns of arm displacement in force exertion to tilt the trolley from standing position. For steady movement, the sagittal plane 50 degrees handle proved most desirable.

Pouring liquid from a pot-kinematics of an everyday task.

An experiment was carried out to investigate the effects of handle design on postures in the use of pots. Six combinations of handle (sloping, vertical and curved) and spout designs (long and short) were tested during grasping, lifting and pouring. The fill load was 1000 ml of water at the prevailing room temperature (about 20 degrees C) and three males and three females were involved as subjects. Measurements were made of x- (horizontal), y- (lateral) and z- (vertical) co-ordinates of the wrist, elbow shoulder and hip joints in space throughout the motions, using a CODA MPX30 optical 3D measurement system and both linear and angular displacements of the arm joints and trunk were computed. Very different configurations of arm posture were found to be adopted at the moment of pot lift, and when pouring commences and the subjects' movement patterns during transfer of the pot to fill vessel showed to be influenced by the configuration of arm posture adopted at the moment of pot lift. For lifting the pot, the vertical handle design proved to be more desirable than either the curved or sloping design, while for pouring from the pot the short spout proved to be more desirable than the long spout, at least when the pot was full. The results are however, not clear on which handle or spout design is best for transferring the pot.