Ergonomic Benefits of an Angle Grinder With Rotatable Main Handle in a Cutting Task

OBJECTIVE

The aim of this study was to evaluate the ergonomic benefits of an angle grinder with a rotatable main handle in a cutting task.

BACKGROUND

Angle grinder manufacturers rarely address ergonomic features in their advertisements, and if they do, the benefits are expressed in a qualitative manner. Meanwhile, quantitative information about the effects of the device on the worker is required to make informed decisions during tool selection and cumulative trauma prevention.

METHOD

Eleven maintenance workers and metalworkers used an angle grinder to cut a horizontal steel rod using three wrist postures. Only one of the postures was exclusively available in the case of a rotatable main handle. The postural effect was evaluated objectively with electromyography and a force-sensing-resistor-based force glove. Subjective ratings about discomfort and control were obtained with a visual analog scale.

RESULTS

The subjective ratings favor the near-neutral wrist posture. The forearm muscles' electromyographic activities were similar across the postures. Forces on the hand-handle interface were concentrated on the intermediate phalanges. If the device is operated without gloves, the forces on the intermediate phalanges may exceed the discomfort pressure threshold regardless of wrist posture.

CONCLUSION

In the cutting task, the subjective measures favor the posture with a near-neutral wrist, which is a feature of the rotatable main handle. The objective measures did not allow one to prefer one posture to another.

APPLICATION

The findings give insight into the impact of wrist posture on muscle activity, forces on the hand-handle interface, and discomfort. This is useful information for the person responsible for tool selection.

In-vehicle noise exposure among military personnel depending on type of vehicle, riding compartment and road surface

Introduction

Noise-induced hearing loss is one of the most common health problems among military service personnel. Exposure to noise in military vehicles constitutes a large proportion of total noise exposure. This pilot study aimed to evaluate in-vehicle noise levels depending on the type of vehicle, riding compartment and road surface.

Method

Noise levels were measured in armoured personnel carriers and heavy all-terrain trucks, in the cab and rear passenger compartment, while driving on paved or off-road surfaces. The results were compared with national LLV and allowed noise exposure times were calculated per vehicle and surface.

Results

The equivalent noise levels in the cab of SISU XA-188 (p=0.001) and peak noise levels in MAN 4620 (p=0.0001) and DAF 4440 (p=0.0047) were higher on paved road, compared with off-road. The equivalent noise levels in the canvas covered rear compartment of MAN 4620 were significantly higher than in the cab on both paved (p=0.004) and off-road (p=0.0003). Peak noise levels in the cab of DAF 4440 exceeded the parameters measured in the canvas covered rear compartment on both paved (p=0.002) and off-road (p=0.0002). In most cases, peak noise levels were below the LLV (p=0.02–0.0001). The maximum noise exposure to passengers in the canvas covered rear compartment of MAN 4620 despite road surface was calculated 0.6 hours per working day.

Conclusion

A high risk of noise-induced hearing loss among military personnel occurs during long distance transportation with vehicles showing noise levels higher than allowed LLV.