Occupational Ergonomics

It is well known that prolonged sitting can elicit low back pain as a result of the abnormal shape of the spine. This problem becomes worse in whole-body vibration environments where a rocking motion of the pelvis can occur and may amplify the vibration motion transmitted to the lumbar spine.

Although the use of lumbar supports is common in static environments, little is known about how the use of such supports changes the biodynamic response and discomfort of the person in whole-body vibration environments.

The motion at the head and the discomfort of ten participants were recorded under five back-support conditions, including three commercially available lumbar supports.

The results indicated significantly lower head motion and discomfort (p < 0.05) with the use of the lumbar supports than with a simple flat backrest.

All lumbar supports used in this study combined the advantages of reduced head motion and reduced discomfort during whole-body vibration.

Heavy mobile equipment operation exposes operators to whole-body vibration (WBV) through the seat. The decision of which seat to retrofit a machine with is usually done statically.

To report on the third phase of a three phase project designed to intelligently retrofit seats in heavy mobile machines with the purpose of reducing machine operator WBV exposure.

Three slag pot haulers were retrofitted with a 6801 Isringhausen seat in which the seat pan cushion was retrofitted with Skydex^TM seating material. Vibration dose values (weighted for health), vibration total values (weighted for comfort) and Seat Effective Amplitude Transmissibility were determined from field measurements.

WBV was reduced from the first field study to below the upper boundary of the ISO 2631-1 (1997) health guidance caution zone and comfort weighted vibration total values were reduced to the second lowest discomfort rating.

Steel making and other similar industries have been provided with information to more efficiently retrofit existing machines.

Fingers-transmitted vibration can cause vibration-induced white finger. The effectiveness of vibration-reducing (VR) gloves for reducing hand transmitted vibration to the fingers has not been sufficiently examined.

The objective of this study is to examine tool-specific performance of VR gloves for reducing finger-transmitted vibrations in three orthogonal directions (3D) from powered hand tools.

A transfer function method was used to estimate the tool-specific effectiveness of four typical VR gloves. The transfer functions of the VR glove fingers in three directions were either measured in this study or during a previous study using a 3D laser vibrometer. More than seventy vibration spectra of various tools or machines were used in the estimations.

When assessed based on frequency-weighted acceleration, the gloves provided little vibration reduction. In some cases, the gloves amplified the vibration by more than 10%, especially the neoprene glove. However, the neoprene glove did the best when the assessment was based on unweighted acceleration. The neoprene glove was able to reduce the vibration by 10% or more of the unweighted vibration for 27 out of the 79 tools. If the dominant vibration of a tool handle or workpiece was in the shear direction relative to the fingers, as observed in the operation of needle scalers, hammer chisels, and bucking bars, the gloves did not reduce the vibration but increased it.

This study confirmed that the effectiveness for reducing vibration varied with the gloves and the vibration reduction of each glove depended on tool, vibration direction to the fingers, and finger location. VR gloves, including certified anti-vibration gloves do not provide much vibration reduction when judged based on frequency-weighted acceleration. However, some of the VR gloves can provide more than 10% reduction of the unweighted vibration for some tools or workpieces. Tools and gloves can be matched for better effectiveness for protecting the fingers.

Exposure to hand operated vibrating tools in the construction industry places workers at risk for developing hand-arm vibration syndrome (HAVS), which is a common occupational disease.

To outline health and safety training obtained by construction workers and to assess which factors influence anti-vibration (AV) glove utilization following an educational intervention provided during a clinical assessment for HAVS at an occupational health clinic.

One hundred participating workers from the construction industry referred for a HAVS assessment at a hospital-based ambulatory occupational health clinic in Toronto, Ontario, Canada. A baseline and two-month follow-up questionnaire were completed.

Almost all of the participants indicated that they had completed health and safety training within their workplace. However, few received training specific regarding HAVS or AV gloves. Participants’ AV glove use improved from 4.3% at baseline to 53.3% at follow-up two months later. Key predictors of participants wearing AV gloves was sharing the educational intervention information with their supervisors and working in a workplace with 20 or more employees.

Training specific to HAVS and AV gloves is lacking in the construction industry. The educational intervention proved most effective in increasing AV glove use when the information was shared within the workplace.

Exposure to foot-transmitted vibration (FTV) has been linked to injury; however, the biodynamic response of the foot to FTV has not been quantified.

The objective was to measure vibration transmissibility from the floor-to-ankle, and the floor-to-metatarsal, during exposure to FTV while standing, and to determine if FTV exposure frequency, or participant mass or arch index (AI) influence the transmission of FTV through the foot.

Participants’ AI was measured. Four ADXL326, tri-axial accelerometers were utilized to measure vibration on the platform medial to distal head of first metatarsal, on the distal head of first metatarsal, on the platform paralleling the medial malleolus, and on the lateral malleolus. Participants were randomly exposed to FTV at 25 Hz, 30 Hz, 35 Hz, 40 Hz, 45 Hz, and 50 Hz for 45 seconds.

Neither the three-way interaction of location*frequency*AI [λ = 0.816, F(5,24) = 1.080, p= 0.396] or location*frequency*mass [λ = 0.959, F(5,24) = 0.203, p= 0.958] were significant (p< 0.05). The location*frequency interaction was significant [λ = 0.246, F(5,25) = 15.365, p= 0.0001]. Differences in mean transmissibility between the ankle and metatarsal were significant at 40 Hz, 45 Hz, and 50 Hz (p< 0.001).

The greatest transmissibility magnitude measured at the metatarsal and ankle occurred at 50 Hz and 25-30 Hz respectively, suggesting the formation of a local resonance at each location.