An Investigation of the Effects of Drill Operator Posture on Vibration Exposure and Temporary Threshold Shift of Vibrotactile Perception Threshold

Abstract

The present study involved performing an experiment to clarify whether vibration measurement values on the tool handle, in accordance with ISO 5349-1, can assess risk from workplace environments. The study investigated the relationship between the vibration magnitude of a hand-held electric drill with different operating postures. The experiment included the determination of the participant’s temporary threshold shift (TTS) of vibrotactile perception threshold (VPT) at the tip of the index finger. The experimental hypothesis was that the vibration measurement values on the tool handle, in accordance with the ISO 5349-1 standard, include the effect of posture on the vibration measurements obtained despite the variation in posture and test participants. The hand-transmitted vibration (HTV) was applied using a hand-held electric drill applied to a pre-cast concrete paving slab substrate (600 × 600 × 50 mm, 55 MPa) using a 10 mm diameter masonry drill bit (without hammer action). The tool was operated using the right hand on twelve male subjects with three working postures (n = 36). Vibration was measured in three orthogonal directions according to the international standard ISO 5349-1 procedure. Vibration magnitudes were expressed as root-mean-square (r.m.s.) acceleration, frequency-weighted using the Wh frequency weighting. Clause 4.3 states that the characterisation of the vibration exposure is assessed from the acceleration of the surface in contact with the hand as the primary quantity. The experimental results indicate that the TTS following vibration exposure is not related to the measured vibration magnitude on the tool handle. Therefore, the automatic inclusion of posture and test participant variation is not proven. The results suggest that the vibration measurement values on the tool handle do not predict the TTS after hand-transmitted vibration in varying posture across the test participants. The research concludes that tool handle vibration measurement, in accordance with ISO 5349-1, does not properly assess the potential hazard from authentic workplace tool usage conditions of varying postures.

Vibration transmitted to the hands of power drill operators: Effect of arm posture and type of drilled material

“…The effect of arm posture on the total acceleration measured at the tool handle is consistent with previously reported results where certain operating postures were reported to increase the vibration acceleration at the handle of the tool. 16 Some adopted hand-arm postures can increase the quasi-static stresses, strains, and deformations of the tissues leading to altering the vibration transmission through the hand-arm system and increasing the potential development of HAVS or other vibration-induced muscle injuries. 9 However, it has to be noted that other studies conducted with hand-held grinders did not find any significant differences in the frequency-weighted acceleration at different parts of the hand-arm system with different working postures which may imply that the effect of the hand-arm posture on the vibration transmitted to the hand-arm system is dependent on the operated power tool.…”

“…A recent study has investigated whether the effect of the posture of the operator of an electric drill is included in the vibration measured on the handle of the drill. 16 The results showed that the vibration measured on the tool handle could not predict the temporary threshold shift of vibrotactile perception threshold after the exposure to vibration with different postures and hence, the study concluded that measurement of vibration on the handle of the drill using ISO 5349-1 22 does not include the effect of the operator posture. This has an implication on the suitability of using the current standard for assessing the potential hazard from power tools at varying postures.…”

“…In addition to the effect of the operator posture, the effect the hand-arm posture of the operator of the power tool on the biodynamic responses to vibration has been widely investigated. 7,[16][17][18]23 It was reported that the effect flexion angle between the upper arm and forearm depend on the vibration frequency: below 25 Hz, flexion angle of 180°amplified the vibration transmissibility to different locations on the arms compared to flexion angle of 90°while an opposite trend was observed at frequencies above 25 Hz. 7 Additionally, the hand-arm posture showed effect on the driving point mechanical impedance of the handarm system.…”

“…Understanding the biodynamic response to vibration is essential for understanding the effect of vibration on comfort and health leading to developing better risk assessment procedures. 4–9 The biodynamic responses of the hand-arm system to vibration were primarily studied and expressed using the following three methods: (1) measuring the vibration acceleration at the source of vibration and/or measuring the transmissibility from the power tool to the hand and/or arm 7,10–16 ; (2) measuring the apparent mass (or mechanical impedance) or the absorbed power by the hand-arm system 5,6,17–20 ; and (3) building mathematical models that represents the biodynamic response of the hand-arm system to vibration. 4,8,21 Most of those studies were conducted in a laboratory setup but have significantly enhanced the knowledge of HAV influencing factors, such as operator posture, hand-arm system posture, grip and push forces, and direction and magnitude of vibration.…”

Does the Workload Change When Using an Impact Wrench in Different Postures?—A Counter-Balanced Trial

“…To show the influence of posture during hand-arm vibration exposure, different approaches such as magnitude of the vibration and feed and gripping forces for different working directions are applied [10][11][12][13]. While significant lower vibration magnitude was measured for working horizontally compared to vertical directions [12], significant influence of the body posture on the acceleration of the main handle was shown by means of feed and gripping forces [13].…”