In-Line Power Screwdrivers Recoil: A Pilot Computational Methodology to Assess Differences Among Workstations from a Human-Centric Perspective

Abstract

Background/Objectives: Mechanical shocks generated by the recoil of hand-held power screwdrivers are a significant biomechanical stressor for the operator’s hand–arm complex. Currently, vibration exposure is measured at the tool-handle level, while operator-centered practical measures remain limited. This study proposes a computational methodology to quantify relative reductions in mechanical shock and biomechanical load across different workstations. Using wearable inertial measurement units, ratios of transmitted torque and worst-case wrist joint power were calculated directly at the operator’s upper limb, without direct force measurement. Methods: The methodology was tested with 30 participants performing standardized fastening tasks across five configurations: one unsupported and four with distinct support arms, paired with an electric and pneumatic in-line screwdriver. Results: Workstation configuration had a significant main effect on both the peak angular acceleration and the peak wrist angular velocity (p < 0.001 for both variables). Compared with the unsupported condition, all support-arm configurations substantially reduced the mechanical shock transmitted to the operator, decreasing the estimated transmitted torque by 71–81% and the worst-case wrist joint power by more than 95% (p < 0.001 for all pairwise comparisons). The articulated arm induced higher kinematic responses than telescopic and Cartesian designs. Age was the only significant covariate for hand peak angular acceleration (p = 0.039). Conclusions: The proposed methodology provides a simplified operator-centered approach for assessing mechanical shock transmission during screwdriving operations using wearable IMUs. This methodology may serve as a preliminary screening tool to support workstation design and ergonomic investigations. However, the present findings do not establish a direct relationship between the proposed indices and musculoskeletal disorder risk, and further validation against established ergonomic and clinical outcomes is required.