¹Saarland University, Faculty of Medicine, Institute of Occupational Medicine and Public Health, Homburg/Saar, Germany
²Luebeck University, Luebeck, Germany
³Ingenieursbüro Kaulbars, Bonn, Germany
⁴IFA - Institut für Arbeitsschutz, St. Augustin, Germany

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Introduction: Experimental studies on vibration transmission to hand-arm systems often rely on ISO 5349-1. However, for single shock or impact exposures, it remains unclear if the ISO 5349-1 parameter ahw sufficiently describes exposure or if alternative parameters should be considered. Alternative descriptors for shock exposures are suggested in ISO/TS 15694 and by Pitts et al. [1] : ahw,RMS,T, ahw,RMQ,T, ahF,RMS,T, ahF,RMQ,T (T=1s, 3s, or 300s), CFh (crest factor; T=3s, or 300s), SCh (shock content quotient of acceleration, T= 3s or 300s), jT (jerk, T=3s or 300s), and VPM [2].

Methods: 52 male participants were exposed to vibration excitated by a shaker. They were randomly assigned to four exposure groups with 20 min of three single shock exposures (1s⁻¹, 4s⁻¹, 20s⁻¹) or 20 min of control random vibration (4 x 5-minute bouts), with a constant vibration value ahw = 10m/s2 for all exposures. Transmission values at the wrist, elbow, and shoulder were calculated according to ISO standards for all listed exposure parameters. These values were correlated (Spearman), compared across groups (non-parametric Kruskal-Wallis tests with Bonferroni correction), and examined through linear regression models (model fit: adjusted R², beta and T). P-values < 0.05 were considered as statistically significant.

Results: Correlations (r) ranged from -0.451 to +0.981 for wrist, -0.383 to +0.956 for elbow, and from -0.634 to +0.972 for shoulder transmissibility, suggesting varying information content across the selected exposure parameters. Kruskal-Wallis tests indicated that parameters related to ahw identified the 4s⁻¹ shock exposure as distinct. Parameters assessing impacts (CFh, SCh) identified the 1s⁻¹ exposure as different from the other exposure groups, and jerk (j) and VPM distinguished all shock exposures from the vibration exposure group. Linear regression models were partially able to predict wrist, elbow, and shoulder transmissibility, with the best fit found for SCh-transmissibility at the wrist (adjusted R² = 0.879).

Conclusion: The possibility for preventive prediction of health effects from hand-arm shock exposure is still under scrutiny. This study suggests that exposure parameters could differ in their impact on improving understanding of exposure-health associations. Some of the examined parameters also express good model fits for a prediction of transmissibility. These findings further elucidate the complex associations between anthropometry, coupling forces and exposure [1]. Whether the examined parameters also better predict health effects or not requires further investigation.

References

[1] Pitts PM, Kaulbars U, Lindell H, Gretarsson SL, Machens M, Brammer AJ, Yu G, Schenk T, Haas F. Hand-arm vibration: Exposure to isolated and repeated shock vibrations - Review of the International Expert Workshop 2015 in Beijing. IFA Report 5/2017e. [Hand-Arm-Vibration: Expositionen gegenüber wiederholt auftretenden Einzelstößen - Review des International Expert Workshop 2015 in Peking. IFA Report 5/2017e]. Berlin: Deutsche Gesetzliche Unfallversicherung (DGUV);2017.
[2] Pan D, Xu XS, Welcome DE, McDowell TW, Warren C, Wu J, Dong RG. The relationships between hand coupling force and vibration biodynamic responses of the hand-arm system. Ergonomics. 2018 Jun;61(6):818-30. DOI: 10.1080/00140139.2017.1398843