Biodynamic responses of the human hand-arm system under nail gun shock vibration and differences between males and females

Occupational exposure to vibration from hand tools poses significant health risks, potentially leading to chronic disorders affecting nerves, muscles, and joints in the Hand-Arm System (HAS). Despite extensive research, the biodynamic response of the HAS to real-world shock vibrations remains insufficiently characterized, limiting effective risk assessment and prevention strategies. This study quantifies the biodynamic response of male and female HAS during standardized nail gun operation. Thirty participants (15 males, 15 females) performed standardized nail gun tasks while vibration transmissibility was measured between the tool handle and the wrist, forearm, upper arm, and shoulder using triaxial accelerometers. Results show a consistent decrease in peak transmissibility frequency from the wrist to the shoulder, reflecting a shift in biodynamic response along the HAS. Modal analysis identified distinct natural frequencies across the HAS, with statistical analyses showing significant sex-related differences, particularly in lower-frequency modes. These differences remained significant after adjusting for age, hand length, palm width, and Body Mass Index, confirming the sex-specific biodynamic differences. The importance of a sufficiently large and balanced sample for reliably detecting sex-related effects is demonstrated. The findings highlight the importance of evaluating vibration exposure under realistic conditions, as conventional shaker excitations may not fully replicate the dynamics of shock vibrations. Notably, transmissibility increased at high frequencies and decreased below 10Hz, likely due to differences in experimental conditions. Furthermore, the observed sex-related differences support the need to incorporate sex-specific considerations into occupational health guidelines, ergonomic tool design, and exposure standards to reduce vibration-induced health risks and improve worker safety.