Biodynamic Response at the Palm of the Human Hand Subjected to a Random Vibration

Abstract

This study investigated the biodynamic response (BR) distributed at the palm of the hand subjected to a random vibration. Twelve male subjects were used in the experiment. Each subject applied three coupling actions (grip-only, push-only, and combined grip and push) on a simulated tool handle at three different levels (50, 75, and 100 N) of palm force. This study found that the hand-arm system resonated mostly in the frequency range of 20 to 50 Hz, depending on the specific test treatment and individual characteristics. The maximum vibration power transmission through the palm occurred at the resonant frequency. Increasing the effective palm force generally increased the BR magnitude and resonant frequency. The apparent stiffness measured at the middle frequencies (80-100 Hz) is correlated to the BR in almost the entire frequency range (20-1,000 Hz). Under the same palm force, the push-only action corresponded to the highest BR values while the grip-only action generally produced the lowest values. Since the resonant frequency range matches the dominant vibration frequency range of many percussive tools, it is anticipated that the palm BR and vibration power transmission may have an association with vibration-induced injuries or disorders in the wrist-arm system among the workers using these tools.

Recent Advances in Biodynamics of Human Hand-Arm System

“…Both the driving-point response data 13,47,67,70) and the vibration transmissibility data 53,54,71) indicate that the resonance of the system in the z h -direction 7) (along the forearm direction) is usually in the range of 16 to 63 Hz, depending the applied force and hand and arm postures. This resonant feature supports the proposed palm theoretical model 49) . It, however, contradicts the flat response phenomenon shown in some previously reported data 63) .…”

“…The results also show that the eigen-frequency corresponding to a specific mode increased almost linearly with the magnitude of the static deformation, irrespective of the mode of vibration. The simulations are consistent in their trends with the experimental observations by many investigators 13,[46][47][48][49] , who reported that the resonant frequencies of the fingers and hand increased with increases in the applied forces.…”

“…The frequency domain method can not only resolve this issue, but it can also simplify the measurement system and reduce the cost. Hence, they further refined this method and used it in their other studies 12,13,48,49) . This method has also been adopted by several other investigators 70,74) .…”

“…In the last few years, some fundamental characteristics of the driving point responses have been clarified. A study suggested that the palm soft tissues actually function like a natural cushion for the hand-arm system 49) . Hence, they can be modeled as a spring-damping system and the remaining structures of the palm-wrist-arm system as a massspring-damping system that is connected to the palm model.…”

Effect of vibration frequency on agonist and antagonist arm muscle activity

“…These differences could have affected in a different way the biodynamic response of the finger-hand-arm system during vibration exposure and the vibration transmissibility to the target muscles (Aldien et al 2006;Dong et al 2004Dong et al , 2005. This leads us to conjecture that the higher effective palm force while pushing the vibratory bar might have favored a larger vibration power transmission to the upper extremity (Dong et al 2005) compared with pulling, which in turn resulted in greater agonist activation of the TB. However, the observed vibration-induced increase in TB agonist activation was only significant at the higher f out of 42 Hz.…”