The upper extremity attenuates intermediate frequency vibrations

Vibration is related to reports of low back pain; however the biomechanics of vibration transmission through the hand-arm system has not been previously studied. Vibration was recorded on an accelerometer mounted to a pin percutaneously imbedded in the spinous process of L4 of five human subjects. The energy was applied through an impact via a pendulum. The subjects adopted an erect, relaxed or bent knee posture. The first resonance was 4–6 Hz and the second at 9–14 Hz. With the knee bent, the signal was almost completely attenuated. If the impact was applied through a handle and the hand-arm system there was complete attenuation.