Fast-roping: potential consequences of vibrations for sensation and regulation of movement.

Abstract

Short-term exposure (2?30 seconds) to segmental mechanical vibrations with frequencies between 20 and 80 Hz affects proprioception of the central nervous system and manual dexterity and strength of man. It could be supposed that during fast-roping, Soldiers are exposed to hand?arm vibrations caused by the geometry of the rope. After the maneuver, Soldiers are encouraged to operate with high precision (e.g., aiming and shooting) within a few seconds. For safety, disturbances of the sensory system should be strongly avoided. The purpose of the study was to determine the vibrations induced by different rope geometries during fast-roping. Eight men of the German Special Forces performed 10 fast-roping maneuvers with two different shaped ropes (slightly molded versus deeply molded). Vibration data and frequency spectrum for each trial were measured by using fast Fourier transformation. The analysis of data showed that fast-roping with a slightly molded rope produced frequencies of up to 10 Hz, while the frequencies with a deeply molded rope accounted for 18 to 60 Hz. The ropes differed significantly (p<.001) in frequencies between 20 and 50 Hz. The exposure time of vibration lasted between 3 and 5 seconds. Considering the negative effects associated with vibrations, prudence is required when using deeply molded ropes due to the increased vibrations of about 20 Hz.