Page 90 - Journal of Special Operations Medicine - Summer 2014

Fast-Roping:
Potential Consequences of Vibrations

for Sensation and Regulation of Movement

Jan-Peter Goldmann, Dr.; Bjoern Braunstein, Dr.; Maximilian Sanno, Dipl. Degree;
Stefan Kurzner, Police Chief Inspector; Gert-Peter Brüggemann, Prof. Dr.; Joachim Mester, Prof. Dr.

ABSTRACT
Objectives: Short-term exposure (2–30 seconds) to seg- the biologic effects of vibration. The effects of mechani-
1
mental mechanical vibrations with frequencies between cal vibrations on man are a complex phenomenon. If
20 and 80 Hz affects proprioception of the central ner- a muscle is exposed to vibration, the primary endings
vous system and manual dexterity and strength of man. of the muscle spindle (Ia afferents) are stimulated. This
It could be supposed that during fast-roping, Soldiers excites α-motoneurons and causes contraction of mo-
are exposed to hand–arm vibrations caused by the ge- tor units, which results in tonic muscle contraction.
2–5
ometry of the rope. After the maneuver, Soldiers are During exposure to vibration, the stretch-reflex (muscle
encouraged to operate with high precision (e.g., aim- activity in response to sudden stretching, which pro-
ing and shooting) within a few seconds. For safety, vides automatic regulation of muscle length) and the
disturbances of the sensory system should be strongly Hoffmann-reflex (electrically induced reflex analogous
avoided. The purpose of the study was to determine the to the mechanically induced stretch-reflex) are inhib-
vibrations induced by different rope geometries during ited. Long-term effects of vibration (e.g., Raynaud’s
6–8
fast-roping. Methods: Eight men of the German Special disease, hand–arm vibration syndrome) on the hands
Forces performed 10 fast-roping maneuvers with two and arms are widely investigated. 9,10 But, due to the
different shaped ropes (slightly molded versus deeply complexity of the biologic system and the discrepancy
molded). Vibration data and frequency spectrum for of vibration waveform, the mechanism of the interac-
each trial were measured by using fast Fourier trans- tion between vibration and biologic response remains
formation. Results: The analysis of data showed that mostly unclear. 11,12 However, it is discussed that expo-
fast-roping with a slightly molded rope produced fre- sure to vibration hinders proprioception and influences
quencies of up to 10 Hz, while the frequencies with a the production of finely graded hand-forces. 13,14 Immedi-
deeply molded rope accounted for 18 to 60 Hz. The ately after an exposure to vibration, the responsiveness
ropes differed significantly (p < .001) in frequencies be- of spindles is diminished. The postvibratory depression
tween 20 and 50 Hz. The exposure time of vibration of spindle sensitivity lasts for only a few seconds, but
lasted between 3 and 5 seconds. Conclusion: Consider- the disturbance in proprioception can persist for up to
ing the negative effects associated with vibrations, pru- a few minutes. The interaction between the hands and
15
dence is required when using deeply molded ropes due a vibration releasing tool is influenced by the type and
to the increased vibrations of about 20 Hz. the condition of the tool. For Special Forces, the tool
used to rappel out of a helicopter is a rope. Fast-roping
Keywords: fast-roping, vibrations, motion, rope, sensations, is a rappelling maneuver of civilian and military Special
rappelling, abseiling, vibrations, kinesthetic illusions, Special Forces used to deploy into a location rapidly through
Operation Forces descend out of a helicopter. This technique requires no
individual mechanical hook-up to the rope. Each mem-
ber of the team must wear proper fast-rope gloves when
sliding down the rope to protect against the heat gener-
Introduction
ated by friction. To carry out a fast and safe descent, the
Vibration is defined as oscillatory motion in which the Soldiers grab the rope with both hands and then step
motion is not constant but alternately greater and less out of the helicopter. By opening and closing the hands,
than some average value. The magnitude of vibration is the pressure onto the rope is decreased or increased and
determined by the extent of oscillation, whereas the fre- rappelling velocity is regulated. After the maneuver,
quency of vibration is determined by the repetition rate Special Forces are required to perform a precision task
of the cycles of oscillation. The frequency of vibration is to operate precisely (e.g., aiming and shooting) within
measured in Hertz (Hz) and is the main factor determining a few seconds. For safety, disturbances of the sensory

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