Journal of Applied Physiology, Vol 46, Issue 6 1119-1121, Copyright © 1979 by American Physiological Society
Acceleration forces at eye level experienced with rotation on the horizontal bar
G. R. Beck, P. Rabinovitch and A. C. Brown
Negative acceleration forces (-Gz) experienced at eye level have been
associated with preretinal hemorrhage and headache. These signs and
symptoms were found in individuals who experienced negative (toward the
head) force while rotating on a horizontal bar or hanging from a trapeze.
Lightweight accelerometers were used to measure -Gz experienced at eye
level in children and adult gymnasts performing a single-knee backswing on
a horizontal bar. Rate of onset of -Gz, peak -Gz, time experiencing -Gz,
area of curve (G.second), and mean force (area/time) were calculated. There
was no significant difference between the children and the adult gymnasts
in any of the above parameters. The best gymnast had a maximum rate of
onset of 38.15 G/s and the maximum negative force experienced was 5.52 G.
The maximum rate of onset for a child was 41.56 G/s and the maximum
negative force experienced was 5.73 G. Compared with -Gz tolerance curves
generated on a centrifuge the best gymnast would have become symptomatic
while performing this maneuver in 6 s. The best child would have become
symptomatic in 25 s. These tolerance limits can be easily exceeded by
gymnasts and by the monkey-bar enthusiast.
