ACCELERATION FORCES AT EYE LEVEL EXPERIENCED WITH ROTATION ON THE HORIZONTAL BAR

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.cntdot.s), and mean force (area/time) were calculated. There was no significant difference between the children and the adult gymnasts 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.