Abstract
The peroneal reflex time to sudden ankle inversion and the postural control of 15
athletes with functionally instable ankles were compared with 15 stable controls.
A trapdoor produced sudden ankle inversion. Surface electrodes recorded electromyographic
activity of the peroneal muscles. Postural sway was expressed by a transverse sway
value obtained during single limb stance on a force plate. Increased postural sway
was found in subjects with functional instability (p < 0.01). This is in accordance
with previous studies. Functionally instable subjects also displayed an increased
peroneal reaction time (p < 0.01) supporting the theory that functional instability
is induced by a proprioceptive reflex defect. Nine of the 15 instable subjects were
unilaterally instable and showed lower peroneal reaction time and postural sway values
for the stable ankle, but the difference was not significant. There was a high degree
of correlation between postural sway and peroneal reaction time (Spearman's rho =.92).
In ten functionally instable athletes tested with and without ankle taping, it could
not be verified that a reflex enhancing effect of taping occurs through stimulation
of cutaneous afferents.
Key words
Ankle - EMG - postural stability - peroneus muscles
