Sa. Lynch et al., ELECTROMYOGRAPHIC LATENCY CHANGES IN THE ANKLE MUSCULATURE DURING INVERSION MOMENTS, American journal of sports medicine, 24(3), 1996, pp. 362-369
Ten uninjured subjects (ages 18 to 30 years) had electromyographic tes
ting of the peroneus longus, peroneus brevis, and tibialis anterior mu
scles in response to inversion moments at two speeds (50 and 200 deg/s
ec) and two joint angles (neutral and 20 degrees of plantar flexion) u
sing a hydraulically controlled tilt platform. Subjects underwent 10 t
rials of each type of inversion moment on Day 1 testing, which include
d both legs. On Day 2, subjects again underwent 10 trials of each type
of inversion moment, but only on one leg. Reliability was assessed by
comparing left and right leg data within muscle groups for Day 1 test
ing. Repeatability was assessed by comparing Day 1 with Day 2 data. Th
e latency measurements (the time between the beginning of the inversio
n moment and the onset of first motor response) for the peroneus brevi
s and tibialis anterior muscles were found to be reliable and repeatab
le with no significant differences between the same muscle groups. The
peroneus longus muscle had a significant difference between legs but
was found to be highly repeatable. Speed of inversion moment and plant
ar flexion angle both caused significant changes in latency response o
f the peroneus muscles, with increased speed producing a shorter laten
cy response and increased angle causing a longer latency response. Our
results indicate a loss of protective reflexes with increasing planta
r flexion.