| The purpose of the research was to study the repeatability of
electromyographic (EMG) waveforms of major lower limb muscles during
the naeryo chagi (axe kick) in taekwondo. Six male and female athletes,
aged between 20 and 24 years served as volunteers. All participants
were black belt holders and performed the naeryo chagi with their
right leg. The electromyographic activity of rectus femoris, biceps
femoris, gastrocnemius lateralis and tibialis anterior was recorded
during the kick through four preamplified surface electrodes. The
participants preformed 10 successive kicks to a fixed target with
1 min inter-trial interval. The electromyograms were recorded during
each kick at a sampling frequency of 1000Hz. After the processing
of the raw EMG data, myoelectrical activity was normalized on the
time and amplitude domain. The coefficient of variation (CV), intra-class
correlation coefficient (ICC) and coefficient of multiple correlation
(CMC) were computed to test the repeatability of the electromyographic
waveforms in each participant. The electromyographic activity during
the naeryo chagi demonstrated poor repeatability. More specifically,
all CVs were greater than 80%, all CMCs were lower than 0.75 and the
majority of the average measure ICCs as well as all single measure
ICCs were lower than 0.55. It seemed that only ensemble averages of
EMG waveforms obtained from more than ten kicks may be considered
as representatives of the muscle function in naeryo chagi and conclusions
that have been drawn from a single trial should be reconsidered.
KEY
WORDS: Electromyography, reliability, axe kick, taekwondo.
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