3-D INVERSE DYNAMICS ANALYSIS OF MARTIAL ARTS CIRCULAR KICK
1
David Saxby and 2
D. Gordon E. Robertson
School of Human Kinetics, Faculty of Health Science, University of Ottawa, Ottawa, Ontario, Canada
Email: 1
dsaxb037@uottawa.ca, 2
dger@uottawa.ca
INTRODUCTION
This project investigated the kinetics of the lower
limbs during the martial arts circular kick. Patterns
of the net moments of force and powers were
computed three-dimensionally. Due to the lack of
three-dimensional kinetic investigations of the
circular kick, this paper attempted to establish a
basic outline of the recruitment patterns seen in this
particular kick. The kinetic data were compared
with similar powerful kicking activities from the
literature such as soccer kicking [1] and karate front
kicks [2]. Our hypothesis was that the circular kick
requires similar kinetic patterns as other kicking
modalities but possesses distinct features such as
significant abductor power recruitment at the hip,
limited pre-stretch and reduced follow-through.
METHODS
One subject performed a total of 15 trials of the
circular kick delivered with maximal force into a
stationary pad. The subject was an elite-level
combat athlete competing internationally at 80 kg.
A Vicon Motion Analysis system recorded the
trajectories of 42 markers using seven MX-13
cameras at 200 Hz (see Figure 3). The marker
coordinates were filtered using a Butterworth
lowpass digital filter with cutoff of 6 Hz. Two
Kistler force platforms measured the ground
reaction forces of stance and kicking legs. Analog
signals were filtered at 20 Hz. Visual3D computed
the angular velocities, moments and powers for the
ankle, knee and hip of both lower limbs using
inverse dynamics. Only the kicking leg's results
will be reported.
RESULTS AND DISCUSSION
Figure 1 holds the sagittal plane ensemble averaged
(15 trials) angular velocities, moments and powers
of the kicking leg's ankle, knee and hip joints. The
results start 0.43 seconds before pad contact when
some of the markers of the kicking leg become
occluded. Negative values of the angular velocities
and moments of force are plantiflexor at the ankle,
flexor at the knee and extensor at the hip. Positive
powers indicate the rate of work done by the
associated moment of force.
As the kicker begins the kicking motion, the hip
extensors of the kicking limb (H1 in Figure 1) work
positively to extend the hip until toe-off at t=0.28 s.
After slight delays, both the ankle plantiflexors (A1)
and knee flexors (K1) performed positive work to
push away from the floor and simultaneously
actively flex the knee, respectively.
After the leg is in swing (at t=0.28), the hip flexors
acted to flex the hip (H2) and then immediately
before contact the hip extensor moment dominated
to stop hip flexion and extend the knee and foot
towards the pad. In contrast, the knee flexors
transition briefly to eccentric work to prevent
hyperextension of the knee [cf. 2].
Figure 1: Flexor/extensor angular velocities
(top), moments (mid) and powers (bottom) of
ankle (left), knee (mid) and hip (right) of the
kicking leg.
Figure 2: Ab/adductor angular velocities (top),
moments (mid) and powers (bottom) of the hip of
the kicking leg.
Figure 2 holds the frontal plane ensemble averaged
(15 trials) angular velocities, moments and powers
for the hip of the kicking leg. Negative velocities
and moments indicate abduction.
Notice in Figure 2 the abductor moment is initially
acting isometrically. The abductor moment quickly
begins positive work to elevate the kicking limb to
the maximum kicking height. Then, the adductor
moment works eccentrically to stop the elevation of
the limb. Prior to impact, the adductors briefly act
isometrically and then eccentrically to control the
rates of abduction. Note prior to impact, the kicker
is rotating towards the pad on the stance leg. As
well, the trunk is substantially hyperextended as the
kick is delivered.
This circular kick did not exhibit identical
recruitment patterns as soccer kicking or the karate
front kick. The circular kick differs from a soccer
kick because it is delivered from a stationary stance,
has no approach run and has no follow-through. As
well, martial arts kicks are delivered so an opponent
cannot anticipate the time of execution. As result,
the pre-stretch­while it does occur­is not as
dramatic or pronounced as in soccer kicking where
a large wind-up precedes a maximal kick. It appears
being fast and accurate with the circular kick is
more valuable than maximal power. Additionally,
soccer kicks and karate front kicks use different
surfaces for contact with the ball or opponent. In the
circular kick, the athlete uses the anterior surface of
the tibia as the contact surface; whereas, soccer
kicking uses the instep and the karate front kick
uses the ball of the foot. As a result, the knee flexor
moment of the circular kick activates earlier in the
motion to resist extension of the knee and to ensure
that proper contact is made with the pad. This
accounts from the lower hip extensor activity
compared to soccer and karate front kicks.
CONCLUSIONS
The martial arts circular kick exhibited prestretching,
large concentric flexor and extensor hip
powers, large ankle plantiflexor power at push-off,
substantial hip abductor and adductor moments and
powers as well as protective or breaking behavior at
the knee joint. These results demonstrate the martial
arts circular kick has distinctly different kinetic
characteristics than either the soccer kick or the
karate front kick.
REFERENCES
1. Nunome H, et al. Med Sci Sport and Exercise,
34: 2028-2036, 2002.
2. Robertson DGE, Mosher RE. Biomechanics IXB.
Human Kinetics: Champagne, IL, 1985.
Figure 3: Model immediately before impact.