1. Deborah Yeh Professor Rome BIOL 438 Spring 2012
MECHANICS OF THE
ROUNDHOUSE KICK
Deborah Yeh
Professor Rome
BIOL 438
Spring 2012

2. What is Tae Kwon Do?
Tae Kwon Do: A Korean unarmed martial art distinguished by its emphasis on kicking techniques.
Mainly used for self-defense, but can also be a sport.
Variety of types of kicks
Position
Difficulty level
Combos
There are many forms of martial arts. They can be armed, like kendo

3. Basic Kicks in Tae Kwon Do
1. Front kick--

4. What is a Roundhouse Kick?
Most frequently used kick in TKD
60% of kicks in TKD championship (Pearson, 1997)
Easy to attack from fighting stance
Kicking leg travels in an arc towards the front

5. What is a Roundhouse Kick?
Explain how to do RHK

6. Front View of Roundhouse Kick
there’s displacement in the X, Y, and Z directions

7. Top View of Roundhouse Kick
Final
position
Kicking leg sweeps across 180° from its initial position
Semicircular motion (2 parts)
Lift knee
Extend knee
Extend leg
as you can tell, proper execution of the RHK involves coordination of many different body parts, such as the torso, the hips, the knees, and the ankles.
Lift knee
Initial position

8. Muscles Involved in RHK
Spinal flexors, spinal rotators, Gluteus maximus, Rectus femoris, muscles in the foot

9. Break-down of the RHK Prepare for kick Deliver kick Recovery
Pick up the knee of the kicking leg directly in front of you above waist level. The higher your target, the higher you should raise your knee. Fold your knee tightly. Point your kicking foot and toes downward. Turn the hip over by turning the toes of the supporting foot away from the target. (Do not allow the kicking knee to dip or point downward) At this point the shin and thigh of your kicking leg should be parallel to the floor. Point the chambered knee past your target so that your kick will penetrate past the target’s surface.
Extend your leg to deliver the kick.: Deliver the kick by unfolding the leg at the knee, rotating through the target and snapping the hips over at the moment of impact. The target should be struck at ninety-degree angle before your leg reaches full extension and the kick should be allowed to continue and penetrate several inches past the surface before returning.
Retract your leg.: Retract the leg as quickly as possible by bending the knee tightly. The less time the foot is in contact with the target the more "shock" will be transferred to the target, the longer you foot is contact with the target the more pushing power will be transferred to the target. At this point the leg can return to the chambering position in preparation for a second kick or returned to the floor.

10. Back leg kick

11. Limitations No force plate, cannot accurately measure impulse
No punching bag
Markers were sometimes difficult to see
Cannot account for 3D motion
Describe Z axis qualitatively
Form is not perfect

12. Displacement vs. Time

13. Velocity vs. Time

14. Calculation: Force of Kick
F=mfoota
mfoot = 1.4% of 50 kg= 0.7 kg
Assume that mass of foot is 1.4% body mass
a= m/s2
At peak velocity (t=12.96 s)
Slope for plot of X-velocity vs. time: 61.67
Slope for plot of Y-velocity vs. time: 41.08
a2=
F= (0.7 kg)(74.10 m/s2)= N

15. Calculations: Momentum
Momentum: p= mv= kg m/s
mfoot = 0.7 kg
v= 9.02 m/s
vy= m/s
vx= m/s
v2 = vx2 + vy2

16. Impulse Impulse: J= F∆t; ∆t= 0.024 sec J= 51.87 N x 0.024 sec= 1.25 Ns
J= ∆mv= = kg m/s
t= 1.136
v= m/s
t= 1.160
v= m/s

17. Energy during Kick Kinetic Energy: ½ mv2 Potential Energy: mgh
½ (0.7 kg) (9.02 m/s) 2= J
Potential Energy: mgh
h= m
(0.7 kg)(9.8 m/s2)(1.404 m)= 9.63 J
Total E: J J=38.11 J

18. Horizontal Work
a= m/s2
Wx= Fdx = madx= (0.7)(11.63)(1.064m)= 8.66 J

19. Vertical Work
a= m/s2
Wx= Fdx = madx= (0.7)(13.0)(1.404m)= J

20. Review: Top View of Roundhouse Kick
Final
position
Kicking leg sweeps across 180° from its initial position
Semicircular motion (2 parts)
Lift knee
Extend knee
Displacement of the leg in X, Y, and Z axes
Extend leg
as you can tell, proper execution of the RHK involves coordination of many different body parts, such as the torso, the hips, the knees, and the ankles.
Lift knee
Initial position

21. Angular Velocity ∆θ= 5∏/4 rad ∆t= 1.024 sec ω=3.834 rad/sec
135°

22. Elbow Rotation Rotation of the elbow/arms generates angular momentum.
Conservation of Momentum: Momentum of a closed system remains constant
As arms swing back to original position, the heel of the standing leg rotates, allowing the hips and kicking leg to rotate as well.

23. clockwise
counter-clockwise

24. How to increase impact velocity
Impact velocity = linear distance/time
Increase linear distance traveled by foot while keeping elapsed time the same.
Reducing time while keeping linear distance the same.

25. Future Research Questions
Use program to account for 3D motion
Front leg vs. Back leg kick
Other turning kicks:
Spinning wheel kick
Tornado kick

26. Sources
Boey, L.W. & Xie, Wei. (2008) Experimental Investigation of Turning Kick Performance of Singapore National Taekwondo Players. Journal of Biomechanics, 42(3), Kim, Y.K., Kim, Y.H., & Im, S.J. (2011) Inter-joint coordination in producing kicking velocity of Taekwondo kicks. Journal of Sports Science and Medicine, 10, Pearson, Jake. (1997) Kinematics and Kinetics of the Taekwon-Do Turning Kick. Unpublished Bachelor Degree Dissertation, University of Otago.