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

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

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

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

What is a Roundhouse Kick? Explain how to do RHK

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

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

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

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.

Back leg kick

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

Displacement vs. Time

Velocity vs. Time

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= 74.10 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= 61.672 + 41.082 F= (0.7 kg)(74.10 m/s2)= 51.87 N

Calculations: Momentum Momentum: p= mv= 6.314 kg m/s mfoot = 0.7 kg v= 9.02 m/s vy= 7.505 m/s vx= 5.003 m/s v2 = vx2 + vy2

Impulse Impulse: J= F∆t; ∆t= 0.024 sec J= 51.87 N x 0.024 sec= 1.25 Ns J= ∆mv= 1.5309-0.6146= 0.9163 kg m/s t= 1.136 v= 2.187 m/s t= 1.160 v= 0.878 m/s

Energy during Kick Kinetic Energy: ½ mv2 Potential Energy: mgh ½ (0.7 kg) (9.02 m/s) 2= 28.48 J Potential Energy: mgh h= 1.404 m (0.7 kg)(9.8 m/s2)(1.404 m)= 9.63 J Total E: 28.48 J + 9.63 J=38.11 J

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

Vertical Work a= 13.00 m/s2 Wx= Fdx = madx= (0.7)(13.0)(1.404m)= 12.78 J

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

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

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.

clockwise counter-clockwise

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.

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

Sources Boey, L.W. & Xie, Wei. (2008) Experimental Investigation of Turning Kick Performance of Singapore National Taekwondo Players. Journal of Biomechanics, 42(3), 242-248. 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, 31-38. Pearson, Jake. (1997) Kinematics and Kinetics of the Taekwon-Do Turning Kick. Unpublished Bachelor Degree Dissertation, University of Otago.