The Biomechanics behind Soccer Throw-Ins By: Omar Khan

Purpose To understand the biomechanics behind different styles of throw-ins. To see the relative contributions of different muscle groups to the force generated from a throw-in. To determine whether or not a full-motion throw-in is worth the effort or not.

Why Throw-Ins? They are a very important part of soccer, despite having to use hands. Having a good thrower can become a huge advantage for your team. I’m weak…

Different types of Throw-In Purely Arm Throw-in Arched Back Throw-in Run-up Throw-In Flip Throw-In

Arm Throw-In

Arm Throw-In: Muscles involved

Fast-twitch muscle fibers Generate significant amount of power

Kinematics: Arm Throw-In Tan-1(1/1.2)= 39.81˚ 13.8 m assuming constant velocity (windy day)

Divide by 10 on the values

Force: Arm Throw-In F=ma Mass of 2 Arms= 8.20 kg Mass of Ball= 0.42 kg

Arched-Back Throw-In

Arched-Back Throw-In: Muscles Involved Erector Spinae

Back Throw-In, Position (Ball)

Kinematics: Arched Back Throw-In Tan-1(1.8/2.0)= 42.0˚ Distance Travelled: 20.67 m

Forces: Arched-Back Throw-In Mass of 2 Arms= 8.20 kg Mass of Ball= 0.42 kg Mass of Torso= 36.81 kg (Assume 45% of body mass) (20.94)(8.62)= 180.5N (2.645)(36.81)=97.4N Total Force= 277.9 N

Run-up Throw-In

Components of Run-up Throw-In Momentum Generating Steps Skip step Stride Jump step Force Generating Steps Lunge Arched-Back Arm motion

Run-Up Throw-In: Muscles Involved

Kinematics: Run-up Throw-In Tan-1(2.0/2.0)= 45.0˚ 25.8 m assuming constant velocity (windy day)

Force: Run-Up Throw-In Mass of 2 Arms= 8.20 kg Mass of Ball= 0.42 kg Mass of Torso= 36.81 kg (Assume 45% of body mass) Mass of Body= 81.8 kg (24.4)(8.62)=210.328N

Force cont. (6.75)(36.81)= 248.468N Total force= 458.8 N

gurrilla

Impulse: Run-up Throw-In Momentum in x direction= mv (81.8)(2.493)= 203.9 ∆Momentum= impulse 0-203.9 =-203.9 N*s Momentum in y direction= mv (81.8)(-1.080)=-88.3 0-(-88.3)=88.3 N*s (this process occurs over 0.6s) Force applied by legs= 339.833 N Force gained by legs=147.167 N Conservation of momentum= 487N close to predicted 457N

Is it worth it? 277-211=66 20.67-13.8=6.87 66/6.87=9.61 N/m 472-277=195 25.8-20.67=5.13 195/5.13=38.0 N/m Not worth it

Further Questions What injuries can arise from over-straining in throw-ins? What are the consequences of raising your back leg in a throw-in? How much force can be generated with a flip-throw-in? What is the ideal angle for the trajectory of the ball? How can we limit the assumptions made for this project? Further studying the projectile motion of the ball. How does hand positioning affect ball movement?

Flip Throw-In

References http://brennanbehindtheline.blogspot.com/