Biomechanics of throwing a frisbee Daniel Kim Biology 438-301 Professor Rome

Once upon a time… Wham-O Toys Bridgeport, CT – William Russell Frisbie opened Frisbie’s Pie Company Cotroneo analysed biomechanic and aerodynamic aspects of disc flight from throw observations. Release velocities were correlated with range to confclude that initial velocity is the most important factor affecting the maximum distance thrown

Frisbee Throws Backhand Forehand Overhead Standard Skipping Hover Curve Pass Forehand Overhead All work under a similar principle

3 Stages of a Frisbee Throw Wind-up Acceleration Follow through

Range of Motion Cotroneo (1980) compared the force contribution of body segments in backhand versus forehand Frisbee throws while The segments of the torso and throwing arm act as a kinetic chain to maximize the speed of the final segment. Cotroneo concluded that there is a relationships between initial velocity and maximum distance thrown Controneo analysed biomechanic and aerodynamic aspects of disc flight from throw observations. Release velocities were correlated with range to conclude that initial elocity is the most important factor affecting the maximum distance thrown.

The Backhand Throw

Backhand Throw

Wind Up (backhand) Torso twists (winding up) Weight of thrower shifts to left foot Arm horizontally adducts towards torso Forearm flexes Wrist curls Analysis of 57% maximal effort throws reveals that the largest power contribution results from horizontal adduction of the shoulder providing nearly all the work done to increase translational velocity of the Frisbee.

Acceleration Continues from maximum rotation of torso Sequential uncoiling of torso and arm Torso twists right and bends forward Weight shifts to right foot Humerus and torso are aligned Forearm pronates All-important wrist flick

Follow Through Arm continues to extend at shoulder, elbow, and wrist Finished when torso twists maximally to the right

Second Look at the Backhand

Second Look at the Backhand

X-Displacement vs. Time

Force Generated and Work Performed Assuming that mass of a human arm is about 6.5% of total body weight: marm= 73 kg*.065 = 4.75 kg Acceleration prior to release was 22.65 m/s^2 Force = Mass * Acceleration 4.75 kg * 22.65 m/s^2 = 107.6 N Work = Force * Distance Distance traveled: 1.412 m 107.6 N * 1.412 m = 152 J Velocity from logger pro (calculated in quadrature): 13.1 m/s

The Forehand Throw

Forehand Throw

Wind Up Feet facing receiver Knees slightly bent Weight shifted to right foot Torso turns right (winding up) Shoulder horizontally abducts away from torso Elbow pointing forward saFeet facing receiver Knees slightly bend Weight shifted to right foot Disc brought back Elbow pointing forward Shoulder begins snap Torso unwinds first Then Shoulders Then Elbows Then WRist df

Acceleration and Follow Through Torso unwinds Shoulders rotate giving speed Elbows straighten Wrist snaps Throw completed when torso is facing forward

Second Look at the Forearm Throw

Second Look at the Forearm Throw

X-Displacement vs. Time

Force Generated and Work Performed Assuming that mass of a human arm is about 6.5% of total body weight: marm= 73 kg*.065 = 4.75 kg Acceleration prior to release was 23.97 m/s^2 Force = Mass * Acceleration4.75 kg * 23.97 m/s^2 = 114 N Work = Force * Distance Distance traveled: .8594 m 114 N * .8594 m = 100.0 J Velocity from logger pro (calculated in quadrature): 12.3 m/s

Conclusions Compare energy inputted to the velocity of the frisbee to see which throw is more energy efficient Backhand Throw: 152 J / 13.1m/s = 11.60 Forehand Throw: 100 J / 12.3 m/s = 8.13 Given this single trial, the backhand form requires more energy than the forehand form.

Future Investigation Using different camera angles, calculate the energy inputted as rotational energy. Which throw puts more spin into the frisbee? Investigate the specific backhand throws (skipping, hover, curve pass) and analyze how the body inputs the proper energy to manipulate the trajectory of the frisbee.

Resources http://morleyfielddgc.files.wordpress.com/2009/04/hum melthesis.pdf