The Physics of Javelin Throwing

How to Make the Javelin Fly Far 101

• Maximize release velocity

• Maximize the aerodynamic efficiencies of the javelin

• Maximize the height of release without compromising the first two items

Qualities of the Javelin and How They Affect Flight

The Evolution of Javelin Design

Matti Jarvin - 1932

And Then Came the Scientific Application of Bernoulli’s Principle

• Bernoulli's Principle states increased air velocity produces decreased pressure on the top of an airfoil (top)

• Lift is produced by an airfoil through a combination of this decreased pressure above the airfoil and increased pressure beneath it (bottom)

Credits - AVStop Magazine Online, Helicopter Handbook

1986 Rule Change2011-2012 NCAA Rule Book

Maximizing Aerodynamic GainesRelease velocity and aerodynamic efficiency are not correlated. Therefore, additional distance can be gained independent of release speed by maximizing aerodynamic efficiency.

Aerodynamic gains are achieved by increasing lift and decreasing drag simultaneously

Optimizing Release AnglesThe javelin’s vertical orientation angle describes the angle of the

javelin in relation to the ground. The angle of attack is the angle between

the release speed the vertical orientation angle of the javelin

The javelin’s horizontal orientation angle describes the direction of the

javelin to the left or right. The angle of sideslip is the angle between the

release speed and javelin’s horizontal orientation.

Optimizing Release Angles

Creating Lift By utilizing a negative horizontal javelin angle and adding a slight negative sideslip angle in combination with a clockwise rotation about the javelin shaft, additional lift can be created. The rotation of the javelin causes air hitting the side of the javelin to increase the air flow over the top of the javelin, decreasing air pressure, and creating lift as described in Bernoulli's Principle.

Decreasing DragA small angle of attack reduces the surface area exposed to the air. A throw with a 0 degree angle of attack creates 10 times less drag than a javelin thrown with a 10 degree angle of attack. If all other variables remain consistent, this translates to a 7 meter difference in the throw’s distance.

Similarly, increasing

sideslip angles also increases

drag.

Decreasing Drag

Rotation about the long axis of a javelin can also reduce drag. Just as the spinning wheels of a bicycle keep it from tipping side to side, thespinning of the javelin

around the long axis helps it to resist forward rotation. The spinning of the javelin also stabilizes the vibration in the shaft similarly to how the rifling of a gun stabilizes the bullet.

Decreasing Drag

Angular Velocities and Aerodynamics

Angular velocity about the center of mass in the vertical plane (forward rotation) should be no greater than 9 degrees per second. Rotation faster than this, cancels out gains due to lift. A throw rotating at 18 degrees per second will result in a throw roughly 25m less than a throw rotating under 9 degrees per second.

Angle of attack also affects angular velocity. A positive angle of attack creates drag on the underside of the tail and will cause the javelin to pitch forward. A negative angle of attack creates drag on the top side of the nose and will not cause the same pitching reaction.

Angular Velocities and Aerodynamics

Angular Velocities and Aerodynamics

The trunk tilt angle represents the lean of the torso relative to

true vertical. It describes the

orientation of the trunk, the line of the

hips and the shoulders.

An excessive trunk tilt angle will result in an increase in angular velocity

Trunk Tilt Angle

Drills that address excessive angular velocity in the vertical plane due to trunk

tilt by setting up an effective block:1) Sprint drills to promote good running posture2) Transition Drill to set up good posture in the cross

overs3) Special Strength Drills for the C Position (Square

throws, Three Step Tire Drills, Static Holds)4) Staggered Square Drills to promote proper hip

position in the block

Angular Velocities and Aerodynamics

Angular Velocities and Aerodynamics

Similarly, angular velocities in the horizontal plane

also effect aerodynamic

efficiencies. The greater the

horizontal rotation, the faster the angle

of sideslip will increase.

Christian Nicolay

Drills to address excessive angular velocities in the horizontal plane do to

shoulder Rotation:

1) Pullie Drill2) Poll Drill3) Basketball Throws4) Reverse Pulls

Angular Velocities and Aerodynamics

Maximizing Release Velocity

Release velocity is directly correlated to a throw’s distance. There is both a horizontal and vertical component to release velocity. Because humans

are far more efficient at creating horizontal speed, vertical speed

should only be increased so long as the horizontal component isn’t

diminished.

Technical Elements Affecting Release VelocityTemporal Rhythm

1. Time of throwing procedure (time from contact of the last right foot to release)

2. Time of the single support phase (time spent on the last right foot until the left foot hits)

3. Time of the delivery phase (time from left foot contact to release)

Technical Elements Affecting Release Velocity

Maintenance of Runway Speed Through the Throwing Procedure

Jan Zelezny

Drills that Address Inefficient Maintenance of Runway Speed:

1) Running Mechanics to address posture in the carry and transition phases of the throw

2) Crossover drills addressing posture and stride length, and footfall frequency

3) Right foot action (Soft Step): One step off a low box, 3 step off a low box, down hill throws

Technical Elements Affecting Release Velocity

Technical Elements Affecting Release Velocity

Left Lower Extremity Angles1. Left knee flexion angle - left leg should be

straight at during the delivery phase

2. Left leg angle – the angle should increase in the delivery phase

Technical Elements Affecting Release Velocity

Hip Shoulder Separation

Hip shoulder separation represents trunk twist. Trunk twist is used to convert linear motion to rotational. It can also be very effective in increasing the speed of each body segment in order away from the trunk out to the javelin in a whipping motion.

Technical Elements Affecting Release Velocity

Efficient Summation of Joint Speeds: the Whipping Action

Drills Addressing Efficient Summation of Joint Speeds:

1) Hip activation drill series (low, mid and high positions)

2) Leverage drills (double arm wall drill, single arm wall drill, alternate wall drill, one or two hand square throws with medicine ball, turbo javelin, or javelin)

Technical Elements Affecting Release Velocity

Additional Elements Affecting Distance

1. Height of Release - as high as possible without reducing speed

2. Angle of Release – between 29 and 35 degrees to maximize speed of release and lift.

Tom Petronoff

Special Thanks To:

Steve Leigh, M.S.And

Bing Yu, Ph.D.

Center for Human Movement ScienceDivision of Physical Therapy

The University of North Carolina at Chapel Hill

Under the USATF Scientific Services ProjectFor providing the biomechanical analysis of the javelin throw

cited in this presentation.