In sports and exercise, we are often concerned with an outcome resulting from forces acting over a duration of time.

For example, a javelin thrower aims to propel this object as far as possible. At rest, a javelin does not move. In order for the javelin to move, we must apply an impulse.

Impulse, is a product of the force applied to an object or body, and the duration it is applied for. A larger impulse can be achieved by applying a greater force, or applying force for a longer duration. 

A successful javelin thrower has a good technique and range of motion, which allows them to apply forces over a larger angle and therefore, for a longer duration. They are also able to apply large forces in a whip-like transfer of energy through their kinetic chain. 

A summation of forces begins at the ground and work their way up through the hip, shoulder and elbow, into the javelin. 

Momentum is the quantity of motion an object possess and is a product of its mass and velocity. At rest, a javelin has no momentum and because its mass is constant, in order to change its momentum, its velocity must change.

There is a very strong relationship between the distance a javelin is thrown and its velocity at release. Increasing the momentum of the javelin is achieved by increasing its velocity. Faster velocities result from a larger impulse which can be achieved by transferring greater forces through the body over a wider range of motion and therefore a longer duration. 

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