When you throw an object you need to apply the largest force to it
for the longest possible time. The physiology of the body will affect the largest force that can
be usefully applied. The length of time during which the force is applied can be increased by
bringing your arm back during the throw and following through with your leg during a
kick.
A javelin thrower or shot putter will always throw the javelin starting with their
arm well behind their body. This is to give the maximum time for the force to act on the
javelin before release.
An interesting case is where you are firing or throwing
nothing – e.g. a bow is bulled back under tension and then released with no arrow being
fired. There is a danger of breaking the bow since all the energy stored in the stretched string
goes into the motion of the bow.
You can also test this by throwing a ball and then
doing the throwing action again but this time without a ball in your hand – it hurts your arm as
all the stored energy must be absorbed by your arm again in bringing it to rest.