PHASE THREE- GUN

The gun phase of the block start is a reflex action to the fire of the gun. In biomechanical terms it is the moment of force as inertia is overcome to accelerate from a station position. The movement is as follows (fig 4.1, 4.2);

1. Feet drive off blocks- front leg pushes off block extending to provide drive, back leg is pulled through bent and low prepared fro first stride.
2. Arms lift off ground, begin rapid running motion
3. Drive is forward not upward
4. Head remains in line with body and looking at the track

(Ballesteros 1979, Rice 2000)

Picture sources 23-4-13- http://digitaltrackandfield.com/starting-blocks-for-sprinters/

Biomechanical Principles

This is an explosive movement that quickly gains momentum from stationary position pushing away from the force of blocks in the ground. This is achieved by Newtons second law ‘The acceleration of an object is proportional to the net force acting on it and inversely proportional to the mass of the object’. As the athlete wants to change the state of motion force needs to be applied, therefore they need to push off the blocks with great force. Next Newton’s third law can be applied as ‘For every action there is an equal and opposite reaction’. As the athlete pushes off the blocks, the blocks cling to the ground and push back against the athlete’s strides to created forward motion and kinetic energy (Blazevich 2010 p42). 

As an imbalance is also created in the set position this initial movement is a falling action that is overcome by short fast strides accompanied by fast arm movements. Newton’s third law is also connected to the coupled movement of arms and legs in the block start. As the legs begin to cycle and the arms swing in an arc, with the right arm singing forward as the left leg strides in front, and visa versa. The torque created by the legs pushing forward off the ground and the angular momentum from the arms balances this movement. As the stride length extends out of the start so should the arm swing (Blazevich 2010, p94)