Rapidly moving from one place to another, also known as sprinting, is an action that is required in many different sports and activities. Sprinting can be broken down into four different phases, each distinguishable from the others by comparing three different variables. These variables are stride length, stride frequency and ground contact time.
The initial phase of sprinting is known as the starting block phase, where the sprinter is in contact with the blocks. This phase has the greatest amount of ground contact time, or the total time in which the feet are in contact with the ground or blocks. This is when force production is the greatest. With the rear leg producing force for only 45 percent of the contact time, the front leg is believed to be of more importance at the start. Stride length and stride frequency are not factors in this phase because the sprinter is not moving.
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Once the sprinter takes off from the blocks, they begin to accelerate by increasing stride length and stride frequency. The length of this phase can be anywhere from 30 to 50 meters among top sprinters during a 100-meter race. During acceleration, the time in which the foot is in contact with the ground is relatively long in order to generate high levels of force, but decreases as the sprinter achieves maximum running speed.
Constant Speed Phase
The constant speed phase can be submaximal, maximal or supramaximal and is characterized by both the stride length and stride frequency remaining the same over a period of time. This phase is generally achieved between the 60 to 80 meter mark in men and 50 to 70 meter mark in women. In principle, the top sprinters can sustain this phase over a distance of 10 to 20 meters. The difference between elite and sub-elite sprinters is the frequency of stride, demonstrating that it is more important than the length of the stride.
The last phase is categorized by a decrease in sprinting speed, usually occurring between the 80 and 100-meter mark in top sprinters. Velocity begins to decrease on a scale of .5 to 1.5 meters per second and is caused by central and peripheral fatigue. The decrease in speed is mainly caused by a decrease in stride frequency, as stride length and ground contact time is increased when compared to the third sprinting phase.