Speed
Speed is a ratio between total distance and total time. To find speed you divide the distance by the time. Speed can be changed by ether adding or subtracting to time or distance. Knowing this if you can hold a higher speed then you will have a lower time. Speed is what make a run have a higher or a lower time then you normally would. Speed can be written as m/s for the metric system or mph for the non-metric system.
Velocity
Velocity is similar to Speed, but velocity is a vector, it has magnitude with direction. Velocity in running is the speed that your running and the direction that your running. Velocity is written similar to speed, but velocity is written with a direction after it. An example for velocity is 25m/s north or 25mph north. Velocity is important to understand because velocity describes how fast you are running and witch direction you are running in.
Acceleration
Acceleration is the change in velocity for an object. When your running acceleration is the most important part. The ability to accelerate, especially in short sprints can make the difference between 1 place and last place. The ability to accelerate to your top speed is vital when it come to getting in front of your opponent. Understanding what acceleration is important to know how to build up your acceleration. When you are execrating you have to over come friction and after you start moving you'll be able to accelerate to top speed faster.
Speed, velocity and acceleration video
The movement in your legs
The way that you move your legs can have a large impact on your speed and your acceleration, it can also affect how much energy you use. When you run you can ether stride out or you can do short steps. When you stride out you are extending your leg witch gives you a farther distance traveled on a single step. Striding out is a good way to cover a larger distance using less energy and getting a faster speed. Strides are commonly used by long distance runners because it uses less energy, and can reach higher speeds that normal. The other kind of run is a short step, these are when you move your feet as fast as possible. Short steps are used more commonly by sprinters because you can get a faster speed in a shorter amount of time. Using short steps uses more energy, but you can reach faster speeds than the strides. The way that you can affect your speed and the energy that you use.