Who is the fastest football player in the world? Messi? Or Cristiano Ronaldo? Both are a great player. We all know that but now I want to discuss who is the fastest man in football(currently active) and unfortunately, it is not Messi and Ronaldo. To be clear, there is a test that relies on speed and not related to skill or etc. In 2014, FIFA has been conducted a test which determined that Arjen Robben is the fastest sprinter in the world as he clocked 37 km/h.source
How did he run so fast? Here is the explanation :
During running, force plays an important role to the runner. Here is the force that involved during running
The picture shows the force that involves during running. The F(x) is the force acting at the x-axis which known as the propulsion forces. Then the F (y) is the force that acts due to the contact between the foot and the ground. The F(g) is the force acted due to the gravity which lies on the y-axis. The F(g) is located at the center of the mass of an object.
The force that relates to the speed while running is on the x-axis. F(x) is applied by the muscles for a forward motion causing acceleration. The opposite of the force is the frictional force. At a full sprint, for the F(x) propulsion force, an average person can apply 500-600 pounds of total peak force but an Olympic sprinter can apply more than 1,000 pounds of force.sourceThe force make him move forward so fast.
By using or understanding the force they can take an advantage to accelerate faster. They used the gravity which they lean forward to make it work for them. That is why we never saw an athlete run with a straight body posture. Then, the arm swinging which stabilizes the body while running. Arm swinging also can affect the speed. After that, an athlete has to understand the surface of the ground(friction), where they can apply the right shoes.
In conclusion, the thing that affects the speed while running depends on individual skill, technique and training. If we just know the theory but lack of training and did not work hard to achieve it, it is useless.
Reference :
1.Fastest footballer in the World 2018!
3.Usain Bolt: Case Study In Science Of Sprinting
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Disclaimer: I am not an expert. I wrote based on my understanding and my experience. Maybe some of it is not accurate from the fact. If I make something wrong, feel free to drop a comment.