If soccer players want to run quickly, then they need to be producing a lot of force against the ground. There are two ways to do this; firstly, we can produce this force via our muscles when our foot is on the floor, or, secondly, we can have our foot moving at a very high speed once it hits the floor. For elite sprinters, it is, of course, a combination of the two. So, ideally, you want to have a large range of motion in which to accelerate the foot towards to ground (requiring good front side mechanics); you want to be able to accelerate the foot downwards (requiring good hip extensor strength); you want to contact the ground in the optimal position (requiring good sprint mechanics), you want to be able to absorb and reuse much of the force you apply (requiring good foot and ankle stiffness), and you want to be able to produce force quickly (requiring an optimal level of strength and power).
Soccer performance demands and development are on the forefront of research these days and within the last year there have been some huge studies. Not every study is done perfectly, but I think when they use large enough sample sizes like they did in the cases below, there is a lot to learn and it would be dumb of me not to use this valuable information to help players and coaches. So, lets get nerdy and dive in to the science.
Many strength coaches in America come from powerlifting backgrounds and Olympic lifting backgrounds, so in this whole get strong to get fast movement, squats, aka the "King of all exercises", were promoted heavily. Not just squats, but DEEEEEEP squats. I began to think that anyone, anywhere, who wasn't shit staining the floor was a phony lifter and definitely not improving much of anything. That is one area where I was flat wrong. And here is a study to prove it: