The reason athletes are slow, in most cases, is because they are weak relative to their body weight. Slow athletes have a low strength to body weight ratio, while fast/explosive athletes have a high strength to weight ratio. How much force you are able to create against the ground relative to your body mass when sprinting, determines how fast you move in the desired direction.
As an example:
Athlete A can deadlift 275 pounds and weighs 190 pounds: Strength/weight ratio - 1.45
Athlete B can deadlift 275 pounds and weighs 160 pounds: Strength/weight ratio - 1.72
Both athletes are capable of applying the same amount of force, yet you can almost guarantee that athlete B will be the faster of the two assuming similar running form. This is because his strength to weight ratio is higher, which allows him to apply more force into the ground relative to his size. I see this constantly when I am training athletes. Faster athletes lifting the same amount of weight as the slower athletes who are 30-40lbs heavier than them. I would invite anyone to attend one of our training sessions to see this first hand.
A big misconception when it comes to speed training is that ladder drills, plyometrics, and other various agility drills are the solution to the problem. The truth is that yes, those things will help and yes you should do them, but only as a supplement to your strength training program. If you really want to get faster, then 75% of your speed training should be based around developing strength.
How do you go about doing this?
Lift heavy weights, particularly the hex bar deadlift, squats (back/front/box/split squats) and Romanian dead lifts. In addition to this, you will want to do extra work on the glutes and hamstrings. Reverse hypers, hamstring curl machines, glute bridges, and the glute/ham machine are great examples of this. In order to get stronger, we need to force the body into recruiting the largest motor units possible when training. This is accomplished most efficiently by lifting heavy weights for lower reps. Stick with a 5 sets of 5 protocol or 5 sets of 3 with adequate rest in between sets (see my article titled "How to lift like an athlete" for more on this).
Develop the horsepower in the weightroom first, then fine tune it out on the field later, but not until the horsepower is there. I would bet on the athlete with a higher strength to weight ratio ten out of ten times over the athlete with better running form in a race. This is why we focus so heavily on the strength component when we train our athletes at Performance U. Simply put, it is the most efficient use of our training time to accomplish the desired result of being a more powerful and explosive athlete.
If you want to get faster, start by getting stronger.
The video below shows a great example. Saquon Barkley, the running back from Penn State is the current Heisman Trophy front runner and the fastest human you have ever seen. At 220lbs he is shown squatting 495 for 7. His strength to weight ratio must be infinity.