Many athletic people all the way from high school all the way up to the professional level tend to ignore some very important muscles that will help with your running speed. A lot athletes tend to think that working out the muscles all over your body will aid in improving your running speed. What really happens most of the time though, is that you overwork certain muscles and don’t work out your hip flexors enough, those muscles are responsible for your stride, the very thing that will improve your running speed.
“ALL plyometric exercises do the same thing: box jumps, bounding exercises, steps, medicine ball workouts, etc. all target the same muscles except they add the element of motion to them”