How can I improve my speed?

Running alone will not help, Running only works on endurance, You need to incorporate exercises that utilize STATIC muscle reaction to help out with Exploding off the line, Try any Plyometric routine or just do distance sprints varying in distance but not over 70-80 yards

You don't need to be able to put your leg behind your head to improve your speed. It helps that your muscles can move and recover after being used going through a traumatic few seconds. You are asking your muscles to do amazing things in short intense periods, make sure your muscles are warmed up, some stretching before practices and races, you do not want your muscles too long that's why you see sprinters are usually well muscled, tight and compact like in comparison to a distance, as a hurdler, high jumper, long jumper etc it helps to be flexible to a point as you are putting your muscles in different configurations. I would say flexibility helps and affects speed in a minimal way the thing you should really be concentrating on is technique and power to improve your speed.

Start running down hill. Your legs will have to move faster or you will trip and fall on your face. This will create muscle memory and will translate to level ground after a few months of practice.

I hear running hills improves your speed :D

1.jump rope "the boxers do this to build speed"

2.treadmill

3.biking

4.running from dogs

5. stop eating cake,donuts,muffins junk food.

6.sit ups /crunches

Wind sprints while wearing a drogue chute behind you.

Basically, you cannot increase your speed. It is a hereditary factor in your makeup. Do you think the football stars are the product of hard work or natural talent? Clue: it ain't hard work.

Start smoking.

parachute