It’s been widely theorized for a while now that a runner’s ability to extend his/her hips powerfully is the most important factor in determining sprinting speed. High hip extension velocities have been shown to be correlated with greater running speed, and the force produced by the hip extensors have been shown to increase with higher running speeds, so it stands to reason that training your hip extensors to put MORE force into the ground at a FASTER rate will make you run faster.
If you train with me, or you are a regular visitor to this site, you already know that I talk a lot about the importance of hip extension during sprinting. Powerful extension of the hip is what propels runners forward, so my athletes spend a lot of time developing their glutes, which control hip extension. However, one important aspect of our training that I haven’t talked much about yet is hamstring strength. If your hamstring strength isn’t up to snuff, all the glute strength in the world won’t help you run fast.
When sprinting, your goal should be to put as much force into the ground as possible to move forward as quickly as possible. This action is driven by hip extension, but in order for the force generated by the hip to reach the ground, it needs to travel through the hamstrings first. This means that in order to run fast, sprinters need to have strong hamstrings that are capable of absorbing and transmitting huge amounts of force effectively and without injury.
Andrew Sacks Sports Performance 