This article was originally posted by Ryan at the original HillRunner.com Blogs.
This guy has both parts of the equation covered
Some time ago, I heard a very good coach who I greatly respect say there are three factors that go into speed. Stride length, stride rate, and ground contact time. I’ve heard a lot of similar comments from other runners and coaches.
I’m sorry and it pains me to say this about some people who I greatly respect but they are wrong. It’s even more simple. Speed, if we’re going to look at the pure mechanics of it, is simply based on two factors: stride length and stride rate.
In physics, we learn that speed is distance covered divided by the time it takes to cover that distance. A very straightforward equation, the kind I like.
In physics: Speed = distance / time
To apply that formula to running speed, we get a likewise simple equation: Speed is stride length (distance covered) times stride rate (1 / the time it takes to cover the distance).
In running: Speed = stride length * stride rate
What about the other factors?
What about those other things, such as ground contact time? Those things definitely matter but they are components of the two key aspects of speed. A lower ground contact time or less time spent in the air will lead to a faster stride rate as long as one doesn’t negatively affect the other. Covering more distance while in the air increases your stride length as long as it doesn’t mean you’re covering less distance while on the ground.
Why does this matter?
It matters because it helps us wrap our minds around things if we start at the highest level. If I want to run faster, I need to either take longer steps or take them more quickly. In addition, taking steps more quickly doesn’t necessarily help me run faster if they become shorter and longer steps don’t necessarily help if they are taken more slowly.
If we add other factors that are components of these two factors, we can overemphasize one factor to the detriment of the other. For example, if we say the three factors are stride rate, stride length, and ground contact time, we might focus more on improving our stride rate to the detriment of improving or maintaining our stride length.
Which is more important?
BOTH! Seriously, both are equally important.
Possibly without even realizing, we often see people focus on one to the detriment of the other. We’ve probably all seen the long striders, really working to extend the distance they cover with one step essentially by bounding. The problem is they slow their stride rates often by an amount that causes them to slow overall, even with the longer stride length.
Likewise, I once had a long discussion with a runner who wanted to improve his 800 meter time. Somewhere, he had heard that world record holder David Rudisha ran with a stride rate of 220 steps per minute so he thought that was optimal and tried to match that. He couldn’t understand why his repeats slowed when he ran at 220 steps per minute. The reason was because he was trying to take his steps so quickly that he was shuffling. If Rudisha was really running at 220 steps per minute, which I’m not fully certain of, he had the power to deliver an incredible force to the ground in an astoundingly rapid rate so he could take long steps while doing that. If we consider his world record of just under 1:41 and simplify our assumptions to make the math easy, we would come to the conclusion that he took roughly 370 steps to cover 800 meters. With some rounding error, that’s roughly 7 feet per step.
So what do I do with this information?
Good question. Over my next two Thursday posts, I’m going to cover what we can do to improve each part of the equation. Next week, I’ll focus on stride length. The following week, I’ll focus on stride rate.
In the end, though, we also have to remember that, for the distance runner, the most important factors are fitness and efficiency. If you expend too much energy on either or both of these factors, you can’t make it to the finish line. It’s still good to know about these factors so we can try to improve them efficiently. However, in the end, your fitness and efficiency are the biggest factors in how fast you will run at your next race.
Note: This is part 1 of a 3 part series:
Part 1: Speed = stride length * stride rate. Period.
Part 2: Improving stride length
Part 3: Improving stride rate