When thinking about running speed, it becomes obvious that there are two components.
One is how fast the legs are switching, that is, stride rate (also known as cadence). The other is how long each step travels, that is, stride length.
Everything else that a runner does, such as posture, upper body movement, breathing, etc. are all meant to increase either stride rate or stride length, thereby increasing the speed.
Now then the how-to-run-faster question becomes a multiple-choice problem. To increase the speed, a runner can either
- Increase the stride rate,
- Increase the stride length, or
- Increase both
From my reading of discussion threads and blog articles, there are many debates among runners regarding optimal stride rate. There are several articles that seem to suggest that optimal stride rate is 90 strides per minute (180 steps per min). Does that mean if I were to increase my speed, I have to increase my stride length?
Let’s figure it out by analyzing my own interval training data, where I vary my running speed.
How am I varying my speed? Is it by controlling stride rate, or stride length, or both?
Thanks to my stride sensor, I have the following data from my interval training the other day.
Red line is showing the stride rate (cadence) on the left Y axis, and purple line is showing stride length on the right Y axis. What’s interesting is that as I increased my running speed, I increased both stride rate and stride length. (This was done on a treadmill while controlling the speed. I remember the initial speed was at 6 miles/hr, and I jumped to 10 miles/hr. If you do the math, you’ll notice that my stride sensor was reporting my speed a bit lower. I’ll talk more about that later.)
When I increased the speed from 10 to 10.5 miles/hr toward the end (two wider peaks), I was increasing stride rate instead of stride length on the top end of the speed.
On the lower end of speed, when I slowed down to 4 miles/hr walking pace around the last two peaks, I was modulating my stride rate while keeping my stride length constant. This meant that my jogging (about 6 miles/hr) stride length is just about the same as my walking (about 4 miles/hr) stride length. What accounted for slower speed was my stride rate, which dropped from mid-80’s to low-60’s.
This is easier to see when stride rate is plotted against the speed.
In the above graph, the X axis is showing the stride rate (cadence), the Y axis is showing the speed, and the color of each circle is showing the stride length, where the darker the color, the longer the stride length is.
Most of my interval running had the stride rate between 85 and 95. And the speed within this stride rate zone was primarily controlled by stride length.
This shows I’m using my stride rate to vary my speed at the lower end, and primarily using the longer strides to pick up speed at the higher end. But in the very top end, I tend to rely on stride rate to increase the speed even further.
If I were to plot out these three phases, they would look like the following.
Yellow is the walking to jogging where I’m varying stride rate with minimum stride length. Orange is the jogging to running where both stride length and stride rate are increasing. Red is the final phase where stride length is staying constant yet stride rate is increasing by a bit.
It is interesting that increasing stride rate is where I can gain the last bit of speed. Reading about how a professional runner used higher stride rate in the home stretch to win a race, I somehow feel validated.