The two dimensions of running speed

Sample combinations

Today's run (street): 3.4 miles

I was looking at the metrics of today's run on Garmin Connect and thinking about the factors that determine pace. I recently put a new battery into my foot pod so I can capture my cadence as well as time, pace, heart rate and elevation. Besides steps per minute (SPM), the foot pod also shows average stride length. After looking at new and past data, I'm seeing some correlation to pace.

When you think about it, running speed is controlled by two factors -- how far you are propelled with each step and the frequency of these steps. As an example, last year I ran the Hot Chocolate 5K averaging 178 SPM, but with an average stride length of 1.03 meters. That translated to an 8:46 pace. A month later I did the LIRCC Hangover Run averaging 172 SPM and .95 meter stride length and averaged 9:50. Fairly small differences translated into almost a minute difference in pace.

Interestingly, my data shows when I run intervals, my stride length drops to half a meter. However, average cadence jumps up to 188. That usually results in an 8:00 pace or better. I've read that, to improve performance, increasing cadence is a better approach than increasing stride length. I'm sure that's due to the danger of over striding which can put excessive pressure on the knees, tendons and ligaments.

Today both my cadence and stride length were middling and I ended up pacing in the mid 10's. That was by design as I wanted to minimize wear and tear on the muscles that may be aggravating my sciatica. Once I'm past this annoyance I'll start playing more with cadence and will try to make my way to the ideal (180 SPM). I'd like to run some intervals this week get that started, but I want to make sure I don't do more harm than good.