Changing your Stride Frequency
“Quick feet, quick feet!” My high school coach used to shout as we launched into the last lap of a track race. More often than not, this was not helpful, as I usually ended up drifting into a long-legged loping gait as I strained my way towards the finish line.
However, my coach was onto something: if you want to run faster, you’ve got to do one of two things: increase your stride length or increase your stride frequency.
The latter of these two options has attracted attention recently, not just because it can increase your speed, but because it may decrease your risk of injury.
The logic is as follows: Increasing your stride frequency (the number of steps you take in a minute of running) decreases the amount of impact you have to absorb with each footstrike, and thus the overall strain on your body is lessened.
But, as with many things in running, we can’t just trust theories—we need evidence. What if injuries are not caused by large impacts, but instead very small trauma that builds up over time? In that case, a higher stride frequency would be worse, since at a higher cadence, it takes more steps to cover a given distance.
The science of stride frequency
First, we have to figure out whether impact has any affect on injury risk. Thanks in large part to the barefoot running craze, there has been a flurry of research on this topic in recent years. Two such studies, both conducted by Irene Davis (no relation) and her colleagues at the University of Delaware, looked at whether impact forces were related to two common running injuries: plantar fasciitis and tibial stress fractures.
Impact forces and occurrence of plantar fasciitis and stress fractures
Both studies (the first on plantar fascia injuries and the second on stress fractures) recruited female runners with a history of plantar fasciitis or tibial stress fracture. The runners were evaluated using force plates and 3D cameras to examine their biomechanics. The results from the previously-injured runners were compared against age- and mileage-matched women who had never suffered a tibial stress fracture or plantar fasciitis.
While the results showed no difference in joint motion (save for ankle dorsiflexion in the plantar fasciitis group) and total impact force, Davis and her coworkers did find a significant difference in impact loading rate, which is essentially how hard you hit the ground when you run.
It’s important to note that these studies were retrospective: they only looked at runners (indeed, female runners exclusively) who already got injured and had recovered. Perhaps their high impact loading rate was caused by their injury. Furthermore, a prospective study by Canadian researcher Benno Nigg found that the total number of injuries decreased slightly for runners with high impact loading rates. Unfortunately, this study was done mostly as a doctoral thesis, and the details are not published.
So, the issue is far from resolved. Irene Davis’ lab is currently working on prospective studies, hoping to show the same effect—that high impact loading rates increase injury risk for specific injuries. But let’s propose that Irene Davis is correct, at least for tibial stress fractures and plantar fasciitis: suppose loading rate is correlated with injury risk. Is there anything we can do about it?
Loading rate and injury risk
A 2011 study at the University of Wisconsin attempted to answer the question about the correlation between loading rate and injury risk.
Some 45 healthy recreational runners were recruited to run on a treadmill at their normal easy run pace (between eight and nine minutes per mile for most). Again, using 3D cameras and force plates, the researchers analyzed the stride characteristics of the runners. This time, however, after a control run, the runners were asked to increase or decrease their stride frequencies by 5 and 10% for four additional trials. Using computer modeling, the researchers were able to piece together exactly how the body distributed the impact force amongst the ankles, knees, and hips. Though they didn’t measure the loading rate directly, they monitored the impact transient—the spike in forces at footstrike associated with a sharp loading rate.
As predicted, when the runners increased their stride rates, the energy absorbed by the hip and knee joints decreased significantly (interestingly, the energy absorbed by the ankle did not change significantly). And sharp impact transients decreased at higher stride frequencies. The converse of this is also true: energy absorbed and impact transients increased when the subjects were asked to decrease their stride rate. The magnitude of the effects increased when the subjects moved from ±5% to ±10%. So it appears that increasing your stride frequency by five or ten percent is a good way to decrease the impact loading on your joints and possibly prevent injury.
What does this mean for your running?
This still leaves us with a very big “if”—if impact loading rates and joint loading are connected with injury, then increasing stride frequency should help prevent injuries from occurring, right?
Substantial evident points towards at least some injuries being caused by steep impact loading rates and large forces acting on the joints, but we won’t have a definitive answer until there are more prospective studies: ones which examine a large group of healthy runners and see who gets hurt and who stays healthy.
Until then, I think increasing your stride frequency is not a bad idea, particularly if you’ve suffered from stress fractures or plantar fasciitis. There’s plenty of anecdotal evidence too: elite runners tend to have a fairly high stride frequency, 180 steps per minute or more, even at slow paces, while recreational runners tend to have quite a low stride frequency, sometimes as low as 150 or 160 steps per minute. For more information on what number you should target, read our article on optimal stride rate for runners.
How to improve your cadence
A good way to check your own stride frequency is to count the number of times your right leg hits the ground in 30 seconds of running. Then quadruple the number to get your overall cadence.
Fortunately, it’s easy to compute a 10% change—if you count 41 right-foot strikes in 30 seconds, increasing 10% (4.1 strikes per 30sec) would bring you up to 45. And 5% would be half that, bringing you up to 43 strides per 30sec.
Runners have adopted a variety of cues to increase their stride frequency. One method is to think about “quick feet”, like my high school coach encouraged me to do. Personally, I’ve found this to be the best method as I periodically check the cadence of my runs.
Another common method is to listen to music with a specific beat (there are even websites with premade mixes at 160, 170, and 180 beats per minute!). You could also use a metronome app for your phone, which will set a steady rhythm for you to concentrate on.
Finally, you can simply try to match the cadence of another runner with a higher stride frequency.
While the impact and injuries question is still unresolved, hopefully trying to switch to a quicker cadence will keep you light on your feet and injury-free.