The running science blogosphere has been popping over the past few weeks with articles touching on various aspects of the role of stride rate in running, particularly how it relates to both running speed and injury prevention. Here’s a quick summary of some of the relevant posts:
1. Back on February 5, I wrote a post on gait retraining in which I described physical therapist Blaise Dubois’ approach to treating broken runners in part by getting them to up their cadence to between 170-190 strides per minute. He has had good clinical experience using this approach, and the scientific literature base on the benefits of gait retraining for the treatment of running injuries is growing.
2. Jay Dicharry from the UVA Speed Lab weighed in and suggested that adopting a running form that incorporates a foot contact closer to the center of mass can be an effective way to reduce vertical loading rate (the speed at which force is applied to the foot upon ground contact), even if footstrike is still on the heel. Increased loading rate has been linked to some types of running injuries, thus reducing it could be useful from an injury prevention standpoint. In his post, Jay also points out that “barefoot running, minimalist running, and increasing cadence (faster cadence means you don’t have time for your foot to reach out far in front of the body) are all effective tools to accomplish the end goal of decreasing loading rate.”
3. On his Runner’s World Peak Performance Blog, Amby Burfoot praised the simplicity of the stride adjustment approach, and discussed the ubiquitous 180 stride/min number that we see commonly thrown around as a target cadence these days. He joked that he “wouldn’t be surprised if runners soon know their stride rate as well as they know their height, weight, cholesterol and blood pressure.” He also measured cadence from a few elites on YouTube, and suggested we be wary of trying to match the cadence of Olympians (good advice!).
4. Next, Steve Magness over at the Science of Running contributed his thoughts, emphasizing in particular that a 180 cadence is not a magic number that all runners should strive for. He views stride rate as a more individualized variable – each person may be a bit different in their “ideal” stride rate. Steve also focuses on the relationship between stride rate, stride length, and speed, pointing out that runners can and do manipulate either rate or length to increase their running speed (here’s a great, older post by Steve on this topic). He concludes by pointing out that stride rate is an outcome of your biomechanics, and that it should change as a result of your form, and that striving solely to adjust rate directly may not be the right approach. He worries that we focus too much on stride rate because it’s easy to measure.
5. Finally, Alex Hutchinson at Sweat Science wrote two posts on the stride rate-stride length topic (here and here), and he also points to data that speed increases can come about by manipulating either stride rate or stride length. I sent Alex a paper (Weyand et al., 2000) I had just read on the topic, and he posted a graph (see above right) from that paper showing that initial increases in speed seem to occur more-so by manipulating stride length, whereas achieving top speed seems to involve increases in stride rate once stride length levels out. Alex also posted an informative interview with Max Donelan of Simon Fraser University, who stated that stride rate is often correlated with an increase in stride length based on his observations while conducting research to develop a device that uses sound cues to manipulate running stride rate. This seems somewhat counterintuitive given that the goal of increasing cadence is typically stated as being to shorten stride – I’ll explain why this isn’t exactly a correct way to think about this in more detail below.
In an attempt to summarize all of this great discussion, I’d like to add some of my own additional comments and observations. Here goes:
1. Recent discussions of cadence/stride rate and the “magic” 180 number have mainly focused on the role of increasing cadence as a means to reduce injury risk. Why is this important? Steve Magness really hit the nail on the head in his post:
“Why is everyone in a rage over increasing stride rate? Because as I’ve pointed out before, most recreational runners simply overstride, which artificially creates a very low stride rate. Why? Because the foot lands so far out in front of the Center of Mass that it takes a while for your body to be over it and ready to push off. So, when some running form coach says to increase stride rate to X, what ends up happening is the runner is trying so hard to increase stride rate, he chops his stride a bunch by putting his foot down earlier and landing closer to his center of mass, thus decreasing the overstriding. Nothing particularly wrong with that.
Where we go wrong is in the logic that the stride rate increase is the key. No, it’s not. It’s the elimination of the overstriding. Using the cue to increase stride rate is a way for coaches/runners to reduce the heel striking overstride.”
The point that Steve is trying to make is that overstriding is the evil we are trying to correct by manipulating cadence. In other words, increasing cadence is not the goal in and of itself, rather, it is a means to achieve the goal of eliminating the overstride. What is overstriding? Defined simply, it is running in such a way that you reach forward with the lower leg and land heavily on the heel (usually) with an extended knee. The four images below all show overstriding in runners recorded at the 10K mark of the 2009 Manchester City Marathon – all four depict the exact moment of first contact between the foot and the ground.
What we ultimately want is to avoid reaching out with the lower leg, and by doing so thus prevent landing on the heel with an extended knee. Ryan Hall from the 17.5 mile mark of the 2010 Boston Marathon provides a good example of a non-overstriding gait with a midfoot landing, a bent knee at contact, and a more-or-less vertical lower leg:
Current thinking is that increasing cadence helps to reduce overstriding because it forces you to put the foot down faster and closer to the center of gravity. Amby also discusses this in his post, saying “Dicharry believes load-rate is important, but not necessarily footstrike. He simply wants runners to be wary of overstriding, i.e., running with a low stride rate that results in placing the foot ahead of the center of mass.” In other words, reaching with the leg is bad, and increasing cadence can help us avoid doing that. Let me repeat – overstriding is what we are trying to prevent by manipulating cadence. If you don’t overstride, manipulating cadence might not be wise or necessary.
Regarding the observation mentioned above from Max Donelan that increased stride rate is usually correlated with increased stride length, my guess is that increased length might be due to greater hip extension on the back side rather than by reaching out front when we up cadence. I may need to get my camera fired up in order to experiment with this hypothesis – more reason for my neighbors to think I’m nuts!
2. Regarding speed, it seems pretty clear that stride length and stride rate interact to increase running speed. Which of the two is relied on as the primary mechanism may vary somewhat from person to person, and with different speed ranges.
As so often happens with me, when I start mulling something like this, I feel the need to experiment on myself. I have a Wahoo Footpod that syncs with my Garmin Forerunner 305 and outputs stride rate in real-time, so I’ve been monitoring my cadence on my runs of late to see what I do out on the road. I’ve noticed that my cadence fluctuates right around 186 strides/min over a fairly wide range of speeds, from about 7:00/mile up to about 9:00/mile. However, when I push faster than a 7:00 pace, my stride rate ticks up, and I’ve seen it go as high as 200 when I really start to push the pace. What this tells me is that for most of my easy pace running, I regulate speed by changing stride length, but when I want to go fast, I increase my turnover and jack up the cadence. I was never aware of this until I actually measured it. For visual proof, below is a graph from a recent run showing cadence over the course of a 7 mile run – can you spot the two times I pushed the pace below 7:00 min/mile?
Here’s another graph showing my cadence (green) along with pace (blue) and elevation (brown) from a 15 mile training run (avg. pace = 7:58 min/mile) I did yesterday (click on the image to view a larger, clearer version):
What you’ll notice in the above graph is that my cadence stayed remarkably steady throughout the entire run, even though speed and elevation fluctuated a bit – average cadence was right around 186 strides/min. There was a slight uptick on the big downhill between miles 11-12, and also at the end of the run, which can be attributed to the fact that I was running on ice and had shortened my stride a bit to avoid slipping.
Based on this it seems that at least for me, initial speed changes are accomplished by varying stride length, whereas really picking up the pace requires an increase in cadence. I’m wondering if I reach a point where I can’t increase stride length much further, and any speed increase beyond that can only be accomplished by increasing cadence? Interesting to idea to ponder…
I also don’t know if my cadence has changed at all since moving into more minimalist shoes and working on my form over the past 9 months – I never measured my cadence prior to sometime last summer, and even then it was just by counting steps once or twice on a few runs. It seems right now that my body has found a comfort zone, and I look forward to experimenting a bit more with different speeds and shoes to see if things change.
3. How do shoes tie in with all of this? My view regarding minimalist shoes is that they can help you accomplish better form because the reduced heel helps prevent you from overstriding (particularly if you run at least periodically in something very minimal like the Vibram Fivefingers or Merrell Trail Glove). You can probably reduce overstriding in any shoe given enough effort, but it will be harder in a shoe with a typical 2 to 1 heel to forefoot thickness ratio (i.e., 12+ mm drop shoes), and part of me wonders if running with barefoot-style mechanics in a heavily lifted shoe might cause some problems – we just don’t know at this point.
I do know that a heel lift as small as 4-5mm is enough to pretty much negate any calf soreness I might get from running hard in a barefoot-style shoe like a Vibram, and for me this seems to be the sweet spot when it comes to speedwork, long distance training, or a marathon. I do a lot of training in zero drop shoes as well, and my opinion is that you can’t beat barefoot or something like the Vibrams/Merrells when it comes to working on getting a feel for your stride. When working on my stride last summer, I never paid attention to my cadence. Rather, I used Vibram runs and the cue provided by Steve Magness to “put my foot down behind me” – these worked well for me, and it is clear that there is more than one way to accomplish arriving at a form with a landing closer to the center of mass.
4. Finally, if you do feel that you are an overstrider and choose to manipulate cadence, I am a bit wary that the 180 number might get over-applied. Personally, I like the idea of finding your current cadence and upping it by 5-10%. There is evidence in the scientific literature to suggest that this can be of benefit, and it forces you to progress from your own baseline rather than striving to achieve a number that might not be appropriate for you.
5. Lastly, and it bears mentioning once again, any change you make should be gradual, and should be done with good reason. If your stride ain’t broke, don’t try to fix it. You may wind up doing more harm than good.
This post is part of the Minimalist Running Blog Carnival – many thanks to Jason Fitzgerald at Strength Running for organizing. To view other posts in the round-up, visit http://www.strengthrunning.com/2011/02/minimalist-blog-carnival/