run cadence (or...how do I use this new footpod?)
Got a Garmin footpod for Christmas. First run with it today. I've not paid much attention to run cadence in the past (occasionally would count, but rarely). Hoping some of you running gurus can help me (if I'm not doing it right)?
Ran one hour today, with 3 x1 mi at Z4 (which for me is 7:20/mi currently). My cadence in the Z1/2 sections during w/u and between intervals was 85-90 (slower I was going, the closer to 85 and vice versa). During my threshold interval miles, avg cadence was 93...all three times.
From what I've read in the past (can't find anything in the wiki tonight), target should be ~90? Is it ok for cadence to be a bit slower at the Z1/Z2 paces? Anything I need to do differently? I know speed boils down to cadence + stride length, and I recall Al T. mentioning that both need to increase with faster paces, right?
I feel good while running (form wise), even when running "fast". I remember posting a question at this same time last year when I felt out of control during threshold intervals....and lo and behold....I'm a solid 1:00/mi faster than last year at this same time (training peaks biopsy proven!).
Thanks.
Comments
Jeff - a few thoughts on cadence. First, one of our spreadsheet jocks (was it Prof Jenks?) took a look at his cadence relative to speed and found a direct, almost linear correlation between his speed and his cadence, just as you are finding. Another WSM (was it Dave Tallo), tells about his efforts to increase his cadence over the years; he tries to hit 90 no matter what speed he's going.
My particular take is related to racing. I theorized that, similar to cycling, running with more steps over the same distance (that is, with quicker cadence/shorter strides) at the same speed might result in lower overall energy use. So I bought a foot pod, and, like you, when I first started using it, I saw that I was going 86-88 when going @ LRP, and my cadence would increase with speed from there. For a few months, especially when doing bricks, I would put my sole focus on the first mile or two at getting to a 90 cadence. Initially, looking at my race rehearsals, my cadence would be in the 86/7 range. I now can do an IM marathon (at LRP or slower) with a cadence of 90, and do my TP intervals @ 97, and my VO2 intervals @ 99-100.
My simplistic thought process was: if I could keep the same stride length, and take 8 more steps a minute, I'd end up going 4.5% faster (8/172). It probably doesn't work like that; more likely, I'm take shorter strides, but using less energy with each one.
I don't think there is automatically any ideal cadence; the taller/large one is, the lower the cadence might end up being. But I also think that 90 is a well-tested rpm to shoot for; e.g., most world class marathoners run in the 90s. And probably most of the better IM marathoners on our team (and I suspect as a general rule in triathlon) are trying or succeeding at hitting 90 RPM on race day.
All the data I've seen suggest you're in a healthy range. 90+ when you're running fast and ~85 when running slowly. This is very normal. There are people out there who suggest that humans can/do run the same cadence no matter what speed, but any such human is a rarity...normal people have higher cadence when running faster than when they are running slower. My data had a particular fraction for me, but I've read plenty of times about treadmill tests and so on that suggest this is the general phenomenon.
Now, when you are running an IM leg, you won't be running that fast. I have no doubt about hitting close to 90 in an open marathon...I just looked at my last 2 and hit 88 average for each of them. I'd like to be a little higher, but I'm ok with it. I am going to work a bit on increasing my cadence at the slower speeds for my 2014 IM, but honestly, I think it will come more as a general cadence lift than because I can specifically increase them at my EP and change the slope of my pace/cadence curve a lot.
I just happened to be reading today the chapter titled "Run" in Jim Gourley's recent book on the scientific underpinings of triathlon training and racing, Faster. I found this quote in his review of studies about running efficiency and cadence: "a slow, shuffling runs consumes more energy per step than the quicker, springier turnover of fresh legs." [Emphasis added]
This is basically the theory I was going on in my attempt to get my IM marathon cadence to 90, despite running at a pace that I "normally" would have a cadence of about 86-7 for. The biomechanics researchers postulated that a quicker cadence results in less time of foot contact to the ground. This has several benefits (again, quoting from the book):
Basically, a death spiral.
Gourley claims that biomechanical studies demonstrate that a cadence of 180-190 steps per minute is the ideal to best balance horizontal and vertical displacement - IOW, bouncing as little as possible while leaping forward as much as possible. His book has footnotes, but I can't correlate the studies he quotes with any particular number from a biomechanical perspective, only from observations of successful runners, who all seem to adopt this cadence.
To reiterate: an IM marathon disrupts our normal cadence. Our legs are already tired, so we are inclined to run at an RPM which will make us more tired more quickly. Training ourselves to take shorter, quicker steps at slower speeds when tired will probably result in less progressive fatigue during the 26.2 miles we run on race day. Going @ 90 rpm, even though you may only be running at LRP +0-90 seconds (depending on temperature, point in the race, etc) is preferable to an rpm of 85, which might be the "natural" cadence you would adopt at that pace. A footpod used during bricks and during the race itself may be a useful tool to learn, adopt, and maintain that more desirable cadence.
JW, Al, and Prof Jenks....great stuff! Exactly what I needed.
I definitely can feel the urge to "shuffle" as I get fatigued (although I'm not doing anything long enough right now to create real fatigue). Will focus on keeping the cadence up as I get tired and during bricks/etc. I have noted that when I notice the cadence approaching 85, that if I just pick up the cadence a bit, the pace comes up a bit, without much if any added RPE.
Thanks for the insight Al, John & Will.