Friday, February 03, 2006

Split run and cadence

I did 4 miles on the W&OD rail-trail this morning, but looking at the forecast, I was afraid that it would be pouring rain all day tomorrow and I wouldn't want to run in that. So I went out just before sunset and did another 3 miles on the track to complete my personally-assigned weekly minimum mileage this week. Both times I was averaging a comfortable 12 min/mile pace (or .0833 miles/min).

I did something new - counted my right footfalls for one minute to determine my comfortable running cadence. I repeated it four times - so counts of 86, 84, 83, and 83 average out to a stride frequency of 84 strides per minute.

Now since velocity (.0833 miles/min) equals stride length (in ? miles/stride) times stride frequency (84 strides/min) , then stride length equals velocity divided by stride frequency.

Doing the math, and converting to feet, gives me a calculated average stride length of 5.23 feet per stride when I'm running comfortably at that velocity. Cool!

Of course, any time I increase speed, either stride length or stride frequency, or both, must increase, by definition, so these will vary depending on how fast I'm running.

Additionally, this tells me that my lowest optimal cycling cadence is somewhere about 84 cycles/minute. Or slightly higher, since your leg is somewhat shorter when it's bent when cycling, making a shorter pendulum with a higher natural frequency.

Or maybe not. I may possibly have had a teensy bit too much of the excellent Riesling that we had tonight with the tuna steaks that I grilled for dinner. Yum!

12 comments:

nancytoby said...

Hmmm, just checking to see if Blogspot is buggered up again like it was last night....

nancytoby said...

Nope.

Dawn - Pink Chick said...

Ya know I love math Nancy, but that more than I can think about during a run...lol.

nancytoby said...

It was just counting strides! Not doing math. I can't do math during a run either!!

Dianne W. said...

Doesn't everyone do math when they run? I always have.

Lynne said...

I can barely run and chew gum... Nancy - I think you are taking this exercise thing to a whole new level!!!

blahblahblahblahblah said...

This is what I've read about stride rates. "The Complete Book of Running for Women" suggests that 90 to 95 steps per minute is the optimum stride rate for conserving energy and avoiding injury. "A slow stride rate means you spend more time in the air and thus land harder," says Jack Daniels, Ph.D., sports scientist, about runners who take only 75 to 80 steps per minute. To increase your stride rate you should shorten your stride, not increase your speed, at first. Your stride will naturally lengthen with practice as you become a stronger, faster runner. I've been working on increasing my stride rate, which was slower than yours is. I no longer have to wear clown sneakers to prevent my toes from going numb, and the muscles in my thighs are finally smoothing themselves out for the first time since I started running.

nancytoby said...
This comment has been removed by a blog administrator.
nancytoby said...

Since velocity = stride length * stride frequency, in most cases a low stride frequency means nothing more than ... you're running more slowly than someone using a higher stride frequency!

So sure, if I was running faster, or as fast as the "optimal" elite runners Dr. Daniels probably is referring to, I'd be running with a higher stride frequency.

To compare apples with apples, you have to compare runners (or with yourself) moving at the *exact same* velocity.

PuddyRat said...

Well, Nancy, using your math then, if you decrease the stride length, but increase the frenquency, you have the same velocity, yes? I think the point of most coaches is to get you to increase your frequency (turn over rate) and that then, eventually, your stride length will naturally lengthen, resulting in greater velocity. Does that make sense?

I only mention it because my coach has me counting my foot strikes on some of my runs and we are currently aiming for 22 in 15 seconds. To do this, I must shorten my stride because, like you, I want to stretch it out. However, at this point, doing so makes me slower rather than faster.

I'm also not sure their is a direct correlation between foot strikes and RPM on the bike. I can easily do a ride with a 95 RPM but I think I'd trip if I did that while running. Also, by training my body to cycle faster (cadences of 95-105 rpm), I will train my body to run faster. Well, at least so my coach keeps telling me. She says my cycling will help my running more than my running will help my cycling. Hey, if she gets me through IMC this year, I'll be a believer! :-D

nancytoby said...

Yes, if you both decrease stride length and increase frequency, you stay about the same velocity. Those are interesting aspects, though, Puddy! And you're right, I don't think there's a direct translation to cycling. And when people start talking about "efficiency" usually they're getting onto thin ice, because running faster almost certainly means expending more energy. Unless I lose a lot of weight (fingers crossed!) that is!!

blahblahblahblahblah said...

"I think the point of most coaches is to get you to increase your frequency (turn over rate) and that then, eventually, your stride length will naturally lengthen, resulting in greater velocity. Does that make sense?" ~quoting puddyrat

Thanks, puddyrat. That is what I was trying to say.

At first I felt silly, because I was taking more steps than anyone else traveling at my speed, but now I'm running faster. The improvement seemed so natural. I was taking faster steps and my stride just lengthened because that felt more comfortable. My endurance has increased too and running seems a little easier.

I think the leg muscle reduction is because I'm now making quicker movements and hitting the ground with less impact, lower weights and higher reps. It's kind of like losing a few pounds. It literally is losing inches.