Cycling miles to running miles. What's the conversion ratio?

January 3, 2007 1:39 PM

I'm training for an ultramarathon in the summer and I'm trying to get my weekly mileage totals up. However, there might be several times a week when I'll be mountain biking circa 80 km/50 miles in a day. My question is: if I was to try and convert these cycling miles into running miles, how many running miles would 50 cycling miles be worth? What would the conversion ratio be like?

Assuming both cycling and running are done at moderate intensity, if that matters.

posted by dropkick to health & fitness (20 comments total)

I just finished the ride today, and it kicked the snot outta me. I figure it's worth 10 miles running (5:1) but I'd like other perspectives. Maybe I should go by caloric expenditure? METS?
posted by dropkick at 1:46 PM on January 3, 2007

Really there is no way to equate the two. 6 hours of cycling is way easier than 6 hours of running, if your skill/experience in the two is comparable.

I used to race bikes, and I recently completed my first marathon, and my experience is that there's very little in common between the two, other than you'll get a good set of lungs either way. In summer, I still get out on my bike - about 150 or 200 miles a week; I also try to run 25-30 miles. That's a lot of exercise no matter how you add it up. Even so, the running does not make me a better cyclist nor vice versa, except for the good cardiovascular condition each activity helps create and maintain.

If you are running an ultra, no amount of cycling will help you if you aren't putting in your (running) miles. Cross-training is great, I'm all for it, but you can't equate any number of miles pedaled to miles run.
posted by Mister_A at 2:07 PM on January 3, 2007

I'm a marathoner/road cyclist myself and have always wondered about this. I've heard 3 miles cycling is roughly equivalent to 1 mile of running, but I think the answer is varied and lies in the kind of cycling you're doing. The easiest way to compute this would be in terms of caloric energy expended. I've used this site to put some rough numbers into this equation during my training for a few years. Given my weight, an hour of cycling at 16 - 18MPH burns 982 calories, while an hour of running at 8:30 burns 932.

You're talking about mountain biking, which might be harder to quantify since your exertion levels vary more than if you're out mashing the pedals on the road. Still, give that site a try and good luck with your ultra!
posted by hollisimo at 2:09 PM on January 3, 2007

But yeah, what Mister_A said about specificity in training is probably more relevant. If you want to run an ultra, run a lot.
posted by hollisimo at 2:11 PM on January 3, 2007

Thanks for the input thus far, and I agree with everything that has been said.

As for my previous statement, I should've said "I figure it's worth at least 10 miles running" and even 3:1 sounds fair since I was wearing a backpack with about 15 lbs of crap.
posted by dropkick at 2:22 PM on January 3, 2007

I plan on piling on the running miles btw, but the cycling time is necessary and the energy expenditure needs to be factored in somehow.
posted by dropkick at 2:39 PM on January 3, 2007

It should be pretty easy to calculate the number of calories burned per hour, which you can compare to the number you'd burn running. Most cycling calorie calculator widgets go by speed on road, so compare your perceived effort (offroad) to a speed that produces a similar level of exertion to get a rough idea of how many calories you're burning. 50 mi. trail ride = lotsa calories in any case.
posted by Mister_A at 2:44 PM on January 3, 2007

You don't define "worth." If you mean calories or aerobic fitness, there may be an equivalent, but no amount of biking will prepare your legs for an ultramarathon. You have to run ultra-long distances to get ready for that.
posted by Dasein at 5:13 PM on January 3, 2007

Which one are you doing, DropKick?

(I ask because I'm doing my first 50k in a few weeks and will be diving into longer distances shortly thereafter.)

Of course, the best place to ask this is the ultrarunning mailing list.

What's the biking terrain like? Are we talking pretty serious technical hills and whatnot?

In the end, I'm not sure how much it matters what the actual conversion is. You're getting out, getting a really good workout, where you're using different muscles and developing different skills then when you're plugging out the miles on foot.

As far as I can tell, there's no reason not to mix it up. I swam several days a week while it was too hot to run over the summer and completed a reasonably quick marathon without too much trouble.

In terms of training, I just compared the activities time-wise, and that seemed to work out just fine.
posted by ph00dz at 5:57 PM on January 3, 2007

Why is the cycling necessary? Do you need to cover a lot of ground in a certain time (eg using a commute to supplement training)? Is it to reduce the impact on your body to allow for faster recovery so that you can spend more time training (much like mountain bikers use road training)?

I agree with what everyone else has said about specificity. You can't train to run longer just by running heavier, you can train to run by riding other than the aforementioned cardio conditioning. And even then, in my experience the breathing rhythms and type of exertion are so different that there's little carry-over.

It might be of interest to you, but there's some research to support the idea that short bouts of very intense exercise can have a positive effect on endurance (I stumbled onto this via CrossFit. I'll try to remember to find the specific article, but I'm fairly sure it was mentioned at powerrunning.com.
posted by eek at 6:32 PM on January 3, 2007

Ok... I'm not likely to get around to it later, but try these as a starting point.

Googling for "The Surprising Effect of Sprinting on Endurance"
Six sessions of sprint interval training increases muscle oxidative potential and cycle endurance capacity in humans
posted by eek at 6:36 PM on January 3, 2007

If we just think about level ground in calm weather when cycling, wind resistance is by far the dominant use of energy (could be 90%, I guess). Since wind resistance goes up by the square of your speed, the exercise you do is profoundly dependent on the average speed you sustain - 40km/h is almost twice as hard to sustain as 30km/h, even though it is only 25% more distance. So, there is no way to use distance as a metric for the amount of work you do when you are out on a ride.

I don't run, but at a guess, I'd say wind resistance accounts for less than half of energy use while running. So ya, different..
posted by Chuckles at 7:26 PM on January 3, 2007

(could be 90%, I guess)

Could be 90% at 35km/h, I guess.. As speed goes down, the fraction of energy used to counter other losses goes up..

So, there is no way to use distance as a metric for the amount of work you do when you are out on a ride.

No way to use distance or time as a metric..
posted by Chuckles at 7:29 PM on January 3, 2007

Which one are you doing, DropKick?

(I ask because I'm doing my first 50k in a few weeks and will be diving into longer distances shortly thereafter.)

It's a fat ass run I'm organizing for a Saturday sometime in July in Ontario Canada. I'll publish more information on it in a few weeks time, when I have some details ironed out. I will email it to you if you wish.

What's the biking terrain like? Are we talking pretty serious technical hills and whatnot?

No, not technical (although there are some great trails in my area). It's mostly highway, some hills and a bit of off-roading. I'm going to college in a neighbouring city and plan to ride there a few times a week, weather permitting.

In the end, I'm not sure how much it matters what the actual conversion is. You're getting out, getting a really good workout, where you're using different muscles and developing different skills then when you're plugging out the miles on foot.

After today, especially after riding hard for 40 km against a steady wind, I feel like I ran 12 or so miles.

As far as I can tell, there's no reason not to mix it up. I swam several days a week while it was too hot to run over the summer and completed a reasonably quick marathon without too much trouble.

I think the cycling will help stave off wear and tear and give me a good cardiovascular workout, as many have mentioned. And riding is just plain practical for me.

In terms of training, I just compared the activities time-wise, and that seemed to work out just fine.

That's encouraging to hear. Thank you.
posted by dropkick at 7:38 PM on January 3, 2007

All the answers are well articulated and much appreciated. I'm going a little crazy with the "mark as best answer" feature, so any that weren't marked as such, please know I highly regard your comments also. Thanks again.
posted by dropkick at 7:47 PM on January 3, 2007

I hope you're not asking because you intend to substitute some cycling for some running in your training regimen. Doing so would be ill-advised, because it's apples and oranges.

Others have mentioned already that cycling and running use opposite muscle groups. The much bigger problem is that running is a high-impact sport whereas cycling is not. There is no way to build and maintain tolerance to the pounding that running subjects you to, except by running. And the more fatigued you are, the less your musculature protects your bones and connective tissues from injury. So run you must, and you must run lots.
posted by randomstriker at 8:14 PM on January 3, 2007

Sure. Send some info my way... email is in the profile. Always curious what folks are up to and if you're ever down in the southwest, I can point you in the right direction, trail-wise.

Anyway, I'm of the opposite school, randomstriker. I think it's important to get variety. Sure, there's no replacement for that brutal once a week long run, but I guess I think of the rest of week as pretty much interchangeable with any kind of serious physical exercise.

I guess it all depends on your goals.

If you're in good general physical shape, it's pretty amazing how much punishment your body can take when you put yourself in the right mindset, find the right rhythm, and consume enough calories to keep moving.
posted by ph00dz at 9:30 PM on January 3, 2007

Variety and cross training definitely good things to be sure, but they don't address the key point that randomstriker raised about the pounding running gives you.

So run you must, and you must run lots.

Keeping in mind that you don't want to pound yourself into dust, perhaps you could sub in sessions on different surfaces (track, grass, sand) to keep yourself fresher.

it's pretty amazing how much punishment your body can take when you put yourself in the right mindset, find the right rhythm, and consume enough calories to keep moving

Yes, but just as important in training is avoiding the dreaded demons of overtraining. The best advice I read last year was that 'most over training is actually under recovery'. Recovery is food and sleep. Food is the molecular support for every type of tissue and process in your body, sleep is regeneration time, so eat and sleep enough, and eat and sleep well.

Good luck!
posted by eek at 9:51 PM on January 3, 2007

More great comments!

I do resistance training too, especially the major compound movements and especially, especially squats, and I know this has attributed positively to my running. Is squats and running apples and oranges? Absolutely, but they're also interrelated.

I think ph00dz really nailed it, and the experts in the running magazines confirm it: you can't replace the long run. It has to be done. I also agree with ph00dz comments about finding the right rhythm and consuming enough calories. Spoken like a true runner!
posted by dropkick at 6:37 AM on January 4, 2007

Since wind resistance goes up by the square of your speed, the exercise you do is profoundly dependent on the average speed you sustain - 40km/h is almost twice as hard to sustain as 30km/h, even though it is only 25% more distance. So, there is no way to use distance as a metric for the amount of work you do when you are out on a ride.

Might be a best answer, but it is wrong :)

Energy = Force x Distance

so,

Power = Drag x Velocity

Since Drag is proportional to v², the rate of energy use goes up by the cube of velocity, not the square.
I also made the markup vs. margin error.. 33% more than 30km/h is 40km/h, even though 25% less than 40km/h is 30km/h.

A better estimate is that 38km/h is twice as hard to sustain as 30km/h, and only 27% further.
posted by Chuckles at 2:34 PM on January 16, 2007