Is rededication to exercise one of your New Year's resolutions? Are you thinking about what to do for cardio and calorie burning? If so, the following might interest you.
In another blog, a discussion of running versus walking came up. One commenter said that walking and running burn the same amount of calories per hour. I offered that they don't burn the same amount per unit of time, they burn the same amount of calories per unit of distance. Basic physics. Moving a specified mass over a specified distance requires the same amount of energy regardless of speed. And since runners generally cover more ground per unit of time than walkers, they usually burn more calories per unit of time.
The commenter responded that my observation is "predicated on the assumption" that runners move faster than walkers and the commenter insisted that they generally don't.
I'm sure some walkers walk faster than some runners; I was speaking generally. I think they move faster on average, but I never studied the question.
The commenter also cited Dean Ornish, (WebMD, no link provided):
"...walking a mile will burn more calories than running a mile -- although it takes longer to do so. When you run a mile, you're burning mostly sugar, or carbohydrates, which is how your body gives you fast energy in bursts. When you walk a mile, it gives your metabolism time to switch from burning carbohydrates to burning fat."
That Ornish says "it takes longer to do so" would seem to confirm what I proposed about time running versus walking, though the rest of his statement argues against the simple physics position on distance covered and calories burned. This is the opposite of a possibility I've considered. I've thought that if there is any difference at all, running might, on average, burn a few extra calories if the step is higher. Certainly that wouldn't be true for all joggers and all walkers. Some fast walkers might even burn a little more than some very slow joggers. In any case, I've assumed that any differences would be so small as to be negligible.
A quick search turned up a study in which the researchers actually measured and compared calories burned by walking versus running. It turns out, according to their findings, that running doesn't burn a little more per unit of distance; it burns a lot more per unit of distance--30% more! And that holds true for both genders. Apparently the body is doing considerably more work to cover each unit of distance when running versus walking. This came as a surprise to me, though I imagine it's not a surprise to some serious runners.
The science of energy expenditure aside, walking still has it's own great advantages. It's less hard on the joints, and, IMO, it's a more pleasant way to enjoy the outdoors. And if you've got an exercise partner, it's somewhat easier to hold a conversation. But if joint problems aren't an issue for you, and you have no particular preference for running versus walking, it looks like running is the far better choice for calorie burning.
Since I have some joint concerns, I've opted for the incline treadmill, set at a speed right at the border between walking and running. But I also use a steep incline to increase the work done per unit of distance covered. I think that exploits the advantages of both running and walking, except of course that it's indoors rather than outdoors. Fortunately, I can watch that little TV on the treadmill and catch all those cable shows I miss without cable at home. If not for the treadmill, I wouldn't know anything about the antique pickers, the pawn brokers, those guys who love their guns and the guy who does filthy jobs.