Energy to run a mile = energy to walk a mile? True or False?

Physics Ignoramus wrote:

Thanks for those of you giving serious answers. Maybe my buddy was messing with me or or maybe talking about some sort of ideal conditions with wind resistance, etc.

no, it is just a common misconception. Has anyone provided you with data?

Here:

http://www.ncbi.nlm.nih.gov/pubmed/15570150

Running more energy costly than walking a mile.

Much more recent info, and also includes post-exercise energy expenditure:

http://www.ncbi.nlm.nih.gov/pubmed/22446673

Again, running better than walking as far as burning calories. And these are SLOW runs. Imagine the difference when one includes intense running vs easy walking, and includes post-exercise energy expenditure?? BIG difference. I can walk with barely rising my heart rate above what it is when sitting.

"your" welcome.

I'm no physics expert but it seems the statement is a little misleading to some. Many seem to take that statement as walking is just as good for losing weight or getting in shape. Like others have stated running is less efficient. But that wasted energy is still calories burned. So even if the statement were true you'ld still lose more weight, burn more calories, from running as opposed to walking. Whether the energy is the same or not is really irrelevant when you consider the purpose of the activity.

Ask your physics genius friend, what uses more energy. Driving a car for 10 miles at 90 mph or driving a car for 10 miles at 50 MPH?

Also, how long after the 15 minute walk is your body heated up, how long after a 4 minute mile run is your body heated up? Heat is loss of energy.

I challange the xfit coward number one to a race, any distance, any place, for any amount of money. Xfit makes you chunky-fat.

Limey UK runner wrote:Like others have said walking a mile takes less energy because it is more efficient.

It takes less energy because its slower in absolute terms and its only most efficient at 15-30 minute miles. You could also use even less energy butter up your underside and squirm around like a worm doing 2 hour miles and that would also be very efficient for the speed.

A horse is a good example of the energy efficiency different rates of striding have.

If you have ridden a horse while it is walking you will notice it has a smooth, efficient rhythm. A horse running is not as smooth but still has a rhythm to it. A horse trotting is pounding a lot of energy into the ground, which is being wasted.

The same thing for humans. The walk is most efficient. As you speed up your efficiency drops. But at a certain point (speed), probably having to do with the center of gravity being over the impact point rather than behind it, you become more efficient again, though not as efficient as walking.

Wind resistance and internal temperature build up will also factor into energy waste at higher speeds.

Physics Ignoramus wrote:

My engineer friend was arguing that it takes the same amount of energy to walk say a 15 min. mile as it takes to run a 4 min. mile. He says that this is basic physics.

I don't know physics from a hole in the ground but to me it seems like common sense that it would take more energy to run faster. Is what he says true or is he pulling my leg?

Are you asking if it takes more energy to run a mile than walk a mile or if running uses more energy than walking? They're not the same questions.

Walking takes longer than running so assuming that walking requires less energy, the exerciser would be spending much more TOTAL TIME walking than running. I don't know the math and I assume it varies from individual to individual, but for instance if running uses 20 cal./minute and walking 10 cal./minute, if the individual ran a mile in 4 min. and walked the same in 8 min., the calorie expenditure would be the same.

Real world comparison. When I was injured and couldn't run I walked the same loop I usually ran. It took me twice as long to walk as to run. I did not gain any weight so for me the increased duration of activity canceled out the lower calorie expenditure.

Limey UK runner wrote:

Like others have said walking a mile takes less energy because it is more efficient. Air resistance increases with the square of velocity, running oscillates your centre of mass against gravity to a greater extent, more energy is spent doing work to accelerate the limbs to higher velocities, energy losses during inelastic collisions and losses during elastic return, there are loads of factors. I can't be bothered to do the numbers to find out which factors dominate. Instinct tells me it is acceleration of the centre of mass against gravity.

This is one of those very old myths that will probably never go away.

^This.

It's a matter of input work vs. output work. The output work is the movement of the mass over a displacement, which is independent of path and time. So it takes the same amount of output work to go a mile at any pace as long as you're talking about the same person (same mass).

The input work can vary greatly, and it depends on your body's ability to radiate heat, its ability to return elastic energy on contact with the ground, extent of vertical displacement of the body, wind resistance, not to mention an individual's unique mechanics that may waste different amounts of energy. This is where the difference between walking and running the mile come into play.

Les wrote:

Walking takes longer than running so assuming that walking requires less energy, the exerciser would be spending much more TOTAL TIME walking than running. I don't know the math and I assume it varies from individual to individual, but for instance if running uses 20 cal./minute and walking 10 cal./minute, if the individual ran a mile in 4 min. and walked the same in 8 min., the calorie expenditure would be the same.

Real world comparison. When I was injured and couldn't run I walked the same loop I usually ran. It took me twice as long to walk as to run. I did not gain any weight so for me the increased duration of activity canceled out the lower calorie expenditure.

you're wrong. Did you read my links? Did ANYone read my links?!?! Everyone is pontificating on the hows and whys and maybes concerning potential differences between running and walking, and while some of this is enlightening (most of it not), he wanted a simple answer: True or False. The answer is False, and is backed up my links.

"You're" all welcome.

Physics Ignoramus wrote:Energy to run a mile = energy to walk a mile? True or False?

I would have to say false as far as competition speeds because racewalkers can do 6:50 pace for long distances coupled with their greater walking energy efficiency they should more than be able to win 100 mile track/road races. The american record running pace at 100 mile track is above 7:00 pace. Racewalkers don't have that record or even seemingly compete in it which means the initial assumption of greater energy efficiency must not be right. And if you are less efficient over 100 miles, why would you not be less efficient over 1 mile?

Physics Ignoramus wrote:

My engineer friend was arguing that it takes the same amount of energy to walk say a 15 min. mile as it takes to run a 4 min. mile. He says that this is basic physics.

I don't know physics from a hole in the ground but to me it seems like common sense that it would take more energy to run faster. Is what he says true or is he pulling my leg?

AS others have shown, it is not identical.

However, when I first learned about the topic, I was surprised how close the two actually were to each other per mile. My quick rule of thumb is 100 calories per mile, whether 6:00 pace, 9:00 pace, or walking. It's not exact, but not that far off for an estimate.

the "true physics" is

energy = 0.5 * m * v^3 * s

- for a 70kg guy walking a 15 minute mile, enegy expended =

0.5 * 70 * ( 1609.344 / (15*60) ) * 1609.344 = 322060J

- for a 70kg guy running a 4 minute mile, enegy expended =

0.5 * 70 * ( 1609.344 / (4*60) ) * 1609.344 = 16983604J

don't worry about absolute values ( units ), the relative increase in energy expenditure is

~ x 53

sounds extreme, but here is evidence :

http://www-atm.atm.ox.ac.uk/rowing/physics.html/basics.html#section2

substitute a homunculus for a boat...

speed is it wrote:

butter up your underside and squirm around like a worm doing 2 hour miles

Sounds more Olympic-worthy than race-walking.

ventolin^3 wrote:..

correction : the power output difference is 52+

the absolute energy expenditure factor is (15/4)^2 = 14

Wow, I always knew you were a MORON but this really takes the cake.

You are an ABSOLUTE IMBECILE!

BASIC PHYSICS. Work (energy) = force * distance. So comparing 2 examples of the same distance, the one who is expending more force over that distance requires more energy. In an ideal world, traveling at a constant speed would require no force. with friction, both internal and external, however, it takes more force to maintain a faster speed than a slower one.

All machines (people included) have different levels of efficiency based on utilization rate. For example, if you drive your car at 55 mph on the highway for 100 miles versus 85 mph on the highway for the same distance, you will consume a very different amount of fuel for the same distance. A car could be designed with optimal fuel efficiency at 85 mph, but it may not accelerate from a stop light the way you prefer. The human body has optimal modes of transport. Running at 4:00 mile pace is not an optimal mode and consumes crazy amounts of energy, walking is more optimal and more in line with our design.

The formula does not include TIME in it, just the energy used to cover 1600m. Unsurprisingly running consumes more energy per minute, but time is also a factor since it takes less time to run a mile than walk a mile and the original poster I believe was asking the TOTAL energy required to walk vs run 1600. If that was the question, then time spent doing the different activities has to be factored in. It could take 2-4 times the amount of time to walk 1600m opposed to running so you have to multiply the lower energy walking requirements time time to get a total energy consumed.

Again, there's no doubt running requires more energy but that I believe wasn't the question.

I guess the consensus is that it take more energy to run a mile than to walk it, even if there's not much agreement why that is true. These seem like the clearest explanations, but of course that doesn't mean much coming from me.