Factors that affect calories burned

-amount of stress that you're under

-amount of adrenaline thats pumping through your body

You could walk 5k and burn the same calories. It just takes longer.

That being said, I believe after higher intensity exercise you continue to burn calories for a while longer.

It is based on energy used, which is in turn based on work performed by muscles. To a first approximation, work done by muscles is proportional to mass moved over a given distance, hence the presumption of constant calories per mile and calories proportional to your body weight.

If you switch back and forth between anerobic and aerobic running (such as interval repeats), each of these pathways has a slightly different efficiency at converting stored energy into work done by muscles. In addition, if your stride and biomechanics become less efficient as you get tired, you might burn more calories per mile. On the opposite hand, if when you run fast you are leaping higher into the air with each step, you are doing more work by lifting your body weight a larger distance against gravity with each step, say compared to a shuffle where your head barely rises up with each step. However, there is also the factor of how much energy is wasted by braking forces if you overstride, and how much energy is wasted each time you accelerate your thighs forwards (although that almost cancels out since it is based on the ground surface covered with each step).

The other aspect is there is the resting metabolic rate to compare to, since if you were not running your heart would still be beating, burning about 45 calories per hour. So if you want to know how much more you have burned relative to being sedentary, you should subtract the sedentary calorie burn.

Like it was said before...the rate at which you run has no impact on the number of calories you burn. Running or walking 5K will yield the same number of total calories burned...it'll just be done quicker by the runner.

One thing you can control that will impact the number of calories you burn/mile is your incline. Obviously this is easy to see on a treadmill...

It'd be nice if you burned more calories running in the heat than the cold, but I don't think it affects it much at all. I hope I'm wrong on that.

my run in heat and humidity yesterday was misreable, it'd be nice to get a bonus out of it other than dehydration and stomach cramps.

[quote]whaler wrote:

Like it was said before...the rate at which you run has no impact on the number of calories you burn. Running or walking 5K will yield the same number of total calories burned...it'll just be done quicker by the runner.

quote]

This is not true.

It absolutely is true...it's physics 101...work done. Do you have anything to prove me wrong other than your 4 word response? I think not.

Good point. I forgot that both running and walking are 100% efficient.

It's not true, the faster you run the more wind resistance you have to overcome, and the more heat you generate. When you walk a mile in 15 minutes you don't generate a lot of heat, but running a 4 minute mile generates a huge amount of heat.

There is more to this than the amount of oxygen uptake and the anaerobically generated energy supplies.

Human bodies are NOT point masses--the dynamic differences between walking and running include vertical "jumping" and disproportionate heat generation. Running burns more calories, i.e. it is less efficient.

Amby Burfoot article exploring this concept:

http://www.runnersworld.com/article/0,7120,s6-242-304-311-8402-0,00.html

Although Burfoot references different formulas in his article, here are the more clinically accurate ACSM Metabolic Calculations presented in most exercise physiology texts:

Walking

VO2 = (0.1• S) + (1.8 • S • G) + 3.5

Running

VO2 = (0.2• S) + (0.9 • S • G) + 3.5

(S= speed in m/s; G= % grade; 1 L O2/min = 5 kcal/min; Cal = kcal)

Remember that the total number of calories expended is the net number burned during exercise plus the basal metabolic rate. Whether you run or walk for an hour, you would have burned a certain amount just sitting there.

Post Script:

Whenever this topic comes up, I always think of the ROM exercise machine advertisements in airline magazines.

http://www.fastexercise.com/

4 minutes a day. Yours for only $14,615.

"No! No, no, not 4! I said 5. Nobody's comin' up with 5. Who works out in 4 minutes? You won't even get your heart goin, not even a mouse on a wheel."