Silly question?
 

Are us cyclists like automobiles? What I'm asking is, if I drive my car a distance of 200 miles at 50 miles an hour I use far less gas than if I drove 100 miles an hour even though I got there twice as fast, right?
Is it the same with calories burned during excercise?

Yup. The energy devoted to overcoming air resistance goes up exponentially with your velocity. Going twice as fast burns more than twice as many calories. :)

Let’s take intensity between working at say 65% of MHR and 80% of MHR instead of MPH. AND instead of using miles as a measure let’s use time and calories (fuel). Also this presumes that we keep a steady pace in both arenas which is harder then it sounds.
Say we burn 3 cal/min at 65% (estimate- needed a number) we would burn 180 cal in that hour (3 cal x 60 min) 80% of that comes from fat and 20% comes from glycogen that means 144 calories are burned in fatty acids and 36 cal come from glycogen.
Now let’s take a look at the 80% MHR number where we will burn 6 cal /min or 360 cal in that hour. 50% will come from fatty acids and 50% will come from glycogen or 180 each. Looking at it from the longevity point of view yes you will last longer in the lower endurance intensities where less calories comes from fatty acids that use air to burn but as you use the heat of your engine as you get closer to your max HR you start burning more glycogen and fatty acids and will create the need for a refueling and rest sooner.
Velocity

I can somewhat follow that but please in general terms how does that apply to training or racing? If I really did understand that, my take is:

To train, spend more time at higher heart rates
To race, try to spend more time at lower heart rates so you can last longer

Interesting question. The answer, as I see it, is basically "Yes".

I've plugged a couple of different scenarios into the Calories and Watts Calculator included with my CycliStats program, and here's what I come up with:

Assume a ride of 50 miles, over "Rolling" terrain (1800 feet of climbing).

Riding at 15 mph would burn 1772 total calories - 35.4 calories per mile, or 531.6 calories per hour.

Riding the same route at 20 mph would burn 2397 total calories (35% more) - 47.9 calories per mile, or 958.8 calories per hour.

The reason, as suggested in an earlier post, is that air resistance increases exponentially as speed increases.

FWIW, I drove my WRX across Nevada a few years ago on Hwy 50 (the Loneliest Road in America), and probably averaged close to 100 for most of the route (and got up to 140 briefly, until I started thinking about blowouts, and unfenced cattle :eek: ). The gas mileage suffered, but it sure was fun!

I am looking at a steady pace like a TT so that the senerio of caloric consumption is easier to understand.

Jake,
We are talking fuel/caloric consumptions at 2 different intensities. Easy terms are that you burn less calories at lower intensities then you do at higher. How you go about your periodization schedule is more involved then just the calorie question. Take for instance if you only have 1 hour a day to train for fitness- on a given day at what intensities do you get the most bang for your buck in CV, caloric burn and neuromuscular training? Simply put -as hard as you reasonably can without hurting yourself or defeating yourself psychologically or where it takes longer to recover and you lose all the benefit of your training.
Velocity