What is the main factor in caloric expenditure?

What determines how many calories you burn when you perform an activity? Is it the total work done? The exertion level? The mechanical work done by your muscles?

Say your goal is fat loss. You’re a good biker but a bad jogger. Is your best bet to do a lot of biking (since you can perform more work that way) or to jog (since it’s more difficult)?

Is there a break point (for lack of a better word) were your body starts burning off far more calories because it’s using a different metabolic pathway?


Hey Zulu,
I definitely am not a scientist, but your own body weight, ground incline and perceived level of exertion(as opposed to heart rate) method all have a significant impact on expenditure. I think the more “compound” the movements (weights or otherwise) as well the more calories burned.
I like to focus more on the sprint distances, than standard “cardio” distances.
Just some thoughts.

Oxygen Consumption.

More on this later.

The amount of oxygen consumed, which can be directly measured using a metabolic cart, is the main factor in determing caloric expenditure.

So, why don’t we all just hyperventilate and take in massive amounts of oxygen?

Oxygen Consumption refers to the oxygen that is actually taken up by the tissues and used for metabolic purposes. So, to increase oxygen consumption, you have to increase metabolic activity.

Increasing the amount of muscle mass used will increase oxygen consumption. Technique is important in many instances. For example, a successful cyclist activates his glutes and hamstrings, as well as his quads, during each downstroke, whereas a novice uses mainly his quads. Distribution of work and power in the former case allows the successful cyclist to go at a higher work rate with less muscular stress at the same oxygen consumption.

Also of note is that not only the oxygen consumed during an activity/exercise should be considered, but also the oxygen consumed after the activity/exercise due to the activity/exercise itself. That is, when weight training or performing high-intensity intervals, one has an elevated oxygen consumption at rest–relative to basal conditions–that is known as Excess Post-Exercise Oxygen Consumption.

just typed a big spiel and the forum ate it, (dont worry it was low in both fats and carbs), cant be assed writing it again…

Thanks Timbo! What practical applications would stem from this knowledge?

In my example: cycling would be the better alternative?


Timbo, does weight training have a post-exercise effect because it obstructs the flow of oxygen during a set? Thanks, Brian


Great question–I apologize for the delay in response…I haven’t gotten past the first page of posts in a while:-)

EPOC following exhaustive exercise–usually measured after aerobic/anaerobic exercise–has the following components:

  1. Resynthesis of ATP and PCr
  2. Resynthesis of lactate to glycogen (i.e. Cori Cycle)
  3. Oxidation of lactate in energy metabolism
  4. Restoration of oxygen to myoglobin (i.e. the muscle’s equivalent to hemoglobin) and blood
  5. Thermogenic effects of elevated core temperature
  6. Thermogenic effects of hormones (i.e. catecholamines)
  7. Effects of elevated heart rate, ventilation, and other elevated physiological functions