Breaking the Wall

putting aside the calculators, there is an element of truth to what you found as there have been studies performed that found that in addition to the linear increase of VO2 to increase in velocity, there is also a relationship between ml/kg/km of O2 used during running. These studies found that at constant speeds the amount of O2 used per km of running was constant whether or not the individual was running fast or slow.

The elite Africans seem to be getting numbers in the 190-200ml range on average, with Zerseny Tadesse being recorded at about 150ml of O2 per kg/km which is the lowest ever recorded level of O2 used.

What I think that the studies are leaving out is that they are trying to use O2 consumption to calculate metabolic cost, when it is apparent that VO2 is not the only factor in play. So, while VO2 use per km may remain constant at different velocities it does not mean that metabolic cost reacts in an equivalent fashion.

Using Tadesse as an example supports this, as with his VO2 max in the 80's, and a ml/kg/km of O2 consumption in the 150's, he should be able to run a marathon in under 2 hours if he is able to run the full marathon at a level equivalent to what his O2 numbers tell us. We know that this is very far from the case as he has never to my knowledge broken 2:12:00 in the marathon and has dropped out on a number of occasions.

So, I think that the calculators are simply trying to give the best estimate that they can with the knowledge that we currently have. The problem is that we don't know exactly what determines the metabolic cost of running or how much it "costs" to run a mile in 6:00 vs. 10:00. All we know is that the amount of oxygen used to run the distance is approximately the same even when practically disregarding the velocity we are running at.

Jeff:

Do you know if anybody has tried to measure the mechanical energy required to run? This should be fairly simple if you have a treadmill with force plates. You can get the work against ground from the ground reaction forces, and assume that the work in the air is a small constant fraction of that.

Rodger Kram up at the University of Colorado has done a lot of work with energy cost of running, and has an Alter-G treadmill that he built force plates into. The focus of his research is looking into the energy cost of locomotion (walking, running, etc.). He has even done research with animals (from elephants to bugs) to compare their energy cost to that of humans. I would look him up first and then branch out from there.

I believe that some other researchers figured out a way to determine caloric cost of running as well, although I do not recall their methods. That would be something to look at as well.

Here is a word doc of a study called "The Effects of Running Speed on the Metabolic and mechanical Energy Costs of Running" in the Journal of Physiology Online.

This study suggests that the metabolic cost per distance remains relatively constant across running speeds while mechanical cost per distance decreases as speed increases.

http://www.google.com/url?sa=t&source=web&cd=1&ved=0CBoQFjAA&url=http%3A%2F%2Ffaculty.css.edu%2Ftboone2%2Fasep%2FHarris.doc&rct=j&q=THE%20EFFECTS%20OF%20RUNNING%20SPEED%20ON%20THE%20METABOLIC%20AND%20MECHANICAL%20ENERGY%20COSTS%20OF%20RUNNING&ei=QRGWTvbrKJTjsQKD15jwAQ&usg=AFQjCNF1BpcxNPnyMp-Fgd_mZUcSom4d9g&cad=rja

Interesting article. I would be interested to see if someone has performed a similar study at faster speeds. The runners in this study had 10k times ranging from 29:30-36:00 yet their running speed ranged from about 11:30-6:40 per mile. The runners told researchers that the two fastest speeds (3.67m/s and 4.00m/s) felt the most comfortable, but those are also the speeds that were the closest to the speeds that most of the runners trained at. Would mechanical cost for these runners climb as they started to run at speeds that were not so easy?