Posted by Dave on July 1, 2011 | 4 CommentsOne of the first books site consulting expert Travis Saunders suggested I read while preparing for this site was Tim Noakes’ legendary tome, Lore of Running. It’s a massive, almost encyclopedic volume, filled with Noakes’ incisive analysis of scientific research into running performance. Many academics value it for its references alone, which are available for free online (a hundred pages of double-column, tiny-font text). It’s too much to take in all at once, so I’m going to read it slowly over the course of the summer, giving you the highlights as I go.
This week’s topic: VO2 max (technically it’s “vee-dot-oh-two max”—the V should have a dot over it and the 2 should be subscripted, but that’s tough to do on a blog). VO2 max has been elevated among certain runners to the level of midi-chlorians among Star Wars buffs. Just as Jedi with more midi-chlorians are strongest, endurance runners with higher VO2 max values are supposed to be nearly universally better than runners with lower values. As it turns out, in Star Wars and in running, things are more complicated than that.
So what exactly is VO2 max?
Noakes actually starts the book by explaining how muscles work. I won’t go into details there; suffice it to say that the key to muscle performance is delivery of oxygenated blood to the muscles, and adequate fuel to produce energy. Oxygenated blood comes from the lungs, and is pumped by the heart, which is itself a muscle requiring its own supply of oxygenated blood.
VO2 max can be seen as the maximum performance of this system: the amount of oxygen that can be effectively delivered to the body in a given time period. It is usually measured by having a runner breathe through a face mask while running on a treadmill so that the volume of oxygen consumed can be measured. Every minute or so, the workload of the treadmill is increased, either by increasing speed or slope. The runner keeps running until she is exhausted, and the typical results look something like this:
As the workout gets harder, initially the runner is able to use more and more oxygen, but at a certain point, the volume of oxygen used stops increasing. Runners can continue for a few minutes, but since the workout keeps getting harder and they’re getting no more oxygen than before, they are soon exhausted. This is fine, because we already have the number we’re looking for and they’re free to head to the nearest bar to rehydrate (albeit inefficiently) with a cold beer.
While you can increase your VO2 max by 15 percent or so through training, it’s believed that some individuals simply have a genetic makeup that gives them a higher VO2 max than others. If your VO2 max is, say, 50 (typical for a fit young man), this line of reasoning posits, you’ll never be able to run a marathon as fast as Paula Radcliffe (70) or ride up L’Alpe d’Huez as fast as Lance Armstrong (85).
So why does the volume of oxygen consumed max out? Shouldn’t the body be able to keep on going harder and harder until the runner is exhausted? There must be something limiting our ability to consume oxygen, and researchers initially focused on the muscles and the heart. It could be that there’s a physical limit to how much oxygen each person’s muscles can use in a given time. Or it could be that the at some point the heart isn’t getting enough oxygen from the coronary arteries. As it turns out, it’s likely that the brain limits the heart rate before either of these limits are reached. An unconscious “central controller” is what’s responsible for maxing out the rate at which oxygenated blood is delivered to the body. This is probably a good thing, because otherwise simply getting exhausted could come in the form of heart attack, heat stroke, or worse.
So if VO2 max is so important to endurance running performance, why do we even bother running races? We could just measure VO2 max and be done with it, right?
As it turns out, VO2 max isn’t a perfect predictor of running performance. It’s important, to be sure, but some runners are simply more efficient than others. If Jill is 15% more efficient than Joe but Joe has a 15% higher VO2 max, then these values should even out and their performances should be equal. If Jill is 20% more efficient, she’ll be faster despite her lower VO2max. Cavin Woodward of the UK had a VO2 max of 74.2, virtually the equivalent of Alberto Salazar’s 76.0, but Salazar could run a 2:08 marathon while the best Woodward could manage was 2:19:50. The difference is due to Salazar’s superior running efficiency.
When Salazar (at the peak of his career) runs at his VO2 max, he’s going faster than Woodward can while running at his VO2 max. VO2 max is important, and without a sufficiently high VO2 max, you’re never going to be among the elite athletes of the world, but efficient running is equally important—and possibly more so, because it may be easier to improve your efficiency than it is to improve your VO2 max.
How do you increase running efficiency? We’ll have to save that discussion for next week.