Someone on the ride yesterday asked me about the difference between VO2 max and anaerobic threshold.
VO2 max is the maximal volume of oxygen (expressed in mililiters of oxygen) the body can consume (expressed per kilogram of body weight) in one minute. I was tested at De Anza College in Cupertino at 69 mililiters of oxygen consumed per kilogram of body weight per minute. A good number yes, a great number no. The average person will test around 45 mlO2/Kg/min. World class athletes test above 80 (Lance is well over 80) and the highest numbers are in the low 90's.
Anaerobic threshold (AT) is the percentage of your VO2 max that can be sustained for longer than 10 seconds. You have several types of AT. There is the AT you can sustain for short efforts (longer than one minute but no less than three minutes), short medium efforts (three to six minutes), medium efforts (six to 15 minutes), and long efforts (15 minutes plus). A normal AT might be 60%, that is when a person is at 60% of their max effort they are comfortable (not like lying on the couch watching TV) and can maintan that effort for some time without building up more lactic acid than their body can eliminate. But if that person increases their effort by just a few percentage points, they become anaerobic (building up more lactic acid than the body can eliminate) and eventually slow down.
Using the redline of your car's tachometer as your VO2 max, the anaerobic threshold is the yellow line of your car's tachometer. The redline is the max (yes I know a car can rev higher than that but not without damage) and the yellow line is the point where it is time to shift gears.
Your VO2 max is determined mostly by genetics and training does increase it some but the real change in your body that comes with hard interval training is an increase in your AT level. You still suffer and hurt but you can keep up the pace for some time. My brother Daryl was tested at the Olympic Training Center in Colorado Springs when he was on the junior development team. Daryl's VO2 was good (and I don't remember the exact number) but his anaerobic threshold was excellent. He could maintain an effort that was 90% of his VO2 max and he could produce a blood lactic acid level of 18 milimoles per liter, the highest ever recorded at that time (1986 or so). Most people can produce 5 or 6 milimoles of lactic acid per minute.
Anaerobic threshold is best trained by some form of interval training. Structured interval training is picking a distance and a rest time and repeating it. Hills make for good intervals because it is easy to get the heart rate up without going very fast and the downhills make for a perfect recovery. Unstructured interval training is what happens on a group ride like the Saturday or Sunday ride. There are sections of the ride you know in advance will be hard and other times where anything can happen. I think a mixture of both is good. Structured intervals like hill repeats and group rides that prepare you for riding with 60+ other riders at race speed. It is important to be comfortable in a group without wasting alot of effort and to know when it is important to be in the first 10-15 and when it is not.