Training & Nutrition - VO2 Test on Bike, CycleOps, or Treadmill?

I had my VO2 tested on my bike in Dec. which got my boyfriend curious where his level was, so I bought him one for x-mas. The tester gives you an option to do the test on any of the three listed in the title. I am training to race and he joins me for the weight sessions, does two spin classes a week, and he will run on the treadmill once or twice a week as well but hates it and usually can't run more than 30 minutes. He did the MS150 last August without much trouble. He has upped his cardio considerably in hopes to make this spring/summers cycling with me easier, he only lifted weights last year until he bought his bike in May.

I asked him if he was taking his bike for the test and he said no. Wouldn't this be better to test on than the others given that will be his primary cardio? If you have any scientific references or articles speaking to this I would appreciate help, he is scheduled for the test at the end of the week. Thanks!

...to avoid any confusion the CycleOps is the stationary kind with toe cages.

Are you talking about ergometers? those devices that can be fitted on exercise bikes and measure your effort level while exercising? I'm thinking of getting one for my birthday too and found this guide (http://pickyguide.com/sports_and_recreation/exercise_bikes_guide.html) useful

I think he should do it on the treadmill. You only need to warm up a bit, and then the tester will up the incline every minute or so. I know of a really good guy who does it in Madtown, former member of the Russian XC ski team.

If you're going to go to the trouble of getting VO2peak tested, I suggest doing it with your primary activity. if he bikes a lot, test on the bike (or the CycleOps, which will give useful power readings).