This is what happens when you go for one of these tests as a runner. You fill out an extensive questionnaire on health and activity levels (mine indicated a prolonged absence from running but fairly regular cycling and gym workouts) and then you are given time to stretch and warm up. Once you are on the treadmill they put on a heart rate strap (I brought my own), attach a breathing apparatus and plug your nose so you can only breath through your mouth. The treadmill starts at a low speed and every 3 minutes the speed is increased. Just before each speed increase you offer your hand up for a blood prick and they take a sample (my finger was rather sore at the end). When you feel fatigued and are considering quitting you wave your hands, otherwise you give the thumbs up at each interval. Once you want to quit you simply step off on the sides of the treadmill. My lab tech encouraged me to keep going once I waved my hands, but I was ready to quit. Originally I had dreams of shattering records (it's hard to check your ego at these things right?) but reality quickly sets in when the air is harder to push and you know a speed increase is coming. Oddly, since I had barely been running, running quickly on the treadmill felt fantastic. A week after the test they had my results and since I didn't live locally I had a Skype interview with them to go over my results.
Previous to this test my only VO2 indicator was from my Garmin watch which told me my number was 64 but this measure would have been derived from heart rate only at various paces in relation to my age. VO2 max is a measure of maximal oxygen uptake. It's an indication of performance potential for endurance athletes as it predicts their efficient use of the aerobic energy system. Generally the higher the number, the longer the athlete should be able to output energy continuously for an endurance event. VO2 max is a poor predictor of maximal speed or power, it's only a predictor of how long you can continue putting out effort while using the aerobic energy system. The table below shows VO2 ratings for the general population so you can compare your rating to a larger number of people. While my Garmin # was likely a best guess, it was also my highest number obtained during peak fitness. During this assessment my rating was 56.1 ml/kg/min. I'm 44 years old so my rating is "superior" as compared to the general population but not to get over excited you can look up various athlete scores ranging from numbers similar to mine to 96 ml/kg/min for the best cross country skiers on the planet.
Training zones were ultimately the weakest part of this test for me. Generally the paces they advised me to run for greatest overall fitness improvement (zone 1) were much too slow for me to even jog comfortably (6:00 to 7:04 min/km) and I'm unsure if they were wrong or if my ego won't allow me to jog that slowly. I do find running much slower than 5:30 min/km pace to be awkward and uncomfortable on the road. While I don't discount the results entirely (remember this is my body untrained) I'm not sure if the result is completely accurate as my perceived easy pace is 30-45 seconds per km faster than what was prescribed. Either way, it served as a good reminder that I don't run enough of my runs in an easy manner, as most of us endurance athletes are guilty of. This is something I plan to address this summer while training for the Victoria Marathon. I do find the 6:00 - 7:00 min/km (or slower) pace easy to maintain while trail running so possibly that is a good way to stay within their zone 1 measure.
If you're considering a fitness assessment similar to this one I'd recommend getting tested just before you start a new training block, then again near the end of that block before your key event. This will help establish training zones and give you a base measure to compare to your end result for fitness. Your test before your event would be helpful for determining exact fuel requirements. If you have the discretionary money a mid training block assessment would have value to gauge your reaction to training. I don't recall what I paid for my discounted test (check out your local race expo's for deals!) but the listed rate on the website is $195 for one test. I believe they offer discounts for recurring test packages and even for coaching or training plans. The Skype interview was useful and informative so if you do get tested don't skip the consultation after your test.