Friday, July 18, 2008

Lactate Threshold and VO2 Max Tests

This is no fun at all!

Today (July 18) I did a lactate threshold (LT) and a VO2Max test at the Carmichael Training Systems (CTS) office in Colorado Springs. With just a few weeks to go before the cross country ride it was time to see where my conditioning really was and make adjustments. The tests results were somewhat surprising.

First was the LT test. The point of this test is to determine when the body is producing more lactic acid than it can process. I am sure I read once it is the point where you are burning only carbohydrates instead of a mix of carbos and fat but I can't find that source. Certainly once you do pass LT you are riding on borrowed time.

To do the test you warm up then a blood sample is taken by pricking a finger to get a baseline. Then they put nose clips on you, a breathing apparatus in your mouth, and you start riding. The computer controls the amount of wattage you produce and it steps it up 25 watts every three minutes. Every step another blood sample is taken and that gets pretty annoying. Can't complain because of the breathing mouth piece.

I hit LT at 225 watts and a heart rate of 157 bpm. I am surprised that the LT HR is that low. I have been doing a lot of work with my HR between 163-167 especially in Memphis. Part of the explanation is altitude. Colorado Springs is at 7,000 ft and Memphis is 300 feet. It also partly explains why I have to work so hard to do tempos in Boulder at 5,000 feet. Still, I couldn't get an explanation that I understood for the LT especially when the VO2 Max test results are considered.
David Twynam has his own opinion of the LT test. "I've never been convinced by the value of an LT test. People buffer lactate at different rates so what 4 mmol/l could be quite tolerable for subject A whilst it could be completely unsustainable for subject B. An inflexion point analysis is so dependent upon ramp rate. I much prefer the notion of a functional threshold power, defined simply as the highest power output that can be sustained for an hour, and basing training power zones as a percentage of FTP. And another advantage is that you can do this test without the blood letting. On the other hand the VO2max test does seem useful to me, although I proxy the procedure now with a 5 minute all-out power test on my bike without O2 and CO2 measurements. When I had my VO2max test they testers analyzed my data and estimated my ventrilatory threshold, which they said should correspond very nicely with my functional threshold, which indeed it did."
The VO2 Max test determines the amount of oxygen your body can utilize at maximum effort. The test is largely the same as the LT test except that no blood is taken and the computer works the wattage up to exhaustion. My VO2 Max score was 47.4 ml/kg/min which is very, very good. Considering that I haven't done any exercises to drive that up, I was very pleased.
The conclusions reached by Mike Durner (that his him in the picture) is that my tempo and steady state wattage targets for altitude need to be lowered, that I have to have different targets for Memphis versus Colorado, and that I still have a lot of potential to improve.

1 comment:

Anonymous said...

you need to check out
I can't possibly explain to you how good they are at metabolic testing.
Myself and what is now 4 others on my team alone have switched to SportsLab (also here in Colorado Springs).