Lactate Threshold Test on the Bike

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2006-06-08 1:15 PM

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Subject: Lactate Threshold Test on the Bike
Hello,

This morning I attempted to do a Lactate Threshold test on the bike and I'm a little confused by the results. First off, I live in Los Angeles so I did the LT test on the safest place I know where I can ride for over 20 minutes without stopping. I warmed up and then started the test on a 5 mile hill climb that climbs a 1,000 ft. The hill gets steeper as one gets to the top. As required by the test I had absolutely nothing left in the tank at the end buy my HR was definitely spiking at the end of the effort not leveling off as I would have expected.

For example, my average heart rate varies greatly depending on what time section you look at:
last 20 minutes: 163.2
last 10 minutes: 166.5
last 5 minutes: 168.3
last 3 minutes: 169.3

The test procedure calls for looking at the last 20 minutes of the test but that is more than 5 beats per minute lower than what I averaged over the last 5 minutes of the test. What gives? Which of these numbers, if any, are my lactate threshold?

Any thoughts on the results or my testing procedure would be appreciated.

Thanks,
Mike

2006-06-08 1:18 PM
in reply to: #447724

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Champion
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Subject: RE: Lactate Threshold Test on the Bike

I had the same phenomenon when I test my LT for running.  I was told that it's normal to spike as you get more and more tired, and that's why they have you take an avg of the whole 20 minutes.

But I'm curious to see what others think as well. 

2006-06-08 1:22 PM
in reply to: #447724

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Subject: RE: Lactate Threshold Test on the Bike

I would think your results would be more accurate on a flat course.

2006-06-08 1:33 PM
in reply to: #447743

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Veteran
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Los Angeles, CA
Subject: RE: Lactate Threshold Test on the Bike
When I saw the results I thought that the course may be the answer but before setting out on the test I didn't think it would matter and as I sit here now I'm still not sure why it would matter.

I was going as fast as I could the entire time and this particular climb is not flat or downhill in any part (until of course you turn around and go back down) so there are no unusual dips in my heart rate.

Thanks for the help.

Mike

2006-06-08 1:35 PM
in reply to: #447724

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Subject: RE: Lactate Threshold Test on the Bike

Generally, it is best to do the test on a flat section where it is easier to keep your effort level constant.  The key to executing the test well is to find an effort level that you can hold for 30min, but no longer.

But your HR will drift up over the test, so the last 20min is still the way to go.  If you're not satisfied with the results, you could always re-test--more fun!

2006-06-08 2:45 PM
in reply to: #447724

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Subject: RE: Lactate Threshold Test on the Bike
Although the test is best done on a flat course, I would say that if you've kept your effort consistent throughout, that you have a reasonable estimate of your LT at 163.

You will see your HR creep up due to a number of factors including:

1) fatigue
2) pacing (if it's the first time doing the test, it's hard to find a good pace)
3) time remaining - it's significantly easier to pour it on for the last two minutes than it is with 20' to go - therefore as you get closer to the end you will tend to work a little harder.

Don't worry if the number turns out to be a little low - you will discover this on subsequent tests and be able to adjust accordingly. Better in the early stages to go too easy than too hard.

Shane

2006-06-08 3:17 PM
in reply to: #447866

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Subject: RE: Lactate Threshold Test on the Bike
gsmacleod - 2006-06-08 12:45 PM

Although the test is best done on a flat course, I would say that if you've kept your effort consistent throughout, that you have a reasonable estimate of your LT at 163.


I'm no expert, but I agree with Shane. If you have maintained a consistent effort throughout the test, it should be reasonably accurate, regardless of whether the course was flat or uphill. The key is that the effort needs to be consistent...that is why training with a power-meter can be so beneficial. I suspect it is also why the test is best done on a flat course, or on a long gradual climb -- because it is easier to maintain a consistent effort on that type of course than on one with rolling hills or with a steeper climb at the end.

One question: Did you do a warm-up and then ride a 30-minute TT (taking your average HR over the last 20 minutes) or did you do a warm-up and then ride a 20-minute TT?
2006-06-08 3:32 PM
in reply to: #447724


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Subject: RE: Lactate Threshold Test on the Bike
as others said, you should test on a flat course.

that being said, LT tests are all-out tests, and thus you HR should be higher (in my book, possibly even approaching your max HR) at the end of your test. otherwise, you weren't going all out. the average for the whole 20 minutes will obviously be less than you ending HR or even your average HR for the last 3 minutes because you cannot sustain that higher HR for the whole 20 minute test...
2006-06-08 4:36 PM
in reply to: #447762

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Subject: RE: Lactate Threshold Test on the Bike

True.  There isn't any reason why you couldn't test on a hill BUT that makes it more difficult to determine if you are holding a steady effort.  I like using the trainer for LT testing because you can more or less hold everything constant without any external factors.  Of course you don't race on a trainer so there will be the people who say it isn't representative  but I personally think it is better than most of us are able to manage outside unless you have a nice flat closed TT course or 10mile stretch of flat road without any traffic, stop sign, or lights.

JohnnyKay - 2006-06-08 2:35 PM

Generally, it is best to do the test on a flat section where it is easier to keep your effort level constant. The key to executing the test well is to find an effort level that you can hold for 30min, but no longer.

But your HR will drift up over the test, so the last 20min is still the way to go. If you're not satisfied with the results, you could always re-test--more fun!

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