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done a lab test on my bike today and compared it with 6 months ago
tests were done measuring lactate from my ear and measuring CO2+O2 with a mask. stepping up 30W every 2mins.
from a lactate point of view, the curve was higher by 30W
but the "ventilatory threshold" did not change a single watt. this number is assumed by the local experts in the lab the "max 30mins sustainable wattage"
how can this be?
is it possible you improved a lot from a lactate point of view but no improvements in your ventilatory threshold???
is it correct to approximate your FTP value from 4.0 mmol intersection on the lactate curve?
While i'm not going into the discussion of why VT2 remains unchanged while power at 4 mmol did, I can answer your last question: No, it's nbot a correct approximate. Power at 4 mmol is power at 4 mmol. Your FTP is your FTP. They can be very close or not so close. 4 mmol is a blanket statement and is not necessarily reflective of any threshold for you (except the 4 mmol threshold?).
Some people can suffer better. And, I assume, not everybody's lactate runs away at exactly 4mmol.
There's a few things at play here.
FTP is like a car's performance. How fast does it go down the 1/4 mile...
You can look at many things to help determine what that might be, say the horsepower or the cylinder displacement.
And, you can correctly assume that a car with higher horsepower is probably going to be faster. But, there is potential for that to be misrepresentative... What's the weight of the car, can the tires handle the power to the track etc etc. Can the driver drive to the car's performance level etc.
That's where VT, Lactate threshold, OBLA etc related to Performance / FTP.
With that said, In my opinion (Which is quite practiced), 30 watt stages every 2 minutes will most likely over-estimate a workload at 4mmol. IE if the stages were longer or smaller jumps, the power output at 4mmols would be less.
The above poster is a physiologist employed by PEARL iZUMi. However, statements are not made on behalf of nor reflective of PEARL iZUMI in any manner... unless they're good, then they count.
"FTP" and 4 mmols of lactate have nothing to do with each other. I would not use 4 mmol to estimate anything really - in this test all it indicates is your current wattage output @ 4 mmol during a 2 min graded exercise test.
Misconceptions about some determination of "lactate threshold" is that it is equivalent to 4 mmol and/or "ventilatory threshold"- it's just simply not the case. 4 mmol and/or ventilatory threshold is certainly not "max 30 minutes sustainable wattage" in all athletes/humans.
Equal work capacity limits at various power or energy outputs is common assumption with use of "lactate threshold", FTP, and even VO2 max testing. The typical application of this data is that everyone's work capacity at various percentages of those data points is the same. Assume nothing- tons of people can't even sustain 10 watts for 30 minutes let alone 30 min @ 4 mmol- this is an individual capacity issue and can be trained but short sighted to assume everyone's capacity is the same at 4 mmol or any other percentage of work output is the same.
I am not exactly sure which protocol they used in your test but most tests will stop at "lactate threshold" or 4 mmol. When using lactate as a metric of looking at an individual's work output or changes in fitness, it is important to measure current physiological range of that athlete.
Today, 4 mmol can be 100% of your physiological range but 6 months ago when you tested 4 mmol could have been 25% of your physiological range. So, depending on this one data point, 4 mmol, as your reference point will simply not give you the answers you are looking for in terms of understanding your current physiology and fitness levels. An individual's physiological range can be very dynamic and needs to be considered when using any lactate data for evaluating performance changes.
I suggest figuring out why are you using these tests, which ones are most relevant to your training/performance objectives, and how is the test influencing your training plan/decisions to improve your performance :)
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: Jul 17, 17 19:57