Thread: What is my LT?
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Old 07-22-07, 05:01 PM
  #23  
asgelle
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Originally Posted by Snicklefritz View Post
What a couple of people are pointing out (in response to orca) is that if you want to get really technical then no you don't measure LT by looking at power. You measure LT by looking at blood lactate...but power can be used as a manifestation of what's going on with lactate content. Ergometer isn't the key point in some of the earlier comments
As Squint pointed out above, lactate concentration is the dependent and intensity (power) is the independent variable. Power is not a manifestation of blood lactate concentration; it is the cause. There are many responses to exercise intensity including blood lactate concentration and heart rate, but there are many more such as core and skin temperature, respiration rate, and perspiration rate. Any of these can be used to study the body's response to exercise, but only lactate concentration can be used to determine lactate threshold (by definition). The independent variable can also be expressed in different ways: power, pace, VO2; but unlike the dependent variables mentioned above, these are not distinct. They are just different ways of expressing the same intensity.

Lactate threshold is defined as the point at which the independent variable (intensity, power) elicits a predetermined value of the dependent variable. So while saying I'm using 4 mmol/l as my value for the dependent variable at LT defines how I'm setting LT, that number has no value alone in evaluating an individual as everyone will have LT at 4 mmol/l. What is important is the value of the independent variable which causes that value, say 300 W.
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