Derny Driver wrote:Tim wrote:
My lactate threshold is about 82- 84% of my max heart rate. I know this from basic 40km time trialing at maximum effort.
Hmmmm
My lactate threshold was 92% of max.
You're sort of both right - mainly because the concept of threshold is a bit fuzzy and with many definitions.
Lactate Threshold is not a measure of heart rate, so that can add to the confusion.
LT is a measure of the power output at which blood lactate levels rise up 1 mmol/l above baseline values (typically to ~2.x mmol/l) during testing under a specific protocol. This corresponds to an intensity that a fit rider could sustain for several hours and is typically 10-15% lower power than what one might sustain during say a time trial of say 25-40km. Accordingly, the HR one experiences at LT will be somewhat lower than what one would experience for a TT. At the LT power level, cardiac drift may or may not occur, depending of duration, fatigue and fitness level and other factors like hydration, heat etc.
Threshold in the sense that many use it (e.g. Functional Threshold Power), a level that most cyclists equate to a sensation of "threshold" equates to a power/effort level that one could sustain for ~40-60 minutes or thereabouts or say a 40km TT. In a blood lactate sense, it's also a level know as Maximal Lactate Steady State and blood lactate levels during such an effort are often much higher than at LT, anything from 3 to 8 mmol/l and sometiems higher (varies significantly by individual). HR during such efforts is not static but will be within a band (88-93% of MHR is pretty normal). Cardiac drift is typical during such an effort level and HR can be lower than range to begin with and go above range during latter stages. If HR remains constant during such an effort, it's likely that power is gradually falling.
