BTW I don't have a particular affinity to whether a threshold exists or not in terms of lab data - Noakes says no, others say yes. I just think its time people stopped claiming that "FTP" is some kind of special intensity where you can naturally pedal away until the cows come home and its so absolutely noticeable that almost any rider can ride at it on demand.. All intensities have the same features and any rider can ride at 10 pace, 25 pace or 50 pace on demand and get it roughly right every time - they are not likely to get 25 pace more right than 50 pace or 10 pace and AC's quoted study above where he claims this is demonstrated - it absolutely does not demonstrate this whatsoever since they only tested one intensity - other intensities would have given the same finding.

Functional Threshold Power is an estimate of the point where we transition from using a mix of carbohydrate and fat to solely using our finite CHO stores. This point is observable when doing ramp tests or the MLSS test.

MLSS is better estimate of this true threshold point than a ramp test although you can observe the transition using lactate, heart rate, NIRS, and expired gas analysis.

Because of the issues with performing ramp tests, where we see a lot of guessing where the inflection point is, if not obvious, and the challenge that performing tests in the lab is not specific to where we actually perform. Plus, the costs and logistics of doing lab test. Also, our physiology changes very rapidly, so, metrics determined from a test have a very short period of usefulness.

So we estimate threshold power from data from the bike in the field. Not just the FTP, but peak power (PMAX), sprint power (PMAX/FRC), track time trial power (FRC), track pursuit power (FRC/FTP) and time trial power (FTP) and long term power (Stamina). To help us plan our training and to teach riders to learn what performance at a given level looks like.

No, it is not misleading, as it is an accurate description of reality.

Again, try sustaining a power measurably above vs. below your FTP for as long as you can, then report back to everyone here.

<offending remark in response removed - apology noted>

Functional Threshold Power is an estimate of the point where we transition from using a mix of carbohydrate and fat to solely using our finite CHO stores. This point is observable when doing ramp tests or the MLSS test.

Difficult question to explicitly answer, since substrate oxidation also depends on diet, duration, etc. Hyperventilation at high exercise intensities can also undermine the validity of RER as a quantitative measure of fat vs. carbohydrate oxidation.

That said, some studies have indeed use RER = 1.00 to estimate "threshold" during incremental exercise tests, just as Hamish indicated (although at the same time, many years ago Larry Spriet published data showing mobilization of IMTG stores even during intense electrical stimulation of isolated rat muscle).

TL; DR: As with all such things, it's complicated. If you are only interested in getting faster, it's probably best to ignore such details and just get on with your training.

If I could simply train all the time....that's what I'd do, and I wouldn't be on ST much. Unfortunately, recovery leaves lots of time for pondering these things--and, I like understanding things. At 50 I seem to have more recovery time. I'm okay with complicated...I'm also ok with "in general <blah blah blah>, but there are lots of variations."

RER=??

IMTG = intra-muscular triglycerides?

ETA: I'm also ok with a pointer to a few studies that you think validly demonstrate the situation.