Good question. I’ll give you the longer answer but will miss something(s) and likely not answer your question at all!!
I started testing to see if it mattered and would guide my training. As world turns, I became less interested in racing and peak race performance (I do mostly TT’s 10-25 miles) but remained interested in if lactate data was useful and how it moved around. Some friends wanted data as well. So we set down a path. Covid derailed the group work, but I kept testing myself just to accumulate data.
I haven’t worried about exactly what happens at LT1 in the muscles or with sugars and fat. What I noted from some coaching programs was that LT1 had received good attention as a target for training and it was lower power number than what I would normally do for “tempo”, but higher than what I would do for easy endurance.
So armed with a thought that LT1 might be a productive target to spend time in, knowledge of what my LT1 was (lactate testing definition) , I set out to accumulate a number of hours in this range as my “Z2” or endurance ride target. Along with the LT1 time, I threw in some “stuff”. Stuff turned out to be 15-25% of time between 90-100% of FTP. Specifically, I find that 90% FTP power target to be very productive.
What I found over a season was targeting that LT1 zone plus adding some stuff worked well for me. My LT1 shifted from 165w up to 200w (about 4-5 months of training) and my MLSS moved up from about 220 to 230 and with lower RPE (mental matters too). I also ran a 10 mile TT for friends every other week. So I was getting Lactate data, power data, RPE data and testing performance over ten mile race-like efforts.
My conclusion was that having LT1 and modifying my training worked pretty well. I did not reach all time career peaks, but I reached a high level of fitness and was very happy mentally as I enjoyed the training block and was having a lot of fun riding.
Did I need LT1 and lactate blood tests to get there? Definitely not, but it was fun to have the numbers.
I was somewhat surprised how my LT1 shifted to a higher and higher % of FTP. If I was guiding based on FTP I’d have undershot LT1 target as I gained fitness.
Agree that finding that Z2 training sweet spot is a useful concept. It will definitely move up with training and it will not be a constant fraction of FTP or MLSS (from what I can see in my data).
Thinking about how many folks train, we see the “twice a week hard” concept frequently. Or 80:20 or some other variation on the theme. I wonder if the twice a week hard part is less important than how we use the remaining time. I think, but can’t prove, that my focus on keeping the 80% productive with an LT1 focus worked better than worrying about the 20% That might sound backward but pretty sure it worked.
Nobody asked… but looking at the thread subject… I have not found LT2 to be useful
I have found lactate testing, FTP testing and MLSS testing to be useful. Some riders have a big disconnect between MLSS and RPE. They think they are maxed but aren’t even close. RPE has a massive effect on FTP testing. But MLSS and Lactate testing don’t lie and don’t care what your RPE is. So for riders under performing, a biomarker test (Lactate) can help them break through.
Happy to dialog on this topic. I’ve tried to use the data in simple ways more than think about the physiology. But both are of interest.
And longer then 20min