Originally Posted by
couldwheels
I actually keep just before I get soreness. Lactic threshold, is it? I throw in short intervals where my legs feel the burn and then back off a little bit to recover but keeping above z3 effort.
It does have something to do with fit. If I lower my seat (too low setting), I feel the burn sooner even at lower cadence. I doubt I'm making more power because the seat is set too low.
At the correct seat height, my legs is bent significantly more at the top of the stroke with 170 mm. There's a difference of 40mm the top pedal distance between 170 and 150mm cranks.
The feel is almost similar to setting your seat too low if using 170mm at the correct seat height compared to 150mm.
Most of that is just training effect. You get better at what you do. It's hard to tell what's going on when one switches back and forth. The best is simply to get one's numbers, i.e. crank/leg proportions, knee angle at top and bottom, and hip angle at the top, hands on hoods. Any bike fitter can help you get those angles in line with what works best. Then you train using that fit. There are bike fit contraptions used by a few fitters where the fitter can change all the elements of a fit and see with which fit a rider can produce the most power at some single heart rate. However that doesn't really work because it doesn't take efficiency into account, i.e. will that fit still be faster after 3 hours of steady hard riding? It's complicated.
I took a look at ebay and see that one can buy a Garmin 800 for about $50. I'm still using one I bought in '12. You'd also need the companion speed and cadence sensor and a Garmin heart rate strap and transmitter. It's way, way worth the money to have real time numbers in front of you which tell you what you're doing. When I ride by heart rate, I watch my heart rate and cadence, nothing else really. I might glance at time, distance, speed, or gradient, but just a glance. I ride by HR and cadence and try not to notice speed, because it's irrelevant. It doesn't matter how fast you are, it only matters if you're working at the effort you want to be at for best results.
But moving on to your concerns. Yes, "the burn" is commonly said to be due to lactate build-up in the muscles, though lactate has actually nothing to do with it. It's a limiter for effort, whatever it is (it's actually hydrogen ions), because your muscles eventually choke on the lowered pH:
https://pubmed.ncbi.nlm.nih.gov/30382520/
To address this issue, the most favored method is to do over-under intervals. You make them burn, then back off until they don't, bring the effort back up again, etc.
https://www.trainerroad.com/blog/ove...s-for-success/
https://www.strava.com/training-plan...ining-glossary
Leg hurt more with 170mm? Probably an issue with stretching and being undertrained. Stretch every morning, these stretches:
https://www.bikeforums.net/road-cycl...l#post15372967
To train the legs up a bit, the best thing I've found is full depth (ass to grass) barbell squats, 3 sets of 12, enough weight on the last set that you can't do 12. Fix you right up - well, make you really sore until you get used to it. Twice a week. Start off with no weight at all. See youtube. I did my sets yesterday.
In any case, accurate instruments will have you sorting it all out in no time. For cadence, get used to doing 90 on the flat and 80 climbing.