The OP said he’s doing LV plans plus 2-3 days of Z2. That is a solid approach to using TR correctly - LV intensity sessions + endurance riding. I think that’s about as good as you can get on about 6 hours per week.
Once the weather warms up, he’ll be even better if he can do some 3+ hour endurance rides on Saturday or Sunday.
I believe the Z2 work is cumulative. Think of it this way - if you do 2x75min Z2 all year that is 75 hours per year of training. That is a huge amount of aerobic fitness training for someone on an LV plan.
It also depends on what people are training for. For example if you are training for a century or big fondo you can do a progression where you start with a 2 hour endurance ride, then a 2.5 hour, then a 3 hour, then a 4 hour, and then a 5 hour.
After a 5 week progression like that and a rest week, you’ll be ready to rock your event.
That, I think is my take, 75m is enough but a minimum (more is much better.) IMO for 75m you need a bit of Z3 in there, assuming for the individual Low end Z3 is under LT1.
Having said that on a TR LV plan every little extra helps, any extra Z2 over an hour is going to help but obviously not as much as 90m to 5hr. It depends what your general background is, and where you are on your progression as an athlete.
If prior to doing 75min Z2 rides on endurance days, you were doing 60min Z2 rides (for example), then yes, that is enough to improve. If prior to doing 75min Z2 rides you were doing 90min Z2 rides, then you’re likely just doing enough time to maintain.
Once you have adapted to doing the 75min Z2 rides, you will have to progress it (more Z2 time, maybe introduce tempo, etc.) to improve.
As others have pointed out, 75min Z2 is well worth your time.
The question will be whether a 75 min Z2 ride is challenging for you. For Z2 is normally the duration that challenges the muscles. Z2 for one hour might be easy, easy for two hours, easy for three hours, moderate after four hours, hard after five hours.
You’ll want to progress the duration which will progress your endurance. You should feel fatigued after your Z2 ride.
My take on it as well. If by doing it you are going some way to maintain your aerobic fitness then by definition you are not losing it which in its way is a gain.
I really want to see a study on this exact issue. Why is 3 hours the magic number, and is 3 hours in one to better than 5 hours cumulative over the week in 5x1hr sessions etc.
Also what about if I’m doing an interval set which lasts 2 hours. If I add one hour extra at Z1 do I get this magic 3 hour adaptation or not because it wasn’t all steady at Z1?
If 3 hours is the magic number then how many of these should you be doing a week to be a beast.
You hear it a lot about splitting up the Z1 long weekend ride if you can’t make time for one go. Is that really the same, sounds like a good one for the TR podcast though maybe it’s been covered.
In a polarized plan, ANY work above Z1 means it wasn’t a Z1 ride. The idea is, for example, to do one REALLY hard ride, and then all the other rides for the week purely in Z1.
I went back and listened to the Peter Attia podcast with ISM. Zone 2 is maximal stimulation of Type 1 muscle fibers, aka Fatmax, or LT1. Yes, you are correct. I’ve been doing my zone 2 rides below that and seen a significant increase in power for the same pulse.
5x1 hour isn’t the same as 5 hours as it is fatiguing the fibres that count…in the UK most of those in the know on the TT forum who know what they are talking about say that 4 hours is the “magic time” past which you start to get big benefits. That said, if you have only been doing 2 hours zone 2 then clearly 3 hours will become the magic time. However, I did loads of zone 2 in lockdown last year and found that knocking out 3 hour rides was easy, but no matter how many I did - about 50 odd last summer - when you got to about 4 hours it started feeling different and required more focus…anecdotal of course…
