Right now I’m doing 3x intense days a week and 2x endurance days, I was wondering if there’s a general guideline on the length your intense workout should be to gain maximum benefits. I have mine set to 1.5 hours but if I can gain the same benefits from a shorter workout then I can add more Z2 time.
Any suggestions?
I don’t fully understand that question. Aren’t your intense workouts filled with z2 anyway? For example, even if you do something horrific like 5x5min vo2max, that’s only 25 minutes ‘intense’ work. If your workout is 1.5h in total, there is still nearly an hour of endurance work in there. (And some recovery).
How many hours a week are your training?
How many more hours a week do you want to add?
What weekly TSS have you been maintaining?
Using the example I think they are asking is it better to do that session in 60 minutes instead of 90 minutes and make an endurance ride on another day longer.
You could look at it the other way as well… do the 5x 5’ in 120 minutes.
I used to do this, but for myself I now find this far to much fatigue in a single season, so keep the intense sessions threshold and VO2max to 90 minutes or less.
Tempo I put into longer sessions… basically the longest I have the time and energy for.
As Ive made the VO2max sessions shorter… I add the ‘lost’ time to tempo, sweetspot and endurance sessions.
Based upon TR and other podcast experts that I have listened, I understand that it takes your body some (variable) amount of time to switch between sympathetic and parasympathetic systems. The net effect is that it is ineffective to think that you can switch between them.
There also seems to be a difference of opinion, whether segregating your intensity or zone 2 should happen near the beginning or near the end of your workout.
TR seems to lean towards putting your freshest/strongest self into your intervals. Inigo San Milan says the opposite. That is, to put your intervals at the end of your zone 2 ride. There may be a study on it by now(?).
I personally don’t think it matters. Whatever works best for your schedule and your recovery.
But it sounds like you have the time to add more time to your Z2 workouts. Why don’t you do that without shortening your intense days? More volume is nearly always better in endurance sports.
In my experience, I would struggle to do a good VO2 workout in an hour. It might be ‘good enough’ but if I had extra time to recover between intervals to ensure that each one was max then that would be better. Then for anything like FTP I wouldn’t be able to do a good threshold workout in an hour. You have say 20min of warm up and cool down then you’re only left with 40 minutes. That would only be enough for the shortest of FTP workouts and you’d have minimal to no rest. You wouldn’t be able to do an effect SS workout in an hour either.
I don’t know if there’s any scientific basis to it but Ive heard anything over an hour for VO2max stuff is counterproductive. Below you’ve triggered adaptations in that area but anything over an hour your suppressing them 
I guess my main concern with longer VO2/Sweet Spot rides is fatigue and discomfort, usually by the last block I’m struggling to maintain the power output, my sit bones hurt to the point where I have to stand up and coast, and now I have a yellow/red day. When I kept my interval days to an hour it wasn’t as bad, but I figured more volume would help. I wondered if there’s any benefit to a longer interval ride versus a shorter one. If you look at a 2 hour+ VO2 workout (Pilot for example) its mostly filled with Z2 anyway.
I start to get uncomfortable on the trainer after an hour, but I can ride all day outdoors with no issue.
I really don’t think this is true. Especially considering volume is a pretty big driver of VO2 improvements.
This would be a decent reason not to stretch those workouts out.
I think this depends on the structure of the actual workout. All things being equal, a longer one will be better because you’re riding more. But if you can’t sustain the output of the intervals when spread out over a longer workout then I’d keep them shorter or put the intervals at the beginning of the workout and then do the extra endurance riding at the end.
Yeah, that’s super common and another decent reason to keep those rides shorter.
Maybe is, maybe isn’t, but I built my VO2max (albeit garmin) when I was younger to 75 so it worked for me when my old coach told me the line
If you are doing VO2 max workouts (5x5, 6x3, 4x4 etc) especially stacking them back to back or even double days it very much is true. In those cases you want to maximize the stimulus you can get and still recover, adding volume to those sessions themselves is counterproductive.
I recently switched to doing 2 1.5hr interval workouts instead of the 3 1hr workouts.
All it seems to do is pad the workout out with more endurance work.
3 1hr interval workouts a week work but I was on my limit with a long ride at the weekend as well.
I was doing 1hr Vo2 Mon. 1hr Endurance Tues. 1hr Sweetspot Wed. Rest Thurs. 1hr Threshold Fri. 3/4hrs Endurance Sat. Rest Sun.
Currently doing 1.5hr Sweetspot Mon. 30min Recovery Tues. 1hr Endurance Wed. Rest Thurs. 1.5hr Threshold Fri. 3/4hrs Endurance Sat. Rest Sun.. The 1.5hr Sweetspot will change to Vo2 as I come out of base.
I find I’m better recovered and can hit all my numbers on the interval workouts which means in effect I’m marking them as easier instead of being fatigued and marking them as hard.
I find the longer warm up helps as well instead of cramming the intervals into a 1hr workout.
How many hours a week are you doing and how many could you (or want to) do?
The “sit bone” thing has me perplexed. Sounds like more of a fit issue than the interval intensity. Typically my sit bones hurt much more on easy rides. During intensity, there’s so much less pressure on the saddle.
I’d go 3 days of 1 hour intervals and add 90 min to your endurance rides. Or….i guess I’d let plan builder decide because I’m a believer. But in 60 min you get 20-30 of intensity and 3x per week is good for young strong guys. If you’re a geezer, 2 per week is good.
Joe (a geezer)
Really depends on what type of “intense” you’re targeting. Sprint? VO2Max? Threshold? All of these have different recs. Furthermore you want to be thinking more about “time in zone” than length of the total work out. For example, 20mins cumulative time in Z5+ for VO2Max work is good… wouldn’t want more than 30. And the amount of rest in between intervals is more a question of how much recovery you need to make the next interval another quality interval. For threshold time-in-zone could be 30-60mins.
This is a good question!
I think, in this case, personal preference can come into play.
If those long 90-minute workouts are a pain in the ass, then maybe dial them back to 60 or 75 minutes and ride a little longer on endurance days.
If you’d enjoy yourself more with that schedule, I don’t see any real reasons not to switch.
If, however, you could at some point start doing those 90-minute hard workouts outside and get through them without discomfort, they are highly productive!
At the end of the day, we’re all choosing to train, though, so make sure you’re enjoying yourself and not suffering more than what’s necessary. 
Sure, but I was talking both in context of OP who is doing only 3 intense days a week and the other response who said:
Which is just not true.
As is always the case with adding volume or intensity. If it affects your ability to do the work that will drive most of your adaptations at that time then it should be reconsidered. That can be both doing too much volume during a VO2 block so you’re too tired to go hard enough and if you ride too hard all the time and you can’t do more than 10 hours a week without burning out. In one you should do less so you can go harder and in the other you should go easier so you can do more.
A copy and paste from the responses just after:
But do what works for you!
I switched from 2x90 min interval sessions to 2x60 min since starting back training in September. I find I am less fatigued and can ride longer at the weekends and enjoy it more. It remains to be seen what it does for my fitness but early days …