When you have done several active days and reached that point where’s not much left. Do you use it all up and push to failure or drop the intensity and finish. I’ve always done the latter, including today but during the long 15minute intervals I started to think about it and what is best for training 
After an hour+ the session still hasn’t uploaded so this is a snapshot
I’d speculate at two possible answers: Either, Or.
If you want to improve endurance go long even if its at reduced power. If you want to go hard go hard even if it’s reduced duration. So train to your goal.
Also if you do drop power try to keep in the same power zone so maybe bottom of VO2 rather than the upper end of VO2.
For my two 'pennorth.
I’d say it depends on where you are in the training block.
Is this week #1? Then I would not push too hard. Maybe even get off the bike altogether and start recovering for the next week. A good month is more important than a good day.
Is this week #3 right before a recovery week? In that case I would push all the way to failure before pulling the pin.
Doing 45 minutes of endurance out of the blue really isn’t going to do too much for you. Sure, it’s good to get a little more TSS, burn some more calories and get saddle time. But it’s really the least important part of training if you are doing a lot of threshold work.
It’s the end of week two but the calendar seems to have jumped to week 3 when I added the club TTs in which suddenly restarted. It’s a rest day tomorrow but it looks like week 6 (or is it 5 
) until I get a proper recovery week.
You are always better off finishing the session by decreasing the intensity or adding backspins than going all out, blowing up and finishing half way through…doesn’t depend on what you are training for or where you are in the schedule. That said …if it happens more than once something else is wrong that needs investigating 
Itll happen once every 1 or two months with me. I’ll ace sessions for a bit and go for one session too many when I am bored
In this case it’s very possible that the best for training would be to call it quits after interval 3 and get some rest and hit the next session when you’re ready to hit it.
But if you want to complete a session, then reduce the intensity.
If you’re failing sweetspot intervals, you’re either fatigued, or your FTP is too high and you’re doing threshold rather than sweetspot.
Bored and fatigued as a result
I think if this is only happening once every month or two, you are doing really great and don’t actually have any problems.
We all have bad rides. Keep up the good work!
a slight deviation of topic; what if taking 1-2mins between intervals not pedalling and catching breath etc means that you’ll finish the session… is this a good habit to be in?
TR people will probably not like this but I don’t think riding to failure should be done very often except for testing and in races. If you’re constantly pushing yourself hard enough that you have to give up short on an interval, even if that is once per month or every 2-3 weeks I think that is too much.
I just saw a post on another forum about someone who was using TR for 2 years and decided to try something new. He added a long ride per week in zone 2 (3 -4 hours) instead of the tempo or harder ride you would see on a saturday or sunday. Did more tempo work during the week based on HR and lactate vs % of FTP (this will mean you’re truly in tempo), one VO2 workout per week.
**They took their FTP from 270 to 320 and feel fresher day in day out than they ever did performing the TR plans.
I would say you will get more benefit from dropping the intensity period and riding in Zone 2 for an hour than banging your head against the wall killing yourself to hold on to the intervals in the plan.
Added to my original post
On almost every podcast and consistently on TR’s social media you will see them applauding pushing to your limits in training and going for new PR’s etc. Very often I hear “the workouts are designed to be hard but doable”, “use some back pedals or drop your FTP by a few watts until you can just… complete the workout”. I’m a nobody but I completely disagree with this sentiment. What those two quotes are saying is that you basically should push to failure or almost failure on every one of their interval sessions. Some will say that if your FTP is correct they shouldn’t be to failure. I’m referring to what people “hear”. I believe most people hear, “I should just barely be able to complete the workout”.
IMHO this is not a sustainable strategy, leads to mental and physical fatigue, more missed workouts, leaves some people dreading doing the workouts, and doesn’t train the appropriate systems enough. Endurance training is not like weight lifting or other power type sports. You should not be pushing to failure very often. It is about the right balance of training in different zones and then the amount of total volume you can do in the context of your personal life is what will determine how far you can progress. Being fresh to complete the Vo2 or anaerobic session will lead to higher quality work and improvement in those power zones. Performing them fatigued lead to lower quality, lower peak powers for anaerobic work, and high neuromuscular fatigue. Riding harder because you can’t ride longer doesn’t lead to long-term sustainable growth of your aerobic engine.
Yep - a failure every few weeks especially on tough sessions means you are pushing the envelope and are right on the edge - this is where you want to be - keeping going. It is when all sessions seem easy or you can’t finish anything that you have a problem that needs solving - well done 
