Not all TSS is equal, low vs high intensity

Hi friends, i have created myself a custom workout in TR to accumulate low and easy miles that i use on rest day between my hard sessions. (I wont go into the polarized vs sweetspot debate, but i feel i need some more easy days that TR prescribes to deal with the hard days).

I have a 2 hour workout at around 60-65% of FTP, but in it i have 7x30 second sprints, first 4 at 200% and then 3 at 300% of ftp. The sprints are 15 minute apart spread out. I added these sprints to increase the level of my hard efforts in races, and i also have a strong belief in that triggering these systems will also benefit my ftp development, leading to increased recruitment of different muscle fibers and energy systems.

Sometimes i skip the sprint intervalls, if im having a tough day, or if im doing something on the computer while cycling (playing a game etc). After the workout, i have to say i dont really feel much fatigue from the sprints when i do them, and recovery the next day seems similar.

However, doing the workout without sprints yields me approximately 70 TSS, while the workout with all sprints gives me something like 130 TSS (just as much as a very hard O2 og SSP session).

Should i not emphasis this much? Have i found a life hack to accumulate more TSS, or is it just that the TSS scale does not rly fit my rider profile (being somewhat of a sprinter). Am i fooling myself by ruining and “easy day”? Any advice or suggestions?

My understanding is that TSS is supposed to be predictive of glycogen use. The only way to really answer your question would therefore to be to repeatedly stick a big needle in your leg.

Based on this study, though, that first 30 second sprint would use up about 20% of your muscle glycogen stores, but with possibly much diminished use thereafter. That’s about as much as you would use during an hour of moderate exercise. So, maybe the difference in TSS isn’t so far off after all?

Regulation of skeletal muscle glycogen phosphorylase and PDH during maximal intermittent exercise - PubMed

Interesting :face_with_monocle:. I’ve always thought those sprints in workouts like Pettit +1 were pointless and more of way to keep the workouts more engaging. Maybe there’s actually some benefit to it.

To me that doesn’t loo like a recovery ride, it looks like a anaerobic capacity workout. Those tend to look like short, hard intervals with tons of recovery in between.

My rules (for myself) for an active recovery day are: 60min or less, all zone 1. I am not a fan of the term ‘junk miles’ but the only thing I really throw into that category would be zone 1 for more than 60 min. Too hard to be active recovery, too easy to drive adaption.


I agreed with you Craig. I am z1 and sometimes will even turn pettit down. I go really hard on hard days and really easy on easy days.


I have done Lazy Mountain -2 and Lazy Mountain more times than I care to recall. And Pettit -1 for a ‘light endurance’ ride during recovery weeks.

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30 second intervals at 300% FTP sounds wrong. I’m not exactly a sprinter but I’m not a slouch either, have won and had high placings from bunch sprints in crits. Just checked and my all time 30 second PR is considerably less than 300% FTP so I couldn’t even get through one of those intervals. Do wonder whether your trainer/PM is scaling properly (think quite a few don’t work all that well with sprint power even if they’re pretty reliable below ~500W). If you are actually capable of doing 300% FTP for 30 seconds then it certainly doesn’t sound like any kind of recovery workout!

I do sprint workouts similar to this with a handful of 30 second maximal efforts interspersed by enough easy riding to fully recover. I do them outside and go by RPE not target watts, I do them on days when I’m fresh, they rarely last more than an hour unless I bolt on an easy coffee ride afterwards, and the goal is absolutely on improving my sprint (technique and muscle recruitment as much as anything else) and not on recovery. And yes, I think TSS for this kind of workout is largely meaningless.


I guess we all have different strengths. My 30 second power is 290% of FTP. I could do a set at 200% pretty easily. A set at 300% would probably do me in well before the 7th interval.

It is pretty stiff. Only about 1 out of 10 people could do it, and that’s only once.

But, based on the graph it appears that @callemacody uses it as more of a target, and the sprints themselves are actually “fly and die”.

@callemacody I think you have the right idea, perhaps slightly wrong execution.

It’s very common to sprinkle short sprints into an otherwise basic endurance ride, which is what this is (agree w/ comment that this isn’t recovery, and that’s fine…not supposed to be). It’s a bread and butter endurance ride.

When I was a competitive runner, we used to always throw in strides of 10-20sec on base miles. Very standard stuff.

Since these are sprints (and others on the thread can debate any science that might be associated with this, my comments are from personal experience and the experience of the half dozen coaches that have given them to me over the years):

  1. make them shorter. 10-15secs
  2. yes, skip them if you’re not feeling it, but don’t make it a habit
  3. don’t base things that are too far above FTP off of FTP. All out is all out. I don’t ever think: “today I think I’ll sprint at 200% FTP and tomorrow some other percentage.” Doesn’t matter what % of FTP something is when it’s that high. Just drill it, recover, go back to zone 2.
  4. although they may serve to break up the boredom, that’s not their primary purpose

Often what I do is don’t actually add the sprints to the workout ahead of time (solves your planned TSS problem). And, no. Nothing to do with your phenotype or physiology profile.

During the ride, when the spirit moves you, bam! go gogogo gogogo…ok, cool. As long as you’re fully recovered from the previous one, don’t get hung up on where they are in the workout.

My coach often gives me 4x10-15sec, but doesn’t complain if I do 5-6. If I go too many workouts without doing any, he’s like: “sprints, bro. it’s a thing…do them”.

If your intention was to turn these into some sort of interval session for anaerobic capacity (maybe that’s why you chose 30secs), then I would not execute them this way.

If that’s the intention I think you are better off with some of the more standard high intensity interval workouts. Just not too many of them, as you’ve probably picked up from all the arguing over intensity around here.


I agree with this.

@callemacody. Are you using them as a target or do you mean to actually sprint? If you mean to actually sprint, it’s “fly and die” as @old_but_not_dead_yet says. Who cares what it is relative to FTP. You shouldn’t be doing so many of them (and for so long) that it affects TSS that much anyway.

So I guess I can’t tell whether @callemacody is trying to do “endurance + sprints” or “improve FRC”, those are two different workouts to me.

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Thanks for good feedback. One correction, its first 4 at 200% and last 3 at 250%, with my current FTP that means approx 700 watts. Most times im not able to complete the whole 30 sec effort, but some times, i am :blush:

I agree that this is not a full recovery session, but i am doing this somewhat of a base phase, trying to accumulate more time exercising, and this kind of workout would then fit well between a hard session and the stright recovery sessions that i usually place before my hard days (an hour easy jog).

As the “sprints” are 30 sec efforts, its not strictly an all out sprint, more like very hard efforts to close gaps, sprint out of turns chasing a wheel etc.

To sum up, this workout is like “base miles” for me, and apart from the intervalls it feels to easy that i do believe its not in the “junk mile” category, i feel its more base training, with some added sprints. Best of both worlds :D? I was just surprised at that high TSS i was earning, because for me to accumulate this kind of TSS around sweetspot would feel very much harder than the 10ish TSS i am earning per sprint here. Simply put, the TSS scale seems too exponential for my power curve, earning me the same TSS for 30 sec sprint at 250% as i would for 10 min on threshold 100%.