Sweetspot intervals and heart rate

Am I right in thinking that correctly done sweet spot intervals should get one’s heart rate a good bit higher than Zone 2?

I’m asking as I did the Slide Mountain ride this morning. I struggled at little bit to maintain consistent power during the intervals (I’m doing all the rides outside and could have done a better job of picking my course) but looking at the three work intervals after the fact my power numbers for the laps are all in the range I was supposed to be in. But my heart rate never left Zone 2 for any of the intervals. This is making me think I may have my FTP too low (I’m very new to having a power meter and while I’ve done an FTP test I’m questioning whether I did it correctly).

  • It depends. Not all Sweet Spot workouts are created equal.
  1. Take note that this is a 2.0 Workout Level in Sweet Spot. This is rather low on the 1-10 scale of workout levels and should be considered an “entry level” workout regardless of the training zone in question. It is also a relatively low 0.77 IF (Intensity Factor) for a 1-hour workout which is not particularly demanding in most cases.

  2. Then look at the 3x10-minutes at 85% with 4-minute recoveries. The fact that 85% is used here relates to the 2.0 Level above since this isn’t even officially “Sweet Spot” per the TrainerRoad definition. They use 88-95% FTP as their official SS range so this one isn’t really in there. It is officially “Tempo” and again exists with the Sweet Spot labeling to serve as an entry workout with Sweet Spot progression as the goal.

  3. Depending on how much you missed the goal power, that could easily impact the results. Impossible to say more on that without seeing the workout in question.

  4. Overall, with the above info I would not necessarily expect to be hitting higher HR than Z2-Z3 levels but that is it’s own can of worms to a degree with inherent variability seen in HR.

  • This is a very worthwhile question but can’t be answered without more info about your test. Since you seem new to most of this, it is entirely likely your test could be less than accurate.

Thank you! Yes, very new to both training with power and structured training in general. My normalized power numbers for each interval ended up in the range they were supposed to be in for the workout. I think I need to re-do my FTP test.

@mcneese.chad as always makes some good points. I will also add that if you are doing your indoor and outdoor workouts with different power recording devices you may experience some substantial changes in power recorded which, in a sweetspot interval, could have you in a more zone 2ish power. In my case, I ride a quarq crank based power meter outside and use my tacx neo 2t inside. The 2 meters do not read equally.

Also, compliance with the intended zones (coasting etc) will have a big impact on heartrate.

Just my .02


Be very careful when using NP. It may be OK to use in this instance but it can be a less than useful number in shorter intervals.

  • 10m is probably good for duration in some cases, but it’s also possible that you have notable variability that alters NP enough to skew it from AP to be problematic in the sense of training objectives here.

  • I suggest a review of AP along with that and close look at the graph to see how well you really adhered to the targets.


In addition to everything @mcneese.chad said, if you are riding in the cold, you heart rate may be a couple of percent lower than what it would be indoors for the same output.

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As an indoor (isopower) workout, that would be on the level 2/3 border. Hardly worth breaking into intervals.

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20 min is the minimum duration over which I would even consider looking at NP. In fact, the original WKO+ software didn’t report it over durations shorter than that. But as is often the case, commercial interests overrode common sense/the advice of those with a better handle on things…


I couldn’t remember the precise gap but figured it was questionable in this case. Thanks for the clarity.

And for @bmarum’s benefit (in case you don’t already know), “The_Cog” happens to be the creator of NP and much of this area so you can take that to heart as the definitive answer.

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Yeah, I don’t expect this would be particularly demanding all else being equal, hence the points above. The fact that this was done outside raises more questions as mentioned and I don’t think we have enough info to know for sure, but per his basic question… seeing a lower HR is not a surprise to me with what we do know.

As far as breaking the intervals, that presumably relates to the lower Workout Level rating and whatever progression Adaptive Training has in mind per TR.


When I do intervals at this power, my heart rate barely budges unless I’m doing longer 3x20 or 4x20 at this power.

I wouldn’t worry about it. Since you are new to structured training, maybe test your FTP once a month until you get a good feel for it.


I really appreciate everyone’s responses and help. I struggled mightily to keep my 3 second power numbers in the range the ride called for. Sometimes I was 70 watts higher than I was supposed to be and sometimes I was 70-80 watts lower than I was supposed to be. I tried to correct that as quickly as possible, but I didn’t think about how that variability might impact my heart rate. I have a better course in mind for my next interval workout. Hopefully that will help with more consistent power numbers.

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I would wait and see how an actual threshold workout will feel, and wait until you step up some progression points before worrying about your FTP being too low. Sweet spot feels pretty damn easy to me, though I virtually never do them.


3 seconds is a bit too granular to pace a long interval outside. Personally, I have 3 and 10 second power on my head unit and when I do this type of interval, I hit the lap button and look at both the 10 second and the average power for the interval.

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Thank you – this makes a ton of sense to me.

Thank you. The software has stepped me up a bit already so I suppose I will let that continue to play out for a bit. I did one threshold workout last week and that one had my heart rate up into Zone 4 and subjectively felt a little challenging. So I suppose that suggests my FTP isn’t as far off as I think it might be (or that it isn’t off at all).

As you stated you’re new to training, I’d continue to let the software do its thing. It will also prompt periodically for FTP adjustments (either via AI FTP or scheduled tests).

It’s also quite difficult to really nail an interval workout outdoors, even with a power meter. Just too many variables in elevation/slope, traffic, etc. You really need a nice flat piece of pavement that’s relatively uninterrupted. It definitely takes some time to figure out the best places to ride. And that’s ignoring your own pacing - that’s a learned skill as well. The shorter the interval, the harder it is to nail the prescribed power, IME (more power = more speed = more chance of needing to coast or stop due to traffic conditions).


I do have a nice spot for most of my interval work – a 3 mile stretch with no lights, stop signs, etc. and that has a slight and almost entirely consistent incline. I’ll likely do most of them on that.

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To be honest many would not consider that sweet-spot, 85% is more mid-tempo to most.

@mcneese.chad makes very valid points.

Heart Rate can be very individual, decently trained your HR zone will be 0.5 - 1 below your power zone (this is a sweeping statement, but generally true.)



I have a 5-6 mile loop, but it has 3 traffic lights, 2 stop signs, and 4 right turns. It’s great because traffic is light enough to slow-roll the intersections most of the time, but I still have to slow enough to check for cross-traffic and occasionally wait for one of the red lights to cycle through.

There’s a rail-to-trail MUP nearby which has more consistent slope and intersections, but it’s way too busy with dog walkers and kids to be useful for faster workouts.

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