Fatigue or Technical Problems?

I hope this is the correct topic to post this, I wanted to share these results and get some feedback on if this looks like fatigue or something off with my gadgets…

I decided to do 2 zwift races over the course of 2 days where I had planned to do workouts in my threshold range - one 30 minutes the other 45-60. I will do this to help with the boredom of trying to maintain an effort for this duration.

I had about 48 hours between the two with very light activity between. I felt rested, not completely “fresh”, but ready to do a workout. As, I started my warmup, my heart rate look good compared to effort but the power displaying seemed much lower. I thought I needed to just warm up some more. I did. Things still seemed off. I then got off to check tire pressure (I use a wheel-on Cyclops Mangus smart Trainer), check trainer tension, etc.

I have a pretty good feeling of where my effort is and where my HR should be with that effort. Once the workout/race started, I went out hard. My HR went where it should go but the power looked to be low. As the race continued I tried to get to the numbers where I wanted to be, but the effort seemed way too intense and my HR was much higher than I wanted given the duration of the effort. I then dialed things back to where I felt I should be , still hard, but my HR to be around my threshold number. The power numbers where in the neighborhood where I would do an endurance ride with my HR in the 130-140 range but this ride is was in the LTHR range, where my effort felt.

Here are some comparison rides from Zwift power.

It does show that this effort looks to have a much lower power difficulty across all the duration but a very high HR compared to much easier effort ride with similar average powers - compare (3rd from top) “Festive 500 Group Workout” avg power is the same, but the NP and other duration much lower for the (top) “3R Volcano” ride but the HR much higher for both average and max. I would have expected, from the effort I was doing and HR, to be closer to (2nd from top) “3R Tick Tock” but with some decline in power since it was longer and carrying over some fatigue from a few days prior - not too mention being by myself and not zwift-drafting at all.

I would think if I really feeling dead in the legs and off on power numbers my HR could not be held at that high for the duration. Since I did feel pretty good and was able to hold an effort that had my HR around LTHR should I expect my power to be close? Or does this look to be an issue on the power numbers being reported from my trainer? I can supply more types of workouts and numbers if needed to compare.

Hey @bgkeen, thanks for posting and including all of the additional information.

So where was the 48 hours of rest between the two - was this leading up to the block or between the two race days? Or was this a 2 day block (1 race on each day)?

Was this a precipitous drop in power relative to HR - like, this happened all of a sudden? Or did you have any sessions similar to this in the past?

I’ve had this happen (and have seen it in other athletes) where you can’t produce the power, but the HR is high for the effort. I don’t have a great answer at the moment other than it could be your body telling you something. You might take a couple days lighter and then try to replicate the efforts. When it happens to me it usually means I’m getting a cold or something, or still getting over a cold. Or just low fitness if there was a lot of time off the bike.

I’ll say that on today’s Zwift meetup you looked like you were riding well for the type of ride we were doing, and although I only checked on your HR numbers 2x throughout the ride, it seemed at a reasonable level relative to your max HR at least in those few times I checked.

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Thanks for taking the time to read and respond.

  • I had about 48 hours of rest between sessions.
  • I cannot recall another session like this where I felt fairly good/strong and was able to push my HR to the limit as I did and maintain through a full session (and feel pretty good the following day (yesterday during the zwift meetup). I have had days where days where I had to push hard to get power where my HR was high relative to the effort but I don’t think I was able to push as hard or as long to get my HR as high as I did. In those sessions I either pulled the plug or really dialed it back to get my HR below 130.

Regarding the zwift meetup ride. I was really interested to see how things looked for a few reasons - did the numbers seem to where they felt and how did I feel after the effort the day before and the fact that I donated blood about 3 hours post the “troubled” session (about 27 hours before the meetup).

I felt things seemed to be a little more in tune to how I felt, maybe HR a little higher but that can be due a little fatigue from the day before and blood donation. I did mess around with my tire pressure and made sure trainer was torqued appropriately.

But, I think I may found a culprit as I was getting things ready. I did check the tire pressure the day of the race session. When I checked before the meetup I noticed that the valve was not tightened and the tire was at 40psi…So, I am going to put this under the category of “Operator Screw Up” since I clearly forgot to tighten took needed pressure away and everything today seemed to fit. D’OH! :man_facepalming:

I was about to add a couple thoughts, but saw your most recent post and it looks like you found the issue. Heart rate being high when your power is low can definitely be a sign of fatigue, but you’d feel it as well. If you’re feeling good, had some rest, but the power on the trainer/Zwift seems low, it’s likely a mechanical issue.

But I did still want to add a comment that Ryan’s right - a high heart rate relative to power can be a sign of short term fatigue. When you’ve done some hard training, you’ll have some muscle fiber damage, so you’ll need to recruit more fibers to produce the same wattage. Recruiting more fibers increases the stimulus on heart rate. Fortunately this type of fatigue only takes a couple days to recover from. The trick is to recognize it and pull the plug on anything intense. Your legs aren’t ready when you see that.

Thanks for the feedback and thoughts. There is a possibility there was some fatigue that I was not feeling but my body did need to make adjustments. I did a pretty hard session yesterday…I guess the next thing to do is wait 48 hours and try a similar effort to last week and see what happens to confirm…We are sick creatures :slight_smile:


I did another round of a harder workout in the form of a race followed by another similar session 48 hours later. I’m pretty confident it was the mechanical/user problem and not fatigue.

This round I did a much longer race (90 minutes - GNFS E-Fondo Florida on RGT ) than the Sunday before and then 48 hours later I did a 30 minute Zwift TT followed up by going right into 3 sets of 2x2s (2 minutes somewhere between 20 min and 5 min max with 2 min recovery and 2 min between sets). So, I would have not been too surprised if my numbers were a good deal lower Tuesday than they were Sunday…maybe not as low as the prior Tuesday.

But I think this round showed I probably was not fatigue that caused the power drop and that I can recover from a good threshold effort (especially a 25 minute one) in 48 hours.

The table below highlights the 2 workouts done 48 hours after another one shows my 2nd workout is as strong as the 1st and this week’s round the 2nd workout showed much higher power than the first with very similar heart rate. This also seems consistent with how I felt each week on the second workout:

One thing to note, as went from the TT to 2x2s, I got stronger in the 2x2s as the sets went on with fairly short recovery periods. Which I think indicates had adequate recovery from 2 days prior.

So, I am going to put this one to bed for me. Especially since I felt slightly fresher last week than I did this week. But thanks again for the feedback and info. It is good to know all the possibilities that it can be.

BTW, if you have not tried RGT for a race give it a try. It was a pretty neat platform and the whole drafting part is much better than zwift. It also shows data on how many watts you are saving while being in the draft. Which is good until you are sitting 3rd wheel, on your limit, and it says you are “Saving 800 Watts”!! I am hoping to do most of the Sunday E-Fondo races until the Series Championships, since I think I qualified.

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Hi @bgkeen,
Glad you got it figured out and doesn’t surprise me! Mechanical issues were the more likely explanation. Only comment I have is I wouldn’t make a generalization about being able to recover in 48 hours. Our bodies aren’t that systematic. Sometimes you’re ready to go in 24 hours, sometimes it can take more than 48 hours. There’s a lot of factors and its impossible to track all of them. That’s why its so important to gauge yourself every day and make on the ride decisions.

For example, two Sundays ago, I did a long six hour ride and felt great for my intervals on Tuesday. This Sunday I did a very similar six hour ride and I was useless on Tuesday. It’s now Wednesday and I’m still not feeling 100% yet. It really does vary.


I hear you…I did feel a hesitant of how I wanted to word my degree of confidence and assumptions of robotic stress recovery cycle. As you allude to, it is hard to know the state of things even when my feeling seems right but there may be something hanging on from some accumulated stress prior. I just know now to check my tires and valve - until I spring for the direct-drive trainer :slight_smile:
Thanks again for taking the time to look and for the insight.

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@bgkeen, Glad we could help!

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