First Zwift road race, can't sit or bend at the knees. What's going on physiologically?

So I did my first Zwift road race and pushed hard (for me), average was 265 watts for 1hr 25 minutes, IF was 1.04. Still got destroyed in the “C” category but oh well, still money in the bank.

The issue now is that my quads, specifically the vastus medialis, are so sore that I can’t sit or bed at my knees without a lot of soreness. Now I cramp hard and I cramp a lot but I’ve never had this kind of weird soreness right after a ride. I might have something similar the following day, like DOMs, but this is more painful and onset was about 3 minutes after I got off the trainer.

Does anyone know why this happens physiologically? Would be interested to know how to prevent it from happening again. It’s not a cramp, that’s fore sure, but it’s certainly painful.


This likely boils down to a combo of nutrition (before and during?) as well as a relative effort here vs recent training.

  • Did you come in with appropriate fueling, hydration and such, as well as fuel during?

    • If you didn’t have proper food and drink, a hard effort can lead to this.
  • How does this rate compared to recent efforts in the last couple of weeks.

    • If you hit this much harder via intensity, duration or a mix… than your recent workouts, being smoked like this might be expected.

To a degree, it is all “preparation” related in how you loaded and trained prior to this effort.

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That sounds like what my legs would feel like if I had 1.04IF for 1.5hrs. I usually feel smashed for at least a day if I am .9IF for 1.5hrs during zwift races.

TIme to up that FTP?


Yeah, I almost mentioned the IF vs time vs FTP. Seems likely to indicate there is room for change, but that may depend on the actual power profile a bit among other factors. In any event, that’s peripheral to the physiological issue that seems to be the focus here.

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Sounds like you just went too deep. Zwift racing does that. You don’t need to worry about race lines, keeping the bike upright or anything else other than putting down the power. As a result, you can end up pushing beyond what you would do outdoors or in an indoor workout. I can hold power in a Zwift race well beyond what I can do in a crit or road race, but unusually keep the full gas efforts to under an hour.


Thanks for the replies!

Good point. I had a hectic day yesterday and had less carbs than usual, I guess this could contribute to rapid glycogen depletion in my quads with a harder than normal effort. I took in about 120 g of carbs while in the race.

I skew anaerobic. I spent 34% of my time in tempo and 26% of my time in VO2max or above, only 21% of my time was at threshold. When I look at the power profiles of the other cyclists I finished with, it was more 50% at tempo, 20% at FTP, and less than 10% at VO2max and above.

That said, my threshold is pretty low compared to what I can do anaerobically :frowning:


I’m guessing your threshold (FTP) is actually lower than what you have it set at. People that have much more anaerobic power than aerobic tend to test too high, especially on the ramp test or 8 minute test.

Wait a week and try the 20 minute FTP test. I bet you can’t hold your FTP, even though you’re supposed to be able to hold 105% (because you are supposed to last for 40-70 minutes at FTP).

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You are preaching to the choir my friend, and no disrespect intended it’s just that I wholly agree with you :smile:

Ramp test overestimates my FTP by at least 5%, AI FTP had me overestimated by 10%; even the 20 minute test overestimated my FTP a bit. For my owner purposes I do an hour test to set my FTP, it’s currently set at 275 watts which might actually be a bit low now. I’m not saying that FTP is your hour power, I just choose to do an hour because I know my body and I know what threshold feels like for me, an hour long test allows me to “feel into” my threshold power and make adjustments as needed.


A couple of observations…

In any race, including on Zwift, there is a tendency to push hard and often beyond what you thought were capable. This will take a toll on your body and you will need time to recover.

You need to learn to “play Zwift”. Racing isn’t just a time trial. Those that were spending time at tempo were probably more efficient at drafting and knowing when to burn their matches.

It’s really easy to under-estimate the amount of fluid you need to take on during a Zwift race. Especially if your fan game isn’t on point!


Thanks for the advice.

Yes I did notice how easy it was to push harder than I wanted. On the road, probably 40% of my energy is focused on safety so I have to mitigate my efforts to make sure I don’t crash. There’s none of that on Zwift which allows me to just go HARD.

I was actually drafting most of the time at tempo. However I did notice that there was a lot less coasting than in real life road races.

I also noticed that it’s much harder to drop someone on descents in Zwift than it is in real life. Thanks to my 97kg weight I’m usually able to get a good minute gap if I go hard on the descents in my local group rides/races. On Zwift, similar length rollers/descents will net me a 2 second gap at best. Funnily enough, going up hill sucks as much as real life :stuck_out_tongue: .

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1.5 hours at 265 would crush me…chapeau


Thanks but I’m also 97kg, so unfortunately not a w/kg monster :stuck_out_tongue:

I would examine your electrolyte intake also. I’m wondering if you need to up your salt prior and during your race.

I skew very anaerobic and ran into the same type of trouble last year on very hard group rides. My legs hurt almost immediately after the rides each week. Overnight, I’d have horrible pain or cramping or both. Halfway through the season I started upping my electrolyte intake before and during the rides and then I supplemented with Mg once per day. What a difference that made.

So in the end, I don’t have a good way to describe the physiological reasons for your pain other than a possible temporary mineral depletion or imbalance.

There’s a good few things in your post that you can do differently that will save you energy. I don’t think the answers lie in fuelling etc, but learning how racing on Zwift actually works.

You’re never going to drop anyone on a descent in Zwift and only one circumstance that you should ever be coasting😉