Burning doing Z2 after a hard workout - what is happening?

I did a fairly hard interval workout this morning (~20 min total time in zone above FTP…plenty of rest between intervals). It wasn’t anything out of the ordinary but I went rather hard. Day off yesterday and ate a ton yesterday and this morning…fueled the ride decently.

After my intervals I rode light for 5 min then wanted to do some high Zone 2. As I pedaled along I felt some pretty intense burning in my legs (mostly hamstrings and gluts). I was able to put out the power just fine but it just burned pretty bad.

A) Just wondering what was going on? I guess I wasn’t clearing the lactate? My breathing was a little higher than normal at that power but not quite as much as a threshold ride.

B) if that happens again should I just keep going? Is that some kinda stimulus I’ll break through and be stronger after? I kept going for 45 min because I was kinda just curious…I only stopped because I had to go to work. I felt like I could have gone another 2 hours like that. (Feel totally fine now a few hours later.) or am I just flooding myself needlessly?

Just more curious than anything. I’ve gotten burning before but it just went away really fast.

You were still tired from the intervals.

I’ve found it can take the legs a while to recover from hard intervals but they may feel better as the ride goes on. 20 min above FTP is hard going, so I don’t see the need for hight Z2 straight after, just ride easy for a bit.

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That’s the fatigue in your legs which hasn’t been cleared yet. It is totally expected.

Yes — if you can recover from the efforts.

From personal experience (N = 1) I can recover better following your strategy (tacking on some endurance work after a workout) than adding another endurance workout of equivalent length to my schedule.

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From lactate handling angle, here’s what happens during Z4+ → Z2 workout:

  • Z4+ → High lactate production, accumulating due to glycolytic demand
  • Early Z2 → Maximum lactate oxidation; rapid clearance (10-15min)
  • Late Z2 → Return to steady state; finish clearing all residual lactate
  • Overall → Training both sides of the lactate shuttle: production → transport → utilization

Intensity that maximizes lactate oxidation varies. Something like ~70-80% of FTP for fit athletes.

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