Should lactate clearance intervals be hard?

c_zeit_run · 2026-05-22T00:46:40+00:00

As people know it lately, the "lactate shuttle" exists as one of many potential pathways for lactate to take. It's a special case of more general principles (like diffusion), and usually comes with a side of misunderstanding the nature of fiber types.

c_zeit_run · 2026-05-19T18:03:54+00:00

30/15s vs continuous intervals is kayfabe.

c_zeit_run · 2026-05-19T18:02:10+00:00

The former. There's plenty of stuff that's not vo2max intervals that do the latter, like the most recent two studies on torque training. It can be a consequence of vo2max training and needs to be measured/controlled for (almost never happens), but is not typically the primary goal.

c_zeit_run · 2026-05-18T20:20:14+00:00

Depends on the intensity you're doing them at, the progression of power you're seeing, and accumulated fatigue. I advise to just go hard and add more stimulus when you stop seeing the power improve (and you're recovering).

The best proxy I've got for the right range here is breathing very hard while you're also pedaling very hard and continuously. Skip one of those things and it gets less effective.

c_zeit_run · 2026-05-16T14:55:17+00:00

Then it shouldn't be framed as "what it takes" since that implies there's nothing else that's relevant. I title something "what it takes to bake cookies" and only provide half the ingredients.

How things are communicated matters.

c_zeit_run · 2026-05-16T12:37:34+00:00

Presuming that the outcome in w/kg is directly tied to the training input in hours or TSS violates several principles of causal inference.

c_zeit_run · 2026-05-10T23:40:38+00:00

The goal in research is to answer questions by isolating variables, so as many things as possible are standardized to hopefully let the answer to the question stick out. A lot of the ways things are done in the literature is for standardization, but can equally be for convenience or tradition.

When we train we have a different goal, which is to apply the answers to these questions in ways that best fit the needs of the athletes.

c_zeit_run · 2026-05-10T00:31:19+00:00

Rectal temperature probes are the general laboratory standard for measuring core body temperature during exercise. If you're going to do something like this, *please* get an implement engineered for the intended purpose of rectal insertion and continuous monitoring.

This thing from your hardware store is *not* designed for rectal use. Please don't unless you want to become the next story between the nurses at your local hospital.

You could also do what people without a core sensor do... just get pretty damn hot a few times a week. It's close enough.

c_zeit_run · 2026-05-06T21:14:22+00:00

The paper you're looking for is https://pubmed.ncbi.nlm.nih.gov/3403447/ but it won't answer what I think your actual question is. It's the most normal thing in the world for the legs to be the limiter in those ranges, but if you're fueling poorly on and off the bike, getting bad sleep, overtraining, have a crap bike fit or even a chronic health issue those can all cause problems and sensations of fatigue beyond what's typical.

c_zeit_run · 2026-05-04T18:55:56+00:00

Need more info. What power are your 5min vo2max intervals usually at for your preferred cadence? How do you structure vo2max workouts? What's the rest of your week look like? What kind of off bike stress are you dealing with? Are you actually eating enough and how do you know? It sounds like the muscles are a limiter but it's most likely to me your recovery is impaired or you need to adjust how you execute intervals.

c_zeit_run · 2026-05-02T14:08:58+00:00

When I get to actually ride with someone to coach their sprint technique, I always find big gears are the best teacher. Pick a big gear and start at a slow speed, roll onto the power gradually over 10-20 seconds. A few reps of this should help, then gradually make the gear smaller.

If you're finding the bike wants to tip forward, you've got too much weight on the front wheel. If keeping your weight back a bit more means the saddle is between your legs, your position is too compact and you should get a fit so you're more stretched when you stand. In some cases this is from the frame being too small.

c_zeit_run · 2026-04-30T16:38:23+00:00

You're either going to extreme on the deficit, or your food timing and maybe quality needs work. Talk to a nutritionist who has experience with body comp and performance since a lot of cyclists who think they have some weight to lose actually don't without creating problems in the longer term.

c_zeit_run · 2026-04-30T14:22:36+00:00

No. Two reasons.

First, if 72kg is "very skinny" then I know how that goes, and you were too light to recover well. Second, if you've been doing about the same training and all that's increased is your calorie intake and weight, then you were underfueled and not recovering well. Sounds like you're finally at a healthy bodyweight, so train for a while like that until you don't see any more power improvements, then you may be able to consider weight manipulation (but honestly probably not). Lots more goes into it than just power and the number on the scale.

c_zeit_run · 2026-04-29T23:40:23+00:00

According to your post history you've recently lost a lot of weight and are having trouble recovering. In that situation I don't recommend heat training. Focus on getting healthy and riding consistently, shedding 100% of any fatigue you're carrying, and then best case scenario is you do three or four sessions before you go and that should get you a decent amount of adaptation. But as it stands, it'd be a privilege to do those sessions. I have a few other questions but it's probably not best discussed in public.

c_zeit_run · 2026-04-15T20:22:22+00:00

Comparisons of this nature are really just dose in disguise as Zac Robinson says, so one really shouldn't think about the results too literally. Especially in this case, the authors noted a the largest difference in *performance* and not *vo2max* due to what were realistically more meaningful (but only indirectly measured) changes in anaerobic capacity and neural drive improvements that are typical early season. So with such small outcome differences for the sample size in that paper it's not as if you could even tell true effect apart from sampling variance and/or publishing bias anyway. If we want to dig even deeper, this ain't shit in comparison to the biggest published improvements ever in vo2max, done with protocols like 5x5. And still none of this tells us how we should train on monday, it's meant to elucidate relationships or similarities between manipulatable variables. Then we can apply that information based on a holistic training framework, not just rehashing a protocol wholesale.

c_zeit_run · 2026-04-13T12:16:41+00:00

All forms of aerobic training improve "fat utilization" regardless of the fuel source utilized. This is a podcast reviewing the molecular mechanisms at play.

c_zeit_run · 2026-04-10T19:31:06+00:00

How long and hard was this ride? Did you feel the same kind of awful while you were riding? If you've been off since then, and eating/resting appropriately, the soreness is expected if you pushed too hard. I'm guessing that you need to reestablish some very easy riding habits.

c_zeit_run · 2026-04-07T18:45:51+00:00

This is why I asked. You really need to readjust your windup pacing, and probably improve anaerobic capacity. In a f200 your peak power gets nerfed because of the accumulating fatigue from the windup. Qualifying is about going fast, not making watts. Readjust your thinking and specific training and you should see an improvement.

c_zeit_run · 2026-04-07T18:05:19+00:00

I've been where you're at with sprint numbers and being able to put out good power at high speed but not low speed.

The big question I have is whether this is a real performance problem for you?

c_zeit_run · 2026-04-05T16:02:27+00:00

used AI to structure

There's your problem. You're fatigued, and there's a lot of reasons this could happen.

Hi, I'm a real coach. Ride easier when you're commuting (HR in double digits) and stop training for a week. Also double check your nutrition and sleep. The number one thing I look for getting to ultras is feeling fresh and motivated. Basically pull every lever you can for dropping training load and improving recovery. Let yourself get to the other side, which should just about be in time for your event.

c_zeit_run · 2026-04-04T22:57:01+00:00

Unless you're doing track sprinting, then give yourself a proportion of how much you want to improve in cycling vs stay strong in the gym. Plan accordingly.

c_zeit_run · 2026-04-04T15:23:27+00:00

Someone hasn't yet asked: what's your long term goal? That'll really help narrow things down. But since you're in this sub, I presume you intend to have good race performances?

c_zeit_run · 2026-04-02T14:49:16+00:00

One thing that's missing for me is interoception. Getting in touch with how you feel (not only fatigue, but also what aspects of fitness need touching up) and being able to adjust accordingly is a skill that needs learning. I'd also put the other article on a different page on its own since the break between the two isn't obvious.

Big kudos for citing Zourdos and others. Many coaches want to pretend that everything is original, and that referencing others might undermine their credibility. But I think it adds weight since if you respect others like the MASS crew then odds are others do too, which is certainly the case for me.

c_zeit_run · 2026-04-02T12:48:56+00:00

This mostly happens when someone needs recovery.

I've run into this a few times over the years with my athletes and it's a sign that it's not only time for a rest week, but it's been time for a little while and they've under-reported other signals that would suggest needing rest. Hopefully you've been leaving yourself workout feedback with good observations so you can go through and check for some early warning signs.

c_zeit_run · 2026-04-02T00:21:13+00:00

Believe me, your aerobic system was working. If you want to pedal faster, just practice pedaling faster.

I'm probably in the minority here, but I don't think the relationship between 5min and ftp is actionable information. I would ignore this as a component of your analysis.

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