So what good are those long zone 2 training sessions doing?

This new review article claims that zone 2 is less effective than higher intensity training:

"We conclude that current evidence does not support Zone 2 training as the optimal intensity for improving mitochondrial or fatty acid oxidative capacity. Further, evidence sug- gests prioritizing higher exercise intensities (> Zone 2) is critical to maximize cardiometabolic health benefts, particularly in the context of lower training volumes."

TL;DR

Zone 2 compared to higher intensity training:

• inferior mitochondria development
• no better at fat oxidation capacity
• inferior at improving cardiovascular function

Link to the complete document.

Getting the popcorn ready.

I'm thinking the key is volume. Z2 allows for more of it.

There is probably a crossover point where X amount of Z2 will cause greater adaptations than X amount of Z4. Z4 works faster, but how much can you do?

Even at my lower volume levels - 7-10 hours per week - If I do a hard Z4 session, say 3x15, I'm trashed for the next few days. And I can only do workouts like that for 3 weeks, then I need a break.

I can ride Z2 for however long I feel, whenever I feel like it - and never get tired or burnt out.

Who knows really what that crossover point is? Obviously for pro level riders - they have enough volume for Z2 to matter. What is that number for us duffers?

In that other Z2 thread, I linked to this recent paper on "moderate intensity" (that is, not Z2) training: https://pubmed.ncbi.nlm.nih.gov/40101160/

That's nice. Now how did cycling performance compare?

It's all about a balance. I'm still trying to find that balance. I tend to believe that too many gym-goers spend way too much time in zone 1/2 and too many Elite/Professional and wannabe elites spend too much time in too high of a zone.

I have come to think that many professionals have slipped into being over-trained, just so slightly, but not enough for it to be noticeable, other than via their "poor" performance. However, that poor performance gets blamed on other things.




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Anybody who thinks that Zone 2 training is junk is completely clueless. Health benefits of Zone 2 are well documented plus I find it extremely pleasurable and fun to spend 3 -.4 hours in Zone 2...I don't ride for performance but even real pros do more Zone 2 than HIIT. Nothing builds and maintains and aerobic base as good as Zone 2.

Oh, I think Z2 is better than nothing. I can't recommend Z2 highly enough.

I kind of think this sentence summarizes the paper; if you have little time to train, you need to do it at higher intensities.

Or to summarize even further, "Duh."

I read it and a couple of sentences jumped out.

"A systematic literature search was not utilized to obtain Zone 2 exercise studies." OK, so this wasn't a controlled trial.
"we were able to find few studies that explicitly prescribed Zone 2 exercise". Hmmmm
"Few studies have explicitly investigated the impact of Zone 2 training on mitochondrial outcomes and the available evi dence is mixed. In support of Zone 2 training improving mitochondrial capacity"
"10 weeks of twice-weekly training at an exercise intensity corresponding to FATmax—possibly above Zone 2 as discussed below—increased CS activity and mitochondrial respiration in obese individuals with type 2 diabetes mellitus"

Really not helpful.

I think a lot of this is psychological. If a doctor needs to tell you to work out, she needs to say words that will have the best effect. For many, that is walking. For others, she'll suggest zone two jogging or biking type stuff. For those that already jog or bike, perhaps she'll mention adding in some more strenuous exercise.

So even if the article is correct, zone two is still lets say 90% as good, while being a lot easier for many folks to commit to.

Also, zone two is "Low intensity steady state", meaning a person could sustain it all day. By definition, you can't sustain the higher zones all day. So if you want to train a lot, your only choice is zone two.

I'm starting to have second thoughts on the idea of, "consistency". It seems to me that people are too wrapped up about cardio fitness, period. So if one is a runner or cyclist they seem to see this idea of consistency as needing to do that activity virtually everyday and that's where this thing about zone 2 comes into play, because if you go above Z2 every time you go for a run/ride that would lead to wearing something down, whether it involve you musculoskeletal system or your nervous system.

I'm coming around to the idea that we all talk about consistency, but it's not well defined. When does consistency, even at low levels, becomes too much? Is there such a thing? I think so.

I do believe for many people in their quest to be consistent causes them to mainly do that one activity. I'm not saying that you will suffer a direct injury to your musculoskeletal/nervous system. doing that one activity. However, you will experience degradation to other areas of your musculoskeletal system and I think, given how complex our body is, it will manifest in many ways.

I could go on for a while here, but I'm going to cut it short. I've given up on the idea of consistency on the bike/run. and now I've decided to vary my workouts much more and focus on things that are difficult and because of that are enjoyable at creating challenges and obtaining goals. I'm no longer worrying about my cardio zone, because whatever I do my cardio is getting exercised. But what is more important is that I'm exercising my entire musculoskeletal system.

Just look around at all the old people and what do you see. Non-mobility. I even know runners and cyclists that are becoming immobile. I don't believe that's natural, rather it's from our way of living and just cycling or running may keep those effects away a little longer, it will eventually catch up.


Here's a short video on the surge of American caregivers. My sister and I fall into this category and it's not fun. I will NOT allow myself to burden my family as I age.

Zone 2 has lots of things going for it:

1. It's pleasurable.
2. It burns calories.
3. It helps you with your tan.
4. It gives you something to do between harder training days.
5. It lets you chat away with your riding buddies.
6. It gets your body accustomed to lots of time in the same position.

Is it the *optimal* way to make you stronger or faster or more efficient?

• increased plasma volume: no
• increased mitochondria: no
• increased lactate threshold: no
• increased muscle glycogen storage: no
• hypertrophy of type 1 muscle: no
• muscle capillarization: no
• increased VO2max: no

"Optimal?" Maybe, maybe not. Consider the following:

I'm substantially older than most college students; as a matter of fact, I have a lot more time to train since I retired, unlike the average college student (and, in all likelihood, study participants!). And my conditioning, alas, is likely much lower than the study participants'. So if I posit "optimal" means increasing plasma volume, mitochondria, lactate threshold, muscle glycogen storage, etc. over calendar time (say, by then start of next summer), what's "optimal?" Should I spend 6 months riding 2-4 hours daily in zone 2, and adding in intervals and threshold training after maybe 4 months of zone 2 riding? Or would two half-hour interval sessions weekly be better for getting into shape for next summer?

I don't know whether to cut the study authors some slack, or not. On the one hand, it's a lot easier (and cheaper) to find some college wanna-be-athletes and drive them for half a semester, than it is to do a longer, slower study with more participants, and try to do a decent job of data analysis to pull information out of all the noise such a study would generate. On the other, my impression is that the lit search was rather slap-dash -- like what a junior professor would have some "Introduction to Science and Analysis" students do in a one semester class.

I remember a video with Pogacar (early 2025 maybe), can't remember the YT channel now, they asked him about his training, it was 20/25 hours per week, mostly zone 2, including long rides (4-5 hours when possible), but of course also shorter rides/intervals at high intensity.

He was asked what he would do if he couldn't ride that much, like most dads and 9/5, who only have a couple of hours, and said he would probably do HIT instead, several shorter sessions spread on the week with rest days in between.

My guess is it depends on your age, health condition, and what is the purpose of your training... My understanding is that at least 1-2 x 50 minutes of zone 2 (or longer) and 1-2 x 15 minutes high intensity should be close to the best health benefits you can get (I'm not talking about performances or competition, here).

I find constant zone 2 hard and generally somewhat boring. I shoot for the talk test and try to set a level of effort just where speech is starting to be affected (VT1). What I would really like is a team car following me with a lactate meter and I would stop at prescribed times and test blood lactate to adjust power. I thought about a buying a lactate meter and performing loops around a local island with my car parked on the route and I would stop and perform a lactate blood test and then adjust my power. Pretty geeky and it seemed like a pain in the ass.

I find constant power with no stopping at zone 2 very hard. However, I think is supports the other energy producing systems that require different muscle fibers that generate more lactate. Slow twitch muscle fibers with well developed mitochondria (constant power efforts) will burn the lactate produced when riding tempo power and higher.

I can only imagine what it is like for the UCI world tour and continental pros that ride hours at constant power with cars following them with lactate meters making sure they are at the most efficient lactate level - brutal.

I will take intervals any day over long constant zone 2 riding.

What about noodling around at an easy power with stop signs and traffic lights and taking short breaks on or off the bike? Why not? I will call that sort of junky but not insignificant.

IMO, planning any riding is about the goal. If the goal is hard, such as back to back to back days in the mountains riding with hitters, then I need a lot of hours on the bike at zone 2 with supporting, VO2, threshold and tempo riding with a lot of climbing. And some of the riding can be noodling around at low z2/z1.

How to train, particularly for elite athletes with lots of time, has been generally known for the last 50 years. Mostly easy with lots of volume. One or two intense sessions per week that are hard, but not crazy. Every so often, really go deep.

None of this stuff is new, or revolutionary. It's been largely settled science since the 70s, or perhaps even earlier. The things that are actually debated are the details.

The big benefit of easy (or "zone 2") is that you can do a lot of it and still recover. Volume matters. No reasonable person thinks 1 hour of easy work is the same as 1 hour of threshold though. A time crunched athlete is obviously going to cut the easy stuff first.