Intensity- how low is too low for aerobic development?

Because that's a completely ridiculous and unrealistic "goal."

That's a dream, not a goal.

A goal would be to break 21:00. Then 20:00. Then 19:00.

And the workouts would progress as fitness improves.

See, you didn’t say that I can’t set an unrealistic goal. I see people in my area doing exactly that. They run one time and want to train for an unrealistic goal time.

So we agree that workouts need to be progressive and slowly build as fitness improves. I prefer to use data and evidence rather than guessing. That’s where you and I differ.

Speedwork is all about guesswork though. Can I run this next rep 5 seconds faster? Can I do the next mile 2 secs a lap faster? Its learning when to be aggressive, when to hang on, and when to back off. There are no scientists hanging out on the track during your repeats or at the top of the hill for hill work. Until you get to elite level, its all guesswork with just a general idea when you start a session.

The goal of easy runs is to get the most mileage you can without compromising these sessions while getting the heart to a reasonable level. IE, you shouldn't generally replace an easy run with a hike and if you're feeling good maybe you need to pick it up or do more in your workouts. The question should be how slow can I run and still MAXIMIZE improvements, not how slow can I run and still improve.

Your approach to tracing is not like any of the coaches I’ve spoken with. It’s not guess work. It’s deliver trial and error. That’s completely different.

You don’t have to guess if you don’t want to. You can establish your current limits (fitness) and train to your current fitness. Even Jack Daniels says to train at current fitness.

I don't think this is an issue only for beginners. I suspect many 19/20 min 5K runners cannot run at circa 60% of max hr. Is this maybe holding them back?

First, I’d like to say, I do agree that multiple trials/results at a variety of distances would be preferable to one race. I also like what I think you are implying, that the results from a race are generally the result of an effort in a tapered state so that does not reflect the typically fatigued state that training will take place in.

While I generally can't hit a 5km - 10km race time during a time trial (I'm normally 3-5 sec per km slower) the effort certainly feels about the same, so I don't know that I feel the internal load is all that different from a race? Meaning, the general stress imposed and resulting fatigue seems marginally discernible, if not equivalent.

I don’t know what specific distances you’re using for your time trials, but if those distances are generally in the severe intensity domain (which if you’re calculating Critical Speed, they presumably would be) you’re still relying on a model that is basing it’s calculation on a zone that is physiologically disconnected from the zone it's extrapolating to. I think that is fair to do, of course. However, if we are focused on the topic of a pace for general aerobic conditioning, you could never run a race and through lab work or a heart rate monitor, know where your LT1 occurs or your 60%-75% HRMax range falls, respectively.

Btw, how are you calculating VO2Max without measuring oxygen consumption? A regression equation?

Excellent, we agree on a method of measuring current fitness by using multiple time trials in as close to the training venue as possible (my opinion added). But it also depends. If you race often and are training a couple days after the race, then it’s ok to use the race data to help model fitness. But if your races take weeks to recover from and you’re only doing light training, then you can detrain 5 to maybe 10% in a few weeks. So getting a current snapshot is important.

I use 0.5 mile and 1.5 mile as my distances for short time trials. Then I run for 40-60 minutes near the estimated CP and get a feel for where my actual threshold is. That usually lowers CP into a more reasonable range with the 40+minute trial. I’ve confirmed with lactate testing that my CP with a long time trial is very very close to mlss.

You don’t need any fancy data to get vt1/lt1 (not the exact thing, but close enough). Most people need to run and have a conversation while running. For lots of runs, too. Then you’ll learn to feel exactly when you’re breathing too hard to get your words out. It’s been quite revealing to run with my partner. I’ve taken him from 0 miles a week, to 45 miles a week in about 18 months. I believe I’ll get him to 60 miles a week by the end of next year. But he’s slowly building speed since he’s new to running but is resistant to running harder intervals. But I digress.

About VO2max, I use a 1.5 mile time trial so I can use the Cooper equation to estimate VO2max. I also have Apple Watch and Garmin estimates. I also do a step test at the track to get regressions for hr, lactate, pace, and power from which I can estimate VO2max, pvo2max, vvo2max with my known max heart rate. Oh, and I also use a portable metabolic cart to measure. All of my estimates come within about 3 ml/min/kg. Not a bad spread.

How low is too low? That was the original question. I maintain that for the seasoned runner (and that’s an important distinction because the physiology for a newbie is not the same in terms of mitochondrial content and capillarization) you can run too slow if the purpose is to recover and still achieve an aerobic stimulus.

If a 17:00 5K runner runs at 9:30 pace on a recovery day, that is pure junk mileage. They’d be better off taking the day off or cross training. However, if that same runner runs at 7:30 pace and regulates the duration of that run to make sure the run remains in the easy zone in terms of total stress, that pace will provide an aerobic stimulus that is not entirely negligible.

Somewhere along the line we mixed up the concept of base training with long, slow distance. Base training speaks more to the reduction of very hard running. It doesn’t mean plodding around. I’ve coached runners that have needed to do that for a while when they were coming back from a long layoff, just starting out, or were already coming to me in an overtrained state but I do not take that to be the subject of this thread.

As Kvothe said, 5K + 2 min is not that fast. I use it as a lower bound, plus or minus slight variation depending on how one feels. If you find that pace range difficult, I’d be somewhat concerned. I’d look at how you are piecing together all the other components of training. If you are running considerably faster than 5K + 2 min on your easy days (there are some who can do that, very high proportion slow-twitch and best suited for the marathon) just tread with caution.

You and I don't differ because you and I haven't responded to each other prior to this post.

You gave a bad example. I just called said bad example "bad."

I averaged 39 mpw for the last 10 weeks prior to my 5K PB (16:57) doing most of my easy runs in the 8:51-9:40 min/mile range.

To claim that those were junk miles and that I would've run faster if I was in the 7:30 min/mile range is just wishful thinking.

I've learned to let my body dictate how easy is easy. It could be closer to 8:00 min/mile on a good day with good weather conditions. It could be closer to 10:00 min/mile on a worse one.

I only know how fast, or rather slow I went on an easy/recovery day after I finish the run.

This is a great post and puts things into context. I've enjoyed your posts in the famous Norwegian singles thread. I think that is worth a read for everyone commenting here. I think that is such a good thread for a number of reasons, but what is quite shocking I think to most, is how easy the easy days, when you plug your times in. Someone made a spreadsheet on Strava based on the suggestions made in page 1 of that thread and the Easy pace is truly shocking to me, in terms of how slow it is, yet following sirpoc and others from that thread on Strava, they all seem to have shown remarkable improvement and are looking like aerobic monsters, right up to HM.

I would imagine the vast majority of people were already doing their easy runs, too fast, thus impacting their workouts in the medium to long run. I feel like this is something that might catch up with you around the middle to end of day a Daniels training block, but I'm starting to change my thinking of 25-30 years to longer than just specific training blocks and that we should be thinking about getting in as much sustainability as we can, all year round. I truly believe that running easy might be the key to unlocking that, having read said Norwegian thread.

I've been jogging 9-10 minutes per mile for 30 mpw and I'm back in 17 shape. My heart rate is elevated by jogging up lots of big hills. 5'10 140 lbs 35 yo.

Downvoted by a fat middle aged runner no doubt. I will soon be back in 16 shape whilst still jogging my runs.

We don’t have to be so quick to agree. A little dissent makes the exchange more interesting haha. Though I may not see the point in calculating ALL of those various metrics you listed, I certainly appreciate the interest in them and making use of them for predicting both race paces and training paces.

As it pertains to this thread, perhaps you could share once you have your critical speed estimated, what percentage are you using for establishing the easy pace range on the high and low end?

Btw, regarding critical speed, it appears you're not using the 3-5 test protocol? Is there a reason you do the 800m and 2400m with the 40-60 minute tempo effort in place of an extra 1-2 time trials in the say, 800m-4800m range?

All this just to arrive at Lydiard’s “Miles Make Champions.”

All of those metrics are trivial to calculate and can be tracked over time. So I see no reason not to track all of the data :) I do the same 2-3 workouts at the track every couple months and can control many variables.

I actually use lactate to delineate the upper end of my easy zone. But the lactate just told me what I already knew by breathing. I’ve also used Dfa-alpha1 as a method of estimating the upper end of the easy zone. It kind of works, too. For the lower end, I’ve learned that there is a too slow, and that’s only by trial and error. But I’m already at 12:00/mile on very slow days. I can shuffle along as slow as 14-15/mile, but that’s barely working.

For CS I use at least three trials. You can use from 2-5, but more trials doesn’t necessarily mean a more accurate CS. I also use four different models to estimate CS/D’ and CP/W’. By the way, my 40+ minute trial is a max effort, not tempo! I do 60 minute max effort on the bike. Also, I do 800m and 2400m simply because those distances are around 3 minutes and 10 minutes for me. Typical times for a quick and dirty CP/CS estimate to base the 40+minute max effort.

pubmed.ncbi.nlm.nih.gov

Critical power: How different protocols and models affect its determination - PubMed

Estimations from CP3-hyp were found to be the most accurate, independently of TTE range. Models that include two trials between 12 and 20min provide good agreement with the criterion method (for both CP and W').

Open link

Oh, my easy pace range is roughly 60-80% of CP/CS.

This is absolute and total overkill. Bordering on total madness.

Many will find an easy pace of 5k plus 2 mins, very easy and sustainable. However, this metric is wholly arbitrary. Others may be getting closer to the high end of the easy zone with this pace, and it will restrict their volume.

You appear to be arguing that it is fine for volume to be limited by an arbitrary easy pace.

Every study shows that volume is critical, and easy running is the area to build the volume. It doesn’t make sense to limit volume by running at an easy pace that some may find unsustainable for large volume.

5k plus 2 mins is not the same for everyone. 2 mins will be near 50% of the mile pace for a 13 min 5k. But, nearer 33% of mile pace for a 20 min 5k. There is no logic in saying that anything slower than an arbitrary pace is junk miles. I am very much interested in the concept of junk miles, but where is the science for this?

Using marathon pace with an add on, would be better than 5k pace.