Long run in zone 1 or zone 2?

I dont' know the answer, but I know Z1 for me is dang near walking and seems to take a lot more energy than running faster.

I end up doing my long runs in zone 3 bouncing between 140-150 bpm, but I really just go off of RPE so sometimes it's higher and sometimes it's lower.

2,3,4,5

whatever i feel like....

My approach:

Generally I want to go as hard as I can consistent with being recovered to continue running the next day (or whenever I plan to run next, which is generally the next day).

'Hard as I can' doesn't necessarily mean the same effort all the way.  I might, for example, do a progression run, or make some portion of the run 'tempo', but I don't avoid making my long runs hard.  On the contrary.

If I feel so rotten that I would be forced to run z1, I would move the long run to another day or just skip it.

Sometimes I have to run a bit to know whether I'm feeling rotten.  Especially when I'm running a lot, it can take an awfully long time for me to start feeling good.  That's fine.  So there have been a few days when I have planned to run long even though I start off feeling bad.  I run easy for a while.  If, after an hour or so, I still feel that harder running is not in the cards, I stop, hoping to do the long run the next day instead.  (In reality, I can usually tell within the first 20-30 minutes whether it is going to get better.)  But usually I feel fine after an hour (or less) and then I can pick it up for the rest of the time.

Don Fink's Be Iron Fit plan calls for a Zone 1 or Zone 2 long run on Sundays.  I just completed IM Louisville and did all my long runs in Zone 2 with the end of the run sneaking up to Zone 3.  My understanding of Zone 1 would have me going so slow that I would be uncomfortable and lacking form.  Heck, I would look more like the teenager that pretends to be trying to get out of your way in a parking lot.  You know what I mean...fake "jogs", but is actually going slower than if he were walking.  that's what I look like in Zone 1.  Ha!

I follow Joe Friel's plan.  He has you doing Long runs in either Zone 1 or lower end of Zone 2 for the first 12 weeks of Base period, then moving it to upper Zone 2 for the Build periods.

Without knowing your heart rates and just going from the chart, a 20:00 5k runner would be at about 9:00/mi in Zone 1.  A 22:30 5 K runner would be at about 10:00/mi in Zone 1.  Those are certainly runnable paces, but if you get much slower than that Zone 1 dips into 11 and 12 minute miles and I don't see how that's really productive at all.  Maybe that's why he allows going into lower Zone 2.  Or maybe he's factoring walking breaks if you are down in those slower times.

   Thanks for all the advice.  I think I will skip the zone 1 and try out a long run in a low (or high, if it feels ok) zone 2.  When I run at a comfortable pace it tends to be a high zone 2/low zone 3.  I am focusing solely on running right now and plan to do OLY tris all next year. 

   I would run by feel all of the time, but I have limited training time and want to make the most of it.  I have learned that it helps to have a goal for every run.  Mine right now being either working on endurance (which would be long zone 2 runs as I see it now) or increasing lactate threshold pace (which would be zone 4 work from my understanding). 

   It is good to hear other people say that zone 1 seems "worthless" to them too. 

Just to be clear -- it isn't necessary worthless.  Under the right circumstances, it can be used for recovery.  That said, recovery running is (IME) helpful only if you are running a lot.  If you aren't, it is better to use easy cycling for your active recovery.

I think there's a danger of over-thinking this. There are no magic numbers that will lead your body to optimal adaptations. At least not at the level that most of us here are operating at. The relevant adaptations will occur with a wide range of training stimuli, and the biggest bang for our buck tends to come from whatever allows us to stay consistent. If you run at a comfortable pace that allows you to accumulate reasonable volume, endurance will build. Hitting exact HR zones won't make much of a difference. And adaptations of LT and V02max can also occur across a wide range of workouts. If it's an effort that you can maintain for more than a few minutes but not more than an hour, then you're in about the right range.

Echoing Michael: Zone 1 isn't worthless. You'll know it when you need it (as I learned recently), but most of us don't need it very often. 

I'm just going to give you the benefit of the doubt and assume that you meant to leave '42' out of it.

(OK, but seriously, great post, and I agree entirely, especially the part about doing whatever allows one to stay consistent.)

I agree with this.  I copied an pasted a graph from my garmin hr data.  I hope this helps you with your decision.  This was an 18 mile run last month.