I haven't used any of the Garmin optical HR devices, and would be a bit skeptical of wrist based devices unless very well fitted. However, it's not essential to use a chest strap to get decent data. I have used a Scosche Rhythm+ for the last 4 years with incredibly few issues. I used Garmin straps for years and had far more instances with various versions of the Garmin chest straps giving spurious data due to poor contact than I have ever had issues with the Scosche. However I wear mine on the front of my upper arm, just above the bicep (secure but not tight). It didn't work nearly as well on the lower arm or anywhere else I tried.
I hate chest straps for running, they tend to move south on me - I blame my triangular, muscular physique ;). However they were always fine on the bike. So for a while I stuck with the chest strap on the bike, thinking it was better, and just used the Scosche for running, but eventually I ditched the chest strap as the Scosche was proving rock solid.

Out of curiosity, how did pace of these two runs compare to the HR chart you posted earlier? Is the lower HR because of the HRM (optical vs chest strap as hypothesized by some) or because you've slowed down?

BTW, i'm another in the camp that lots of slow easy miles should not be underestimated. It's not really until you're running 5 or 6 days week putting up 40-50+ miles per week that marginal benefits and risks of running injury that come with speed work overcome the benefits of adding more easy miles. Even at that kind of running volume, add the speed in slowly and keep a vigilant eye of injury.

The pace of the HR chart I posted yesterday was a 10 mile run at 7:52 avg pace. This was my old schedule:

Mon: 5 miles under 8 minute pace
Tue: Speed work: 1 mile warm up, 8X400m @ fastest pace (5:50 to 6:30 pace) with 30 sec break in between, 1 mile cool down
Thurs: 6.2 miles under 8 minute pace
Fri: 1 mile warm up, 12x400m HIIT training (run a lap, do 12 pullups, run a lap, do 25 pushups, repeat), 1 mile cool down
Sun: 10 miles under 8 minute pace

Basically I have been doing speed work to try and get comfortable running at faster pace. Then I run everything else hard as well to try and drop my average pace.

Zone 2 training was appealing to me because I liked the idea of being able to run 8 minute pace at zone 2 instead of zone 4. Also I have an issue with my legs cramping after mile 15-17 so I hoped that building my base would help with that.

My thought was to do the following:
Mon: 6.2 miles in zone 2
Tue: 6.2 miles in zone 2
Wed: 6.2 miles in zone 2
Thurs: 6.2 miles in zone 2
Fri: 6.2 miles of tempo/speed/intervals
Sun: 8-10 miles in zone 2

I know I'm adding mileage but I'm doing these 10ks so slow (3:00 per mile slower), that I'm not really tired after the run. Running this slow is frustrating but I've read that was the hardest part. If you stick with it and build your base, your pace will increase and you'll continue to stay in zone 2.

Again, how did you determine your zones?

If you can actually run your prior mileage at that pace, I suspect that your zones are currently incorrectly calculated - with your kind of volume and speed, zone 2 should not feel super slow, nor probably should it be10:30/mile.

I run barely 8:30/mi for my 'faster' zone 2, and I run 5ks easily under sub20 and 10ks about 40 flat. Per your 800 interval paces (which should be slightly faster than 5k pace), you should be equal or only a hair slower than me, since I run my 800s at your paces (5:50-6:30/mi). My 8:30/mi for zone 2 actually feels somewhat challenging too, for sure it's not 'gawd this is so slow!" - I'm usually feeling 'man, z2 is annoying brisk now!'

I strongly suspect your zone calculations are really off. Redo your zones with the HRM strap, get a field tested HRmax or some other field test HR value, and check that the data is good. I'm positive you won't be complaining about super slow z2s anymore.

That'll work great. Good luck.

Curious as to what your running race times or tri run splits are? Would also help correlate, as if you are a 40 flat 10k runner, 10:30/mi z2 makes no sense, whereas if you are a 50+ min 10k runner, it's a lot more reasonable.

Very interesting. I did not know that Scosche. Does it work just like a chest strap? With a coin-battery? I might buy one.

I am in a similar situation to you although maybe some weeks down the road, so I will give some info on my experience.

2 years ago I took up running frequently. I did almost every run at a fast pace. I got better until I hit a wall at breaking the 20min 5k.
Last year I switched my approach to more slow, long runs to prepare for my first marathon. In the beginning I could not keep running at 75% maxHF. I had to stop and walk to bring my HR down. At 70% maxHF I ran like 12 minute miles. Just running slow allowed me to get better at running for hours on end and allowed me to finish my first marathon, but I did not necessarily get any faster. My volume was also a bit on the low side in hindsight.
This year I do a lot of running and biking at low intensity, bit more than last year. I am now faster at 70% maxHR than last year at almost 80%. With almost no speed work, except on the bike.
I am now adding speed work back to running again. Not yet at 20% of weekly time spent because it is very taxing, but I already see gains. My repeat pace is going down, and my pace at low HR also starts to creep down. I am not yet at the 20min 5k, but my trajectory and progress tells me that I soon will be.

To sum up, switching to almost exclusively Z2 work allowed me to build a good base I can work from. I think I needed that coming from mostly high intensity work.

My personal suggestion for you is to commit to mostly Z2 work and increased volume for a couple of weeks before adding in intensity again. It will change your view on running a bit, and probably help to bring down the HR during slower runs quickly. You also have goodie down the road of getting to do quicker runs as well. Just don't wait over a year to introduce it back like I did.

Well maxHR results are in. I did three different tests and my maxHR got to 184. Considering I'm 38, that isn't too bad.

I just don't really know where that would put me in terms of zones.

My HR zones based on Garmin are as follows:
Z1: 50-60% max HR: 92 - 119
Z2: 60-70% max HR: 110 - 128
Z3: 70-80% max HR: 129 - 146
Z4: 80-90% max HR: 147 - 165
Z5: 90-100% max HR: 166 +

I did research on Maffetone training and that calculation had my zones set too:
Z1: 49-59% max HR: 93 - 111
Z2: 59-75% max HR: 112 - 142
Z3: 75-85% max HR: 143 - 161
Z4: 85-91% max HR: 161 - 172
Z5: 91-100% max HR: 172 +

I just don't think the Garmin is right. Today I ran a mile at my 7:50 - 8:00 per mile pace and my heart rate was at 166 - 170 the whole time. According to Garmin that would put me in zone 5 but I can run that pace for 13 miles.

Something sounds really off with your HRM, honestly. Even you can tell something is way off with it, as the numbers make no sense by any standard. Time to get a new one.

I don't think the HRM is the issue. The HRM on my wrist gave me the same HR when running that pace. I think what Garmin has as my zones are not correct. The Maffetone zones seems a little better to me. Zone 5 starting at 172 instead of 166 feels more reasonable. I can do around 170 and feel like I'm pushing myself but it's something I can hold for a long time. That's the way I've always ran so I think my body is use to running that way. I've attached my pace and HR from this morning.

Well maxHR results are in. I did three different tests and my maxHR got to 184. Considering I'm 38, that isn't too bad.

I just don't really know where that would put me in terms of zones.

My HR zones based on Garmin are as follows:
Z1: 50-60% max HR: 92 - 119
Z2: 60-70% max HR: 110 - 128
Z3: 70-80% max HR: 129 - 146
Z4: 80-90% max HR: 147 - 165
Z5: 90-100% max HR: 166 +

I did research on Maffetone training and that calculation had my zones set too:
Z1: 49-59% max HR: 93 - 111
Z2: 59-75% max HR: 112 - 142
Z3: 75-85% max HR: 143 - 161
Z4: 85-91% max HR: 161 - 172
Z5: 91-100% max HR: 172 +

I just don't think the Garmin is right. Today I ran a mile at my 7:50 - 8:00 per mile pace and my heart rate was at 166 - 170 the whole time. According to Garmin that would put me in zone 5 but I can run that pace for 13 miles.