Chicago Marathon 2013 - Matt Aaronson - GREAT RACE!!
The short version of this report is that I ran my first marathon today – the Chicago Marathon with all of the hoopla and 45,000 runners – in 2:57:47 (6:47 pace officially). The race that exceeded all of my expectations for the marathon experience. The weather was perfect (perfect enough that the guy who won crushed the course record and came within 20 sec of a new world record) and I executed almost exactly according to my gameplan and ran extremely even splits all the way to the end. I felt great throughout the whole race. My legs started to get tired around mile 19 and my pace probably faded a couple of seconds per mile but hard to say because at a couple of points after mile 19 I walked a few of the aid stations to make sure I got some water down and not up my nose. But my HR was nice and low and I had a ton of aerobic capacity up to the very end. I knew there would be a headwind for the last 2.5 miles but I was mentally prepared for that and when I saw that I could beat 2:58 I accelerated substantially and ran mile 25 in 6:29 and the last ~quarter mile at 6:03 pace to squeak in with 13 sec to spare. I'll be paying for that tomorrow, though...my legs were toast and really aching now and my feet are killing from the racing shoes that I so rarely wear. One of the defining moments for my race might have been at mile 2 when I ran up behind a training buddy who is much faster than me…he probably saved my race by telling me to slow down big time. I ran mile 3 with him at slower than 7:10 pace and it got my HR down and allowed me to settle into a good pace. So a big success and I'm super-happy with the result.
Garmin file: http://connect.garmin.com/act...698
Now a few more details for those inclined to read a bit more…
I'll spare you all the details of my training leading up to this race although that is an interesting discussion I'll start in another thread. The quick background is that I had a shortened tri season due to the birth of our third daughter and the need to do something without the time-intensiveness of cycling. Since I had done the half-ironman world championships in Vegas twice already in 2011 and 2012 I wasn't so disappointed and focused on the new challenge of training for my first ever marathon. It is amazing how you can run 60+ miles a week and have so much time on your hands compared to doing tri training! My training was very consistent other than getting sick for about a month starting in late August with a cough that turned out to be reasonably bad bronchitis requiring antibiotics (which I could have figured out earlier if I had got myself to the doctor). But I didn't miss any workouts and in general I had very few failed workouts over the course of the training.
My goal for the marathon was to run to my capabilities (fitness+execution). After running a 1:26:10 half marathon in the spring I figured sub-3 hours was a possibility, but on the edge of my capabilities. It would require perfect execution, perfect weather and conditions, and a little luck. Mostly I wanted to walk away from the marathon experience saying that I had run my best race and the result reflected what I ought to expect. But I trained with a 3-hour pace target and that was roughly where I was expecting to end up.
For the first time I decided to commit a race plan to paper. I'm not sure why exactly, but I guess I was really focused on not botching the execution after hearing so many stories of people running a great race up until mile 20 then having the wheels come off. In any case I drew up a really detailed plan (http://members.endurancenatio...spx) and got a ton of great comments from you wonderful teammates. Almost all of the deviations from my plan were the ones you all recommended (e.g. Rachel, I didn't go to the CARA hotel…Robert, I went with 4 gels and not 5…etc). Then, I followed the plan…
- No workouts Thursday or Friday
- Picked up my packet on Friday after work. Boy does the expo for a 45,000 person mainstream running event kick the crap out of a triathlon "expo"!!!
- At the expo I picked up (for free) a "pace tat"…a temporary tattoo of the target splits for a 3 hour marathon. The night before the race I cut it in half and put the splits for the second half of the race on the inside of my forearm. Pretty cool little thing.
- Slept for almost 10 hours on Friday after taking 2 Advil PM to ensure a restful night.
- Saturday I did a 2 mile run in the morning with 4x30" strides. . Felt a bit sluggish but probably that's the taper, and maybe the remnants of the Advil PM. Then I stayed off my feet for the most part. I ate some pancakes after the run and had paella for a late lunch. But not a ridiculous amount. I had a very light dinner, ~700 cals of pasta with some olive oil and garlic and ended the day with ~3000 cals but not a ton of food after 2pm. Drank 3x 20oz bottles of G2 during the day too.
- Tossed and turned trying to sleep on Saturday as expected, and was up at midnight so I ate a 250 cal powerbar to top up the glycogen stores. Eventually I must have drifted off but it was not a great sleep and I woke up before the 5:45am alarm.
- Weighed myself and was concerned but totally unsurprised to see the scale showing 141.5, or about 3.5-4 lb above my weight for the past month. But I trusted that this was the carbohydrates and the water stored with them, and in any case no sense in worrying what you can't control on raceday…
- After getting my clothes on and getting a coffee I got in a taxi down to the race. Since I had no gear to check I bypassed the massive lines to enter the start corral area and got in via the "express lane". By 6:20am I had already used a porta-potty with no line and was sitting under a tree in the 55-degree weather eating a few shot bloks and watching the energy build as more people arrived and the crowds built up. I used the porta-potty once more then got up for my warmup.
- Based on the layout of the start corral area it was pretty clear I'd be unable to do the 5-minute warmup I had planned on, so instead I just jogged around a bit or grass where others were trying to do the same. It was pretty lame but got my HR up a bit and I wasn't too concerned because I'd have a bunch of time to settle into my pace once the marathon got started.
- By 7:10am were we all loaded into the corrals. I was in the "A" corral right up front. The PA system kept cutting out during the national anthem so everyone started singing it which I found quite moving. Then the wheelchair athletes started and it was gametime for the runners…..
- The first mile I just tried to stay out of the crush of people and it wasn't too bad. Within a quarter mile the course goes into a tunnel that seriously messes with the GPS so I was just going with the flow, pace-wise. I took a split at the first mile marker and it was 6:42 which was not too bad…it could have easily been faster if I let things get out of hand. At that point I also took note of my watch time vs. the clock time to know that I had crossed the start line 10 seconds after the official start. Always good to know how much your chip time lags that of the official clock!
- Halfway through the second mile I was starting to speed up. I didn't have my HR on my Garmin screen but now looking at the data I see that at that point 10 minutes into the race it was higher than at any point up to the final few miles of the race. Amazingly in the massive crowd of people I ran up behind a guy who is part of the running group I join on Saturday for long runs. This guy just ran a 1:21 half marathon and I was expecting big things from him. I pulled up alongside him and we started to talk and he said we need to slow down. When we passed the 2 mile mark I said we ran it in 6:39 and he immediately reacted with "we have to slow down more". I followed his lead and we ran the next mile at slower than 7:00 pace. People were just flying by us. But it felt so good to slow down at that point. I later saw that my HR recovered substantially and I was just feeling great.
- At around the 5k my split was 21:03, right on target, and I started to pull away from my buddy, mostly because I could hear the 3:00 pace group marching up behind us and I really didn't want to get swallowed up by them. But I was totally "settled in" at that point, and from then on I felt awesome.
- Per the plan, after the 5k I changed to the second screen on my Garmin which would remain on for the remainder of the race. Lap average pace in big font, then in smaller font the current HR and current cadence
- Looking at my Garmin file I clearly forgot to take a split at the mile 4 marker, but in any case I was pretty much in the zone running north from the 5k point up to the street where there is a turn back south at mile 7.5. As expected there was a headwind so I tried to draft off of some guys with questionable success. I was able to follow one pretty big guy for a while but it was tough to find folks running the same speed and I really didn't think there was benefit in speeding up substantially at that point to get some drafting efficiency. Splits: 6:36 (for miles 4/5), 6:41, 6:37
- After the southbound turn the plan was to bank a bit of time between here and the halfway point given the tailwind. I did that although was a bit more restrained than I might have otherwise been, given the earlier run-in with my buddy at mile 2. I saw my family at mile 8.75 and they were right where they said they'd be, so I gave them a goo shout-out. Splits were very consistent: 6:42, 6:43, 6:46, 6:44, 6:42, 6:42. I was feeling great. My split at the half was 1:28:36 which is EXACTLY on schedule per my race plan.
- I took gels at around miles 5 and 9.5 according to the plan. I wasn't feeling the chocolate but I only had 3 Roctane cherry-lime so forced down a chocolate which would enable me to use the Roctanes for the rest of the race
- Miles 14 through 16 passed without issue: 6:38, 6:44, 6:43. I took a gel at mile 15. I kept thinking about Coach P's reply to one of my posts where he said mile 16 is when you start to really work, so I was waiting for that to happen. Around this point my buddy same cruising by. He looked to be running around 6:30's. I said hi and briefly contemplated trying to keep up but things were going really well and I didn't want to start getting aggressive at mile 16. I knew I was enough ahead of schedule at this point that I could start running 7's and make 3 hours, but an implosion was still possibly if I got greedy. This might be where if I had more marathon experience I could have gained a bit. But maybe not.
- Miles 17 to 19 also passed without issue: 6:42, 6:48, 6:42
- At around mile 19 my legs started to feel tired. I was feeling awesome aerobically – I could have talked someone's ear off if they wanted. But for sure at this point I was "feeling it" and "starting to work". I knew I could afford to slow down and still make 3 hours but I didn't really want that to happen. That said, I didn't want to really feel like I was hurting until later in the race. So I kept the same level of effort and accepted a slight pace reduction. This was exactly what Al T and others had led me to expect – same effort, slower pace. At this point I was working for sure.
- Splits from 20 to 24: 6:50, 6:50, 6:43, 6:50, 6:54. Notwithstanding the data, I wasn't slowing down quite that much. In two of those miles I stopped and walked a few steps at the aid station to make sure I got some water down. When I got to mile 20 I made sure to mentally rehash some of the phrases from the Pfitzinger book about reaching mile 20: "This is what the marathon is all about. This is the stretch that poorly prepared marathoners fear and well-prepared marathoners relish". So I was going to relish it!!
- Also from Pfitzinger: "The key from 20 miles to the finish is to push as hard as you can without having disaster strike in the form of a cramp or very tight muscles…you need to use your body's feedback to determine just how hard you can push…this is a progressive meting-out process, in which you can take progressively greater risks as the finish line nears". Well given my lack of marathon experience and the fact I had my sub-3 in the bag by now short of "disaster striking", I didn't start the meting-out until around after mile 23. But at that point I did my time-check and saw that 2:57:x was on the table if I could keep the speed up. So hey, time to start meting-out…
- At mile 23.5 the course turns north onto Michigan Avenue and goes straight up that street until a short jog to the right with only about 500m to go. So it is a long stretch, and I knew for a long time before the race that we were likely to have a headwind. I was determined that no matter what happened in the race I would not fade over that portion. I seriously visualized that. I was ready for it. I didn't plan on accelerating that portion a ton but now with 2:58 as a possibility I went for it.
- I ran mile 25 in 6:44 and really felt fine and was steadily accelerating. By mile 25 I was running around 6:30 pace and I felt some twitches in my calves. Ah, so this was the "progressive meting-out" in practice I guess. In any case I knew if they cramped up I could jog it in for 3 hours at this point so I kept hammering and ran mile 26 in 6:29, including the hill up Roosevelt Road just before mile 26. I wanted to draft off of some people with the headwind but I was pretty much passing everybody at this point. A few guys screamed by me over this 2-mile stretch but for the most part I was doing the passing. I turned up the finishing chute and fixated on the "finish" banner and running hard to the end. I had visualized fixating on the big clock over the finish and seeing what time I should try to run for in that last 0.2 miles, but as it turned out there were just some very small digital clocks and you could hardly seem them until you got right to the finish line. So I just ran hard and covered the last 0.2 in 6:03 pace.
- I ran looked up at the clock and 2:57 was still showing, so I knew with my extra 10 second I had beaten 2:58. Great stuff!! Then almost immediately I hear someone calling my name. It was David Salzman!! He's an ER doc and was working the finish line. Cool! I chatted with him for a minute then started walking through the finisher area. The area is configured to handle tens of thousands of runners but only around 700 had finished by then so it was pretty deserted. It was also a damn long walk and my feet were starting to be in serious pain…it just came out of nowhere. Then the muscle stiffness hit from nowhere and the next thing you know I look like I'm limping up the road. In any case I go through the finisher area, borrowed a random person's phone to call my wife who had come down with two of the girls and my dad to spectate and pick me up.
Overall this was a great experience and I'm glad I did it. But I'm not sure I need to do it again. I got my sub-3 goal and I'm happy. I'm sure I could go a bit faster and both execution and fitness could yield gains, but not a ton of gains and not a ton faster. So it would be training super-hard to shave teeny-tiny bits off a PR, which doesn't excite me. The triathlons are more fun, better for fitness, and I can compete against people and not only the clock (my sub-3 was good for well over 100th place in my age group today!). I might sign up for Boston in 2015 since it seems like a rite of passage to run the Boston Marathon, but I really doubt I'll train for it as a marathon and am more likely to run it based on a triathlon training program.
The one thing I'll say this experience confirmed is that I tend to race better at longer distances. The new VDOT I got from today's race is 54.3, an all-time high. My lowest VDOTs are in the shorter distances and that makes me an outlier. I seem to be like a diesel locomotive that can soldier on at a pretty constant pace for a long time without slowing down a ton. But my top-end speed just isn't that fast. So it really makes me curious as to how I'd perform in a full-distance ironman one day……………..
Official race splits:
|
Split |
Time Of Day |
Time |
Diff |
min/mile |
miles/h |
|
05K |
07:51:27AM |
00:21:03 |
21:03 |
06:47 |
8.86 |
|
10K |
08:12:21AM |
00:41:57 |
20:54 |
06:44 |
8.92 |
|
15K |
08:33:22AM |
01:02:58 |
21:01 |
06:46 |
8.87 |
|
20K |
08:54:24AM |
01:24:00 |
21:02 |
06:47 |
8.86 |
|
HALF |
08:59:00AM |
01:28:36 |
04:36 |
06:46 |
8.89 |
|
25K |
09:15:29AM |
01:45:05 |
16:29 |
06:48 |
8.83 |
|
30K |
09:36:29AM |
02:06:06 |
21:01 |
06:46 |
8.88 |
|
35K |
09:57:49AM |
02:27:25 |
21:19 |
06:52 |
8.75 |
|
40K |
10:19:07AM |
02:48:43 |
21:18 |
06:52 |
8.75 |
|
Finish |
10:28:11AM |
02:57:47 |
09:04 |
06:39 |
9.03 |
My Garmin splits:
|
Split |
Hours:Minutes:Seconds Time |
Miles Distance |
Minutes per Mile Avg Pace |
|
1 |
6:42.4 |
1.07 |
6:15 |
|
2 |
6:39.3 |
1.01 |
6:35 |
|
3 |
6:59.4 |
0.97 |
7:11 |
|
4 |
13:25.4 |
2.03 |
6:38 |
|
5 |
6:43.6 |
1.01 |
6:41 |
|
6 |
6:44.3 |
1.02 |
6:37 |
|
7 |
6:48.4 |
1.02 |
6:42 |
|
8 |
6:43.1 |
1.00 |
6:43 |
|
9 |
6:50.2 |
1.01 |
6:46 |
|
10 |
6:51.3 |
1.02 |
6:44 |
|
11 |
6:39.4 |
0.99 |
6:42 |
|
12 |
6:42.9 |
0.97 |
6:57 |
|
13 |
6:49.4 |
1.03 |
6:38 |
|
14 |
6:46.5 |
1.01 |
6:44 |
|
15 |
6:48.2 |
1.01 |
6:43 |
|
16 |
6:45.2 |
1.01 |
6:42 |
|
17 |
6:47.3 |
1.00 |
6:48 |
|
18 |
6:44.9 |
1.01 |
6:42 |
|
19 |
6:55.7 |
1.01 |
6:50 |
|
20 |
6:51.1 |
1.00 |
6:50 |
|
21 |
6:49.0 |
1.01 |
6:43 |
|
22 |
6:53.3 |
1.01 |
6:50 |
|
23 |
6:57.9 |
1.01 |
6:54 |
Comments
It's been fun watching your training progress. We have similar running performance with our HIM and half mary PRs very similar. I've often considered going for a sub 3 marathon and this is encouraging for me. That said...I don't particularly enjoy running marathons but your points regarding training time/flexibility are valid and relevant for me as well.
As far as Boston...DO IT! Nothing I've been a part of even comes close to comparing. I had a horrible run in terrible conditions and it was the most fun I've had in an event to date.
Well done and best wishes for speedy recovery.
Interesting comments on your vdot. I would love to see what you could do in a full distance ironman...
Rest up
- Yes, you HAVE to go to Boston. I've been down Ali'i in Kona a few times, but it doesn't compare to the final 6 miles of the Boston Marathon. In Hawaii, it's mostly about, "Wow, I'm finishing the Hawaii Ironman!" In Boston, it's a deafening party for the final 45-60 minutes. You feel like a rock star. I hear you about hating marathons, but the trip to Boylston thru Back Bay is worth it one more time.
- I can't wait to follow you on your IM journey. You have not yet reached your potential. Disipline, consistency, and now you've learned the value of patience, meaning...
- the HARDEST part of an IM or marathon is figuring out and then executing the proper pace at the start (for tri, both the bike and the run). The times I've failed, it was because I didn't have a guardian angel like you did in the first 2-3 miles to slow you down. That lesson will apply no matter how fast you get, every single race you do.
- The second hardest part is letting yourself work progressively harder during the last 40% of the race, just to keep your pace steady. I used Pete P's book also for my marathon career; that must be where I learned that.
Congrats on the sub 3:00 finish, especially as a first ever marathon.
Yes, if you can run Boston you should, at least the 1 time.
The differential between your 1:26HM and 3:57M is just amazing. Then again your now probably capable of sub 1:26 in the HM. Enjoyed watching your thought process, training , and execution from HIM to M this year. Perfectly done to say the least. Your are definitely a diesel engine and would love to see you in an IM. X2 on what others have said about Boston but to me the IM (any of them) is much more special.
What did you eat between the powerbar at midnight and the blocks you had prerace and when?
Enjoy your off-time and then OS. Looking forward to see your plans for next year.
One very nice thing about Boston is that they have corrals based on only 1000 numbers, and the numbers are based on seed times. As a result, more than any other race I've been in, you start with people more or less in your speed group.
For the last years that I have seen you here, you've had a remarkable ability to run a long time at MP/HMP very, very consistently. If/when you do a full IM, you'll need to dial that down a notch, but your ability to run SO steadily will be huge, and you will very likely be able to achieve much closer to your potential the first time out than the rest of us. Witness how you did in your first marathon...which is no joke.
I read your description of "starting to work" and "meeting out" and got flashbacks. No fair for you to write so well. :-)
Matt - those splits are amazing, almost to perfection. The person who races his first marathon with that consistency are few and far between. Great to see your fitness, execution and luck (weather) come together for you.
Like the others have said, you must do Boston, even if just once. It is like no other marathon in the world. You've earned your rightful place, so go relish in it. And I can't wait to see you tackle an IM. You are already such a smart racer.
Congrats!!!
Bravo on a fantastic race. It was awesome to see you at the finish line, for a sub 2:58 Marathon you looked great! Reading about your race was fun, very impressed by the even splitting. Talk to you soon
Again, very well done and by all means run Boston.
Short of a strange scheduling issue it seems clear I'll need to run Boston. If a marathon was on my bucket list then running Boston if I qualified "goes without saying"!
Jeremy, you should totally go for a sub-3 marathon. Seeing your workouts and results it is clearly within your reach if you make it a goal. The good thing is that you're younger than me so you have a few years to get more PBs before your physiology slows you down – you have the luxury of picking a timeframe at some point in the coming few years when you might have less training time available and therefore where run-only training is super-practical. I'll be posting something pretty comprehensive on my training for this race in case it is helpful to you or others.
The tapering comment is right on. I followed a plan for tapering and think the taper made a big difference. Historically I haven't been big on tapering, and have managed to convince myself that "tapering is very individual and I don't need a big taper". For most of my half-irons I've "crash tapered" by just cutting out race week workouts starting the Wednesday before the race. I thought this was working because I set a lot of PBs. But in this race I FELT really good – better and fresher than in most races. My HR for the pace I was running was lower than usual. It's frustrating because I can't attribute that to the taper with any certainty – there could have been many, many other factors and none of them are specifically identifiable. But I do think the taper had a profound impact, and am going to have to factor that into my plans for future races. That is also tough because the temptation not to taper meaningfully for mid-season races is huge given the hole it punches in your training.
Al, yes, patience, consistency and discipline are utterly critical. In training and in racing. My training for this race had only one setback (getting sick for a month!), but overall the training was super-consistent and that was huge. Running 5-6x/week seemed to have a big impact and I credit that (probably along with some strengthening) with not only the fitness, but also the lack of any major injuries. The importance of discipline in execution really can't be overstated. The marathon got me thinking that in my half-irons I'm starting to sub-optimize by getting too aggressive. I need to get back to textbook to get to the next level. If my MP is ~6:45, there's no reason I shouldn't run 1:30 in a half-ironman. The closest I've ever come to that is just a smidge under 1:36, with most of them around 1:38. Sure they were all hot, humid, etc, etc. But I think the real reason is that I was trying to get more of a "could" bike split as I got more confident (and eventually overconfident). So back to patience and discipline…bike 2 mins slower and gain 6 minutes on the run. That plus some swim lessons and I'll have a 4:30 half-iron in my sights…
Tim, I'm sure I could be a bit below 1:26 for a half at this point but not really sure by how much. The new VDOT suggests 1:25:11 and I suspect that's about right with great conditions. A 6:29 pace seems achievable for a half although borderline. I won't have a chance to find out, however, since I'm in offseason mode right now and I suspect I've already lost a quite a bit of fitness between the 2-week taper and this week of recovery (and it'll be almost a week…it's Tuesday night now and my legs are STILL feeling like they ran a marathon recently!). That said, I'm going out to Vegas with my wife who is running the RnR half in mid-November and I'm signed up for the race…but my plan is to run it easy and not race it, and in any case I'm going to start biking a bunch now to get prepped for the OS in January so my running will go down to more typical levels.
As for the food, I didn't eat anything between the midnight powerbar and the pre-race shot bloks. If it was a half-iron I'd have done an Ensure at wakeup and a Clif bar while driving to the race. In fact at 9pm I walked out to the grocery store and bought a Clif bar thinking I'd eat it in the morning. But I wasn't hungry when I got up and realized that before all my long runs I never ate anything other than shot bloks – granted there was an extra hour from wakeup until race time in this case but I was really nervous about making changes to stomach-related things and figured the pure sugar of the shot bloks would be better energy for the race anyway.
I'm really psyched to do a full Ironman at some point and I will certainly try to train and execute with precision and maximize my result. But from what I've gathered, the value of experience in IM racing is huge, so that one might take a few tries to get to a race I can feel was close to my capabilities. In HIM racing I think I'm reasonably close but still not there – triathlon is so much more complicated than a single sport. And as you get to longer distances things like nutrition and wildcards like muscle cramping start to be more of a factor...these are things that are hard to train for. I imagine ultra-running has a lot of those issues at well. In any case there's a good chance I'll bite off an Ironman in my age-up year (2015) since selling that idea on the homefront is easier if I can pitch it as a 40th b-day thing. I've already laid the groundwork for this but nothing is guaranteed!!! In the meantime I'm already thinking about what the new challenges will be for 2014…for another discussion in a month or two…
The medical experts can fill us in here, but I believe HR is a very, very individual thing. I know it is related to age and capacity for a high HR goes down with age, but all the cookie-cutter formulas (e.g. 220-age for max HR) are unreliable. Mid 160's for me is actually quite low and I consider it sustainable for a very long time. A hard run workout for me will average 170's and a lot of it will be mid-to-high 170's. That's why I was pretty surprised I didn't drift higher throughout the run and why I felt I had so much aerobic capacity. When I do mile repeats and other LT/z4 training for running I'm usually in mid-180's and 187/188 is a typical high for my last couple of intervals. I don't usually get to 190 but it happens occasionally on a hot day.
I believe a lot of this is genetic. A training buddy of mine is 29 years old (I'm 38) and we run at pretty much the same speed and have very similar VDOTs. His HR for a really hard workout will be around 165. On the other hand, my dad who is just under 70 years old will see 180's when doing z4 workouts. I was talking to Matt Ancona once about this and was amazed to hear that his HR gets into the low 200's!!
Based on the above comment you can imagine my reaction to what you're trying to figure out is that yes, it is physiological. That is, unless you put a cap on your HR in training because of a perceived "limit". If the latter is true I suggest you don't train with HR at all, and just see where it falls. In practice I don't let HR govern my effort in workouts and in most cases don't monitor it in real time but rather look at the data ex post. Power and pace, baby!!!
Btw on the bike and in particular outdoors on the bike my HR is way lower…a z3/ABP ride is mid-to-low 140s, maybe drifting up to low-150s on a long ride.
My friend Rick would frequently get low 200s in his warm-ups! Crazy high!
I'm 55 and over the past 2 years I have run 3 marathons where my 3:35 (+/-) overall average HR was above what the generic formula predict as Max HR. My average HR for each of these races was between 166 and 169.
I also know that I can sustain 168 for about 3 hours then be able to go 172 - 174 for an additional 20 minutes as long as the Z4 HR comes during the second half. Spiking above 172 early will kill me at the end and will shorten the time spent around 167ish.
I see sparkles above 180 and it gets dark in the upper 180s. The highest I've pushed (several years ago) was 194 and that was excruciating to say the least.