Tuesday, April 23, 2013

A Nerd's Guide to Marathon Pacing

A Nerd's Guide to Marathon Pacing 8)

A post worthy of:

TL; DR

You do know what that means don't you?

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As race day gets closer, I start mulling over my pacing strategy for Tacoma. Recently Jill paid me this unexpected complement when I was asking for advice:


You are very consistent and know how to pace better than anyone I've ever met.

Having my ex-coach tell me that made me feel pretty darn good, let me tell you. Always good to have a coach that gives sincere complements 8) !

...and you know, I've had very good luck for quite a few races now (knock wood). So now I'm a expert. 

It wasn't always working for me: I've had plenty of 6 minute+ fades in my earlier marathons..oy I remember them... and my trail races are still poorly paced (even when it's two loops that are the same 8/) 

There is always more to figure out...

When you are a newbie (noob) you are still on the curve of huge improvement... which makes it less critical to nail pacing so precisely ....you might not go the fastest you could have gone but you could still set a PR. And that's just fine! Plenty more PRs that way 8)

But, those early PR harvesting sessions only last a few years. I'm not a noob anymore and my improvements are smaller...so I want every minute of performance!

Why such a big worry about the pacing? Because glycogen consumption goes up very VERY steeply as your effort level gets closer to your LT (lactate threshold). If you can keep the pace level very very even you will be able to push a few seconds per mile faster than somebody that varies the pace up and down a lot.

If you go too fast, even at a level pace, you are too close to LT and you risk hitting the wall later.

If too slow and you may not be able to make up the time you lost in the first part of the race. 

My preference is that a (flat) marathon pace should be no more than a minute or two off perfectly paced to be as fast as possible. How do we go about doing that?

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Here are some of the questions I go over (and over and over) before race day if you want to run your fastest..(I'm focused on the marathon here):

How good was the training buildup?

If you read my blog you know how closely I track my buildups.

With a number of buildups and race results behind you, you can compare the stats to each other and get a real idea of your relative fitness now vs then. Hubris and motivation are very important, but aren't enough..and even they too benefit from seeing cold, hard numbers.

I judge my cardio fitness by looking at average heart rate vs pace. There are a lot of ways to do this (checkout MAF testing) but you do need a HR monitor. I calculate something called YPB (yards moved per beat of heart) and track it for every single run I do. I don't need to do specific MAF tests because every run becomes a MAF test of sorts:  trends then become easier to spot. (If you live in a hilly area it is best to compare metrics for the same course)

Next there is fade resistance and LT threshold (and a bunch of other factors) for simplicity I'll just lump all this as "LT". 

This shows up as the HR rising gradually over the course of a long and/or fast run. As you get more fit, this 'cardiac drift' is reduced and you can see you are getting fitter. 

This one is important because if you look at your marathon HRs vs miles you'll see that in a long race your HR creeps up and when it gets up to 80-90% of your max HR you will be having to really push hard to maintain pace...you then enter the "gut-it-out" phase of the marathon.

The higher your LT is, the faster you can go (assuming your legs are ready for it) and not have your HR go up. It takes about 6 weeks to get some LT adaptation (by running tempo runs) and more is better (warning: too many threshold runs and you might burn yourself out or get injured before race day).

Cardiac drift also happens as you dehydrate during a long run (blood gets thicker), or as the temperature goes up (more blood volume to skin, not muscles) and that can confuse things but you can get a good idea if you have enough long runs how you are doing vs your previous buildup.

Then there are the legs: basic muscle mass and strength ..is it better? On this latest buildup I know it is because I can feel it...the muscles are actually bigger. Have you done more intervals? Hill running? Strength training (squats, single leg squats, etc)?

For there marathon there are the long run adaptations  Have you done your initial long run buildups at a slow enough pace? You can do parts of the  last one at full bore MP (in my opinion) but the earlier ones should stay slower than MP by 20-90s per mile. 

(The more long runs you've done in your life, I think the more you can push this. I've done 58 runs longer than 16 miles in since mid-2008. My feeling is that it takes longer to lose this adaptation than to get it. So, if you have run other marathons or kept up doing a long run every now and then in the 6-9 months you can push the pace more.)

There is also the bodyfat. Do you have more for this race or less?

Summary: 

Look at your training logs and get an idea where you stand.  You'll have a better idea what kind of pace you have in you. 

It also helps if you have a time trial or pre-marathon race to gauge your relative fitness with last time. In my case for my last three  buildups+races I did a HM 3-4 weeks before race day. 

There are many calculators that can tell you your Marathon pace given a HM result...they are not that accurate. Many of us run our marathons much slower than predicted.

But, more useful is knowing you did a time trial or race HM of X:XX and then ran a marathon of Y:YY. If you save 10s off of your HM pace you can then reasonably expect to take 10s off your marathon pace too.

How much do you want it?

This the second biggest component under my control. Do I really want a PR? What are my goals? 

In my case I am racing not only myself but father time. At 57 the average runner is slowing down a litte bit (about two minutes in the marathon) each year. So if you want PRs and not AGPRs (age graded PRs) you need to do them sooner rather than later. I might be "above average" and degrade slower, or you might be worse, but there are changes coming no matter what. 

I fully intend to set some AGPRs in the coming years  but meanwhile want a few more of the plain type 8)...And so do I have the  Steve Prefontaine-style GUTS it takes to hold pace in the last 6 miles and give it everything I have? 

The answer might be yes, for two reasons:

1) Once you are fitter, the wall becomes less harsh. With more leg strength, a good LT and solid long runs the wall becomes softer and more gradual. If you set the right pace you'll get to a mile or so of the finish before your run out of juice and then the closeness of the finish can give you just enough to hold for a few more minutes. 

I remember hitting the wall at SF in 2009 at mile 21 and just feeling completely at the mercy of it. Faded a minute per mile (and growing) and Nothing. I. Could. Do. I despaired as so many do. How to crack this thing?

What happened was I went too fast (although it didn't seem so at the time) and paid for it, hard. What I needed was strength training, intervals and tempo running.

2) Once you have gutted out a race finish a time or two you are more mentally prepared to do it again. But you need to want it and your fitness needs to be close enough to your target that gutting-it-out can work. You can't "gut-out" a pace that's total fantasy.


Course details and pre-race planning

I haven't crunched all the numbers but my recent pre-race HM shows I'm fitter than my previous buildups by about 10s per mile in the half. Sooo there's our buildup comparison then...what pace for Tacoma? 

To answer this question we have to take a bit of a look at the course. I am a firm believer in knowing what I'm in for BEFORE race day. If you actually have run the course in training or previous years even better! However, you can learn a lot by studying materials on the internet....

We need to see how much this course is going to speed us up or slow us down vs courses we compared our buildup with. AND we also need to have plan for the pacing variation during the course. 

The first thing I look at is the elevation profile:


That big valley that catches your eye is the Tacoma narrows bridge..the climb at kms 5 up to 8 is just after it. It's not quite as bad as looks. Here's the note on the website:

*Note on the Map My Run elevation profile going over the Narrows Bridge is not correct, the GPS drops below bridge level, the bridge deck elevation is approximately 187 feet in height. (57 meters)

But it is still going to be a long uphill grind..at least 1.5 miles at 3-4% grade or so..that mile will need to be way slower. How slow is somewhat a personal choice....I like to work the hills but not too hard, esp in the beginning. And I can see that there is a net downhill to the course that will let me make up some time...so I'm tempted to run uphill @MP+30-60s, maybe more.

Once I'm up on the long rolling plateau I plan to gradually get a little under pace and bank a couple of minutes for the other two medium hills ahead and the endgame. The endgame (last 6 miles/10km) is fairly flat but there are some rises and I might probably won't be able to hold pace perfectly on them....so a just a wee bit of banking, done very gradually, is in order for the endgame.

So to sum up: from 0 to 32 km (18 miles) I will have to bank about 120 seconds (which is about 7s/mile) except for when I'm on the 3 big uphills in that section. 

We all know how small the bumps can look on the maps and how @#$%?! big they look when you actually get there! One way to get a better idea about the hills is to use google street view to get in there on the course and look around. It's not perfect as it is hard to see small slopes but you can at least get an idea if there's a obvious gut-buster lurking. (UPDATE: this didn't work as well as I would have hoped...see below)

In the San Francisco marathon there's a nasty little 70' bump-up at mile 22-23 and if you don't know it's coming it can really throw your head game for a loop (ask me how I know ;)  I feel the more information the BETTER. Be prepared for race day and it will seem easier!

Update: I ran Tacoma and the profile was much hillier than the data would have suggested. In fact in order to help other people find real, garmin sampled elevation profiles I have posted a bunch of my race profiles here with other notes. I hope they help!

Next, we look at the course map  itself. This course has a lot of twists and turns which will require careful attention to the tangents. 

How well can we run the tangents? I am pretty good at that, but only if the course is not crowded can you really do it well. This race is not that crowded for marathoners: last year there were only about 450 people and at my pace only 120 ahead of me. Sweet! 

The snakey bits come mostly after mile 5, by which time we should be spread out. They are also mostly before mile 19 ...don't want to be worried about tangents and doing 90 degree or even 180 degree turns  when in the gut-it-out phase...it's a lot harder then! 

(In late stages of the marathon, you are stiff and sore and your muscles are willing to only do one thing..keep running as you've been doing. Asking them to do a 180 turn...OUCH, UGH, oOOOFF!)

You get the idea of the what runs through my head. My general feel is that this course is no worse than Eugene.. probably pretty close.

Race day conditions

Nothing you can do about this... but Tacoma was chosen partly because it usually has cool, cloudy weather at the beginning of May. 

The biggest enemy is hot temps. There is NOTHING YOU CAN DO if it's hot. You MUST slow down. Boston last year showed us that and the people that went out at a cold day pace suffered horrible slow downs and some ended up in the medical tent (which I think is stupid and dangerous, esp if you are on the older side)

The slow down with heat is not pretty. And those of us not acclimated  can do even worse. So let's not even bother to discuss this.

Tacoma has a 7am race start, which is a good thing as I'll be done by 11am and the temps should be cool. Marathons that start at 8am or even 9am are a not good unless it's  a really cold day.

For me (and most people) I think 60F is the limit..above that you will slow down. I prefer actually a bit colder, especially if it's sunny on the course. Full California sun on your bare skin is about equivalent to 10F in ambient temps. Shade is good (e.g. CIM has big shade trees during the last miles). Tacoma has some nice shade trees in the park on top of the plateau (seen in streetview).

Making it happen on race day

I have a pretty exacting technique here that I have evolved, it's not perfect but it works for me and it's for eeking out every last second.

The most basic thing you need to learn is how to tell your real pace from your Garmin average pace. As we all know, typically your Garmin pace reads better than your 'real pace' . You've all *heard* it:  you approach the mile markers and hear all the GPSes around you chirping before the marker. 

How *much* before the marker is the interesting bit.  I wear a pace band and I note the time as I hit the mile marker. Then, I see where I sit vs my real goal pace and calculate how many seconds per mile my real pace is off of my GPS average pace. This number is usually between 3-5 seconds. 

It is due to two things: 

1) Not running tangents, or even worse randomly jinking around down the course to avoid people, i..e you are running long...this is BAD.

2) GPS sampling errors. The computer in your watch gets a bunch of points over time and draws some kind of a line through them. The watch thinks the line is a good average fit. 

The points are not perfect at following your track: there is noise and there is also a problem if you are actually running a course that curves around a lot...the points may be far enough apart that it thinks you are going faster (e.g. switchbacks on a trail course). 

If your GPS watch has a 1 second sample mode, this can help with #2 but it's not really required.

Anyway, the details aren't too important but you DO need to keep track of the errors and figure out what to add to your GPS pace.

I use a pace band from here and my Garmin 610 watch shows me the following:

Time
Distance
Average Pace
ALP or Average Lap Pace (autolap interval set to 1 mile )

When I had a Garmin 405, I could only have 3 things and the first three I think are pretty standard for everybody. 

But I really really LOVE having the Average Lap Pace (ALP) for the current mile: it turns the race into 26 little races. I only have to hit my marks on each lap and the race is in the bag.

Here's how that works: 

Let's say my target Garmin pace is 8:45 for this lap because I need to bank a few seconds under my 8:50 Garmin target pace. My 610 just buzzed for the last mile and for the first few seconds the ALP is useless but after a minute or two it has enough data to get a better average and I can make very small adjustments in pace to keep it spot on my 8:45.

Let's say I hit a water stop in the first part of that lap and when I get to the half mile mark in the mile I'm then showing 8:55. It looks like i'm 10 seconds slow but remember this number as average is pace, not a lap split...I'm really only 5 seconds down since I'm only halfway through a mile...(i.e. it's telling me if I don't do anything I'll finish up the lap at that pace)

I look ahead in the crowd to a person roughly about 5 seconds ahead and very gradually make my way to that point over the next minute or two. 

I get early feedback when I'm slow or fast and I find this valuable. For example, sometimes in a race you get boxed in and tend to run at the pace of those around you. 

The ALP lets you know right away when this is happening. If you only have the Average and you are at mile 20, you can lose 20 seconds before the average shows you dropped a  second per mile.

As the race progresses is where this really shines. In the gut-it-out phase of the race the watch lets you know right away when your pace is off...gradually the effort level you feel goes up and the watch keeps you on pace. 

Without the ALP you don't have quick enough feedback when you are off or back on pace. It can be is demoralizing when your average drops below your goal!  You are working and working to bring it back down but don't seem to be having any effect (because the average has so many miles in it already it takes a long time to bring it back).

With the ALP method you totally focus on the current mile, win that and on to the next...it helps keep you from falling behind. It's really good for my morale to know I'm spot on.

At Eugene, I had about 60s of reserve, was in the gut-it-out last 6 miles, and could see on each mile I was losing about 10s. I could see my reserve eating up and I worked so VERY hard to keep the loss to a minimum. In the end I ran 6 seconds under my 3:55 and only by seeing that feedback and push each and every mile by itself could I make it happen. 

(My garmin actaully said 3:54:59 at the finish but I pushed the button late 8)

If I had a Garmin 405 I might wear a stopwatch on the other arm to free up one display item so that I could still have ALP showing.

So what's my Tacoma pace then?

Initially, I was thinking of targeting ~3:52 (8:51m/m)..but after my HM now I'm toying with targeting 8:48, (Eugene was 8:58m/m) or maybe even a stretch at 8:46 (a 3:50 marathon!)

This is a pretty huge difference in pace (12s mile) to be throwing around casually!

Even though my half marathon race was 10-12s mile faster than my HM time trial before Eugene.....erm... I'm not sure I'm ready to go that much faster for 26.2 miles.

I some of that HM speed was due it being an actual race situation and not a time trial. On the other hand a 1:48:30 half has taken many people to sub-3:50. 

The calculators, as usual, say I should be able to run much much faster in the marathon based on my half speed. ..and many have foundered as a result!

I will see how things go during the next two weeks / taper, (especially so with this tiny muscle strain in my right hamstring.)

 With 5s of GPS noise an 8:46 pace  I would probably will have to run 8:41 on the Garmin(!).....right now sitting in my armchair that seems damn fast...

Probably I will run to a 3:52 pace...and see how I feel at mile 16 or so.


















4 comments:

  1. You've definitely done your homework! I think you probably have a pretty good gauge of where you are what you can do. I'm hoping you can execute perfectly!

    Good luck!

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  2. +1 for ALP monitoring. It's even more fun in km, where you have 42 small 'races'. I barely even look at totals any more, it's easier to just keep track of how far ahead/behind of target pace I am.

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  3. Thanks for posting this, Paul. It's rich with very useful information and suggestions. With my first marathon just a few weeks away, I can clearly use it. Thanks for taking the time to pull it all together and post.

    ReplyDelete

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