Thursday, 24 April 2014

Good Day/Slow Day Highland Fling Splits

Running ultra marathons using splits is popular, with a range of approaches used, from using ones own splits from previous races on the route, using splits from training through to adopting average splits of previous races.  In this post I'll publish two sets of splits for the Highland Fling race, one set is are based on previous winner time and represent the splits that are likely to what we might achieve is we run the perfect race and finish strongly, while a second set is based on the average splits recorded during the 2013 race but as I believe most runners set out too fast and suffer in later stages using these splits for me represents when things don't go to plan and how you are likely to slow.

Winners splits are consistent year on year

The winner splits I am using are Andrew James's 2011 winning performance of 7:12 where he set the course record.  This course record was broken Lee Kemp last year (2013) where he lowered the record to an astonishing 7:02:50.  However, the route was altered last year due to path upgrading near Drymen, and Lee made a navigation error on route to Rowardennan which lost him time using his splits aren't likely to be as representative of a perfectly run race on the normal route, so I stepped back to Andrew' performance as my gold standard of splits.  

My confidence in these winning splits being pretty near optimal is based on analysis of previous years winners and course records, where there the difference between male winner splits is less 2% from each other, while others in the top ten and behind on average moving increasingly away from how the winners have consistently paced their races.  The following graph shows previous winners in men's and women's category in relation to Andrew's splits.  

Curiously only the two fastest female winners Lucy Colquhoun and Emma Rocha come close to this type of pacing and their times are way out ahead of other female winners.  I suspect the smaller number of international class woman attending the Fling makes the races less competitive at the front end compared to the men's race that has consistently seen near course record race wins over a number of years.  With less competitive races it's possible for a winner to get the pacing wrong and struggle on the day but still able to win.  Tracy Dean's courageous win last year saw here nursing a injured calf through the majority of the race and time and splits consequently suffered but she was still able to pull out a win. In the men's race it's been so competitive that a small slip up in racing will see them overtaken.

The key take home is that winners pace more consistently and evenly than the almost the whole of the rest of the field, the start at an relatively easy pace for them and finish strong while everyone else around them falters.  The "almost" the whole of the rest of field needs to be qualified, when you analysis all splits there are runners further back in the field that pace evenly as well, and my experience with using a HR monitor to guide pace has resulted in pacing that is far closer to winners splits than the average.  

Runners should take encouragement from this, while most go out too fast and suffer as consequence, it is possible to run your own race well, starting off easy enough that you can keep the stress on your body lower enough for spare glycogen stores, avoid early muscle damage and enable the body to keep digesting food and water.  If you start off easy then there is much greater chance of finishing strong, with the bonus of the experience being a positive one where one enjoys the race rather battling through from early in the race.

How to use splits when planning your own race

Knowing just how easy you should start off is difficult, first you need to know what time you feel can likely achieve on the day, then from this you can select the splits to match this time.  As there is no way we can know exactly how well the race will go on the day I believe it's best to not to try and pick on single target time.  

Instead I would advocate thinking about what your perfect race would turn out like and what time you might achieve if everything went to plan and you raced the perfect splits and the best of your ability, this is your time would define your "Good day" target time and the splits to select from this would be from the Winners splits, where you start steady and finish strong.

Not all races go to plan, it could be that we over estimate our fitness and choose splits way beyond our capability and go out too fast and then struggle, it could be that we get cramp or gastric stress that slows us down, or injure ourselves and then struggle for the rest of the day.  Choosing splits that account for this possible slow down provides us with a fallback set of splits to allow us to estimate our finishing time - these would be result in our "Slow day" target time and associated splits where we start a too strongly for our capabilities on the and finish slow.

If you choose your splits well then it's likely you'll be in between your "Good day" and "Slow day" splits, the nearer you are to your "Good day" splits the better your judged the day and paced the race. What will be apparent from the splits I present below is that the "Good day" and "Slow day" splits start close together near the start and steadily the "Slow day" splits drop off the pace and result in a much slower finishing time.  

For instance if I set off with with 1:50 split to Drymen (9:04 min/mile pace) then the "Good day" splits would see me finish in a time of 9:29:51, while the "Slow day" splits for a 1:50 initial split would see me finish in 11:13:21. If had chosen to use the "Slow day" splits for a finishing time of 9:30 we would have to do the Drymen split in 1:33 which is blistering 7:41 min/mile pace.  Such a strategy is likely to ruin our chances of succeeding on hitting our target time as even the "Slow day" splits would likely become impossible to sustain as we'd be burnt out by the time we reach Balmaha.  

Follow are the splits for the various legs and based on different times for the initial leg to Drymen, note the splits for sub 7 hours course record starts at 1:21, just a shade faster than last year.  The "Good day" splits are based on Andrew James 2011 race, while the "Slow day" is based on the average splits from the 2013 race.  I could label this as "Average day" but I don't believe average splits are best to aim at, instead we should aim for a perfect race, and if things don't go to plan we know we'll still finish in perfectly decent time. An important takeway is that for the perfect race you don't need to start fast to get a great time.



 Leg ratio Completed Leg distance Leg ratio Completed Leg distance Leg ratio Completed Leg distance Leg ratio Completed Leg distance
Winner 0.1930345572 12.13 12.13 0.2703255168 27.09 14.96 0.3003702561 41.04 13.95 0.2362696699 52.87 11.83
Average 0.1633621928 12.13 12.13 0.2641205352 27.09 14.96 0.3171045563 41.04 13.95 0.2554127157 52.87 11.83



























Drymen Leg Pace Rowardenan Leg Time Leg Benglais Leg Pace Tyndrym Leg Pace


























Good day 01:20:00 01:20:00 06:36 03:12:02 01:52:02 07:29 05:16:31 02:04:29 08:55 06:54:26 01:37:55 08:17
Slow day 01:20:00 01:20:00 06:36 03:29:21 02:09:21 08:39 06:04:38 02:35:17 11:08 08:09:43 02:05:05 10:34













Good day 01:21:00 01:21:00 06:41 03:14:26 01:53:26 07:35 05:20:28 02:06:02 09:02 06:59:37 01:39:09 08:23
Slow day 01:21:00 01:21:00 06:41 03:31:58 02:10:58 08:45 06:09:11 02:37:14 11:16 08:15:50 02:06:38 10:42













Good day 01:25:00 01:25:00 07:00 03:24:02 01:59:02 07:57 05:36:18 02:12:16 09:29 07:20:20 01:44:02 08:48
Slow day 01:25:00 01:25:00 07:00 03:42:26 02:17:26 09:11 06:27:25 02:45:00 11:50 08:40:19 02:12:54 11:14













Good day 01:30:00 01:30:00 07:25 03:36:02 02:06:02 08:25 05:56:05 02:20:03 10:02 07:46:14 01:50:09 09:19
Slow day 01:30:00 01:30:00 07:25 03:55:31 02:25:31 09:44 06:50:13 02:54:42 12:31 09:10:55 02:20:43 11:54













Good day 01:35:00 01:35:00 07:50 03:48:02 02:13:02 08:54 06:15:52 02:27:49 10:36 08:12:08 01:56:17 09:50
Slow day 01:35:00 01:35:00 07:50 04:08:36 02:33:36 10:16 07:13:00 03:04:24 13:13 09:41:32 02:28:32 12:33













Good day 01:40:00 01:40:00 08:15 04:00:02 02:20:02 09:22 06:35:39 02:35:36 11:09 08:38:03 02:02:24 10:21
Slow day 01:40:00 01:40:00 08:15 04:21:41 02:41:41 10:48 07:35:47 03:14:07 13:55 10:12:08 02:36:21 13:13













Good day 01:45:00 01:45:00 08:39 04:12:03 02:27:03 09:50 06:55:26 02:43:23 11:43 09:03:57 02:08:31 10:52
Slow day 01:45:00 01:45:00 08:39 04:34:46 02:49:46 11:21 07:58:35 03:23:49 14:37 10:42:45 02:44:10 13:53













Good day 01:50:00 01:50:00 09:04 04:24:03 02:34:03 10:18 07:15:13 02:51:10 12:16 09:29:51 02:14:38 11:23
Slow day 01:50:00 01:50:00 09:04 04:47:51 02:57:51 11:53 08:21:22 03:33:31 15:18 11:13:21 02:51:59 14:32













Good day 01:55:00 01:55:00 09:29 04:36:03 02:41:03 10:46 07:34:59 02:58:57 12:50 09:55:45 02:20:45 11:54
Slow day 01:55:00 01:55:00 09:29 05:00:56 03:05:56 12:26 08:44:09 03:43:14 16:00 11:43:57 02:59:48 15:12













Good day 02:00:00 02:00:00 09:54 04:48:03 02:48:03 11:14 07:54:46 03:06:44 13:23 10:21:39 02:26:53 12:25
Slow day 02:00:00 02:00:00 09:54 05:14:01 03:14:01 12:58 09:06:57 03:52:56 16:42 12:14:34 03:07:37 15:52













Good day 02:05:00 02:05:00 10:18 05:00:03 02:55:03 11:42 08:14:33 03:14:30 13:57 10:47:33 02:33:00 12:56
Slow day 02:05:00 02:05:00 10:18 05:27:06 03:22:06 13:31 09:29:44 04:02:38 17:24 12:45:10 03:15:26 16:31













Good day 02:10:00 02:10:00 10:43 05:12:03 03:02:03 12:10 08:34:20 03:22:17 14:30 11:13:27 02:39:07 13:27
Slow day 02:10:00 02:10:00 10:43 05:40:11 03:30:11 14:03 09:52:32 04:12:21 18:05 13:15:47 03:23:15 17:11













Good day 02:15:00 02:15:00 11:08 05:24:03 03:09:03 12:38 08:54:07 03:30:04 15:04 11:39:21 02:45:14 13:58
Slow day 02:15:00 02:15:00 11:08 05:53:16 03:38:16 14:35 10:15:19 04:22:03 18:47 13:46:23 03:31:04 17:51













Good day 02:20:00 02:20:00 11:32 05:36:03 03:16:03 13:06 09:13:54 03:37:51 15:37 12:05:16 02:51:21 14:29
Slow day 02:20:00 02:20:00 11:32 06:06:21 03:46:21 15:08 10:38:06 04:31:45 19:29 14:16:59 03:38:53 18:30













Good day 02:25:00 02:25:00 11:57 05:48:03 03:23:03 13:34 09:33:41 03:45:38 16:10 12:31:10 02:57:29 15:00
Slow day 02:25:00 02:25:00 11:57 06:19:26 03:54:26 15:40 11:00:54 04:41:28 20:11 14:47:36 03:46:42 19:10

For myself my own targets for this years race (this Saturday) are:

Platinum : 9:30hrs, unlikely but if everything went perfectly and raced above expectations

Gold: 10:00hrs , a more realistic goo day target, I would love to get a sub 10 hours, even if just be few seconds

Silver: 10:20hrs, I think as long as I don't mess things up it should be possible.

Bronze: 10:46hrs, to match match my Highland Fling time of 2012 where I had a good day, but I'd honestly be a bit disappointed if two years on and all my good ultras in Autumn of 2013 that I wouldn't be faster.  Ultra's can be cruel though, you just don't know what's going to happen on the day.

This leaves me looking at a 1:50 to Drymen for me to get within range of my very lofty target of 9:30 hr time, to go out slower than this will likely start reducing my chances of achieving it.  If this was too fast then my chances of doing my more realistic target of 10 hours will be reduced too.  A conservative start would see me look at 1:55 initial which would make a sub 10 hour time more achievable.  

The low risk, lower reward approach would be to head out at ten minute mile pace and arrive at Drymen at around the 2 hour mark.  In my 2012 race I arrived at Drymen in 1:58 and went on to finish in 10:46, but I struggled with low energy levels in the last three miles and had to walk far more of the final miles than I was happy with.  If I am indeed fitter and in particular better fat burner as I suspect I am then I should be more capable of keeping the pace up right through to the end, so even with a slower start I could still realistically be thinking about my silver target of 10:20. 

Based on the "Good day" splits I know that I'd be crazy to start out faster than 9 min/mile pace as it'll likely be unsustainable. If I do end up going through Drymen in a sub 1:50 time I'll know that I need to back off and start conserving my energy better.  If I go through Drymen between 1:50 and 1:55 I know that I'm being competitive but not necessarily fool hardy if it is to be my day and I can manage to stick close to the "Good day" splits through to the finish.

Pacing by Heart Rate

In my recent post How to pace the perfect marathon or ultra marathon I advocated pacing using a Heat Rate Monitor, which will probably lead one to question this post, which one is best?  Race by splits or race by Heart Rate?  If the later what what heart rate to use?

My plan this Saturday is pacing primarily using my Heart Rate monitor with "Good day" splits as a secondary guide to whether I might be over cooking it and also to help project what time I might be on for. If I am able to stay with a heart rate in my target zone for a section and within range of "Good day" split will be reassuring, if I'm too slow or too fast then I will have a bit of feedback on just how well my body is coping on the day - if my HR is high for a given pace then I'll know to be more cautious, but if it's lower then I could be my day I have the headroom to chase a fast time and more optimistic splits.
Finally knowing that I might still be on for a sub 10 hours time could be quite motivating in the last section from Beinglas to Tyndrum.   

The advantage that pacing by Heat Rate has is that helps you even out all the ascents/descents and changes in terrain/weather so you avoid pushing on too hard on ascent, or taking it too easy on a descent.  Running across hilly terrain makes following average pace splits next to impossible, by contrast pacing by HR needs no mental arithmetic, just a quick glance down to the HR monitor watch to check that I'm within a target zone.

Pacing by HR can also be tweaked to fit with average target pace, if you are slightly too fast adjust the target HR down, if you are a bit slow adjust it up.  

In my 2012 Highland Fling race my HR monitor recorded an average HR of 152, in my 2013 Devil O'Highland Race my average HR was 154 (it's a shorter race so higher intensity).  I expect if my race goes to well then I'd see a HR around that of my 2012 Highland Fling race and may actually be a little lower as I'm two years older (max HR goes down with age), and hopefully fitter thanks to my West Highland Way race training,

Based on an assumption of an average HR of 152 by plan is to account for HR drift through the race, breaking the race into three sections:
  1. Milnagaive to Drymen, start first few miles at a target HR of 140, but keep below 150 to Dyrmen
  2. Drymen to Beinglas, the central 6 hours of racing I'll target 150 to 155, with a hard limit of 160 being a Heart Rate to NEVER exceed.  I have found when I exceed 160 in ultra's cramp and/or gastric stress have often been close behind.
  3. Getting to Beinglas in good shape is my key objective, running conservatively be holding myself back  to not got faster than the "Good day" splits and keeping the HR sensible should ensure that my body is able to conserve glycogen stores, avoid overheating and associated fluid loss, and keep my digestion ticking along nicely.  
  4. Once I get to Benglas I'll asses how my body is responding and look to race the last 12 miles to the best of my ability, splits will be out of the window, and I'll relax my target HR allowing it to go higher if my body is able.  If I've got cramp, suffering with gastric stress, muscle fatigue etc. then I'll keep the HR target range conservative.  If my body can handle increasing the effort level then I'll happily let it go up to around 160, and in the last few miles even that limit I'll happily ignore if my body is responding well.
If you are thinking about using HR monitor for pacing as well then using previous average HR for a previous race of similar race is good place to start.  If you don't have this then aiming for around 25bpm lower than the HR you'd see at lactate threshold or average 10k racing HR would also likely be a reasonable target.  For reference by 10k race HR averages around 178, while my max HR is around 190.

Best of luck with race if you are racing and see you there. In case your wondering what I'll look like come race day, here's a photo from last years very wet Devil O'Highlands Race.  Sadly the forecast isn't that great so I suspect my Montane running jacket, worn below, will see plenty of action again.


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Wednesday, 23 April 2014

What slows us down, Part 2

In my previous post "What slows us down, Part 1" I dived into the topic of why it's hard to maintain pace when running long races, it's a big topic though, so only covered the topics:
  1. Conscious and sub-conscious, the role of Central Governor
  2. Homoeostasis
  3. Liver and Muscle glycogen depletion
In this post I'll cover just Fat vs Glycogen/Glucose metabolism

4. Fat vs Glycogen/Glucose metabolism

Our muscles and various organs primarily use fat and glucose/glycogen to power the function. When glucose is stored in muscles and the liver it's stored in a slightly altered form called Glycogen.  Our muscles will use the local glycogen preferentially while stocks are still high, but as glycogen stores diminish our muscles have to turn increasingly to metabolising fat or source glucose from blood glucose.

When our muscles work hard they almost exclusively use glycogen as fuel and at the highest intensities burn the glycogen anaerobically (without oxygen) which is great for a quick burst of power but very only uses 1/18th of the energy available in glucose, one of the bi-products of this crude but quick process is lactate which contains the remainder of chemical energy and hydrogen irons that lowers our muscle Ph making it more stressful environment for metabolism and fibre integrate.  A small amount of anaerobic metabolism generates a great deal of lactate so even when running at marathon pace where about 1% of power comes from anaerobic metabolism we could envisage nearly 20% of available fuel at marathon pace being in form of lactate.

Our muscles also can use lactate as fuel through a process called the Cori cycle, this process isn't 100% efficient though, and lactate can only be metabolized using aerobic pathways, so it's only our slow twitch or aerobic fast twitch fibres that will be able to utilize it.  For an ultra runner we should be running more aerobically than a marathoner so the fuel mix will see much less lactate, it will still be there, especially if you push on too hard up a hill.  If you feel the burn going uphill during an ultra it's a strong sign that you are working too hard and should ease off immeditately.

Our brains and gut have a strong preference for using glucose so when glycogen stores are getting low our bodies increasingly reserve the remaining glycogen stocks in our liver for use by the brain. The body uses the hormone Cortisol to signal for the liver to release glycogen and at the same time signal for the muscles to take up less blood sugar.  This is very clever adaptation for survival but it does mean that the longer we run, the more our liver gets depleted the higher cortisol will be, so that our muscles take second dibs on any sugar we consume during the race.   Therefore avoiding high cortisol levels may be crucial factor in making sure that we fuel both our brains, gut and muscles with the food we eat.

A big part in avoiding depletion of glycogen stores in our liver and muscles is how efficiently our muscles can metabolize fat.  Our diet, training and genetic make up all have a role to play in just how much we metabolize fat at different intensities, the following two charts plot how much fat and carbs (glucose/glycogen) that our complete bodies use a different intensities (HR along the horizontal axis, Calories per/hour vertical axis).  The first chart is from data collected when Scottish Ultra runner Caroline McKay was tested in here run up to the Highland Fling in 2013, the second is for a publish paper that looked at well trained athletes.

Fat/Cab metabolism for Ultra runner Caroline McKay
Far/Carb metabolism for well trained athletes.
The differences are startling - Caroline is able to use 70% fat, 30% carbs at intensities we run Ultramarathons at, while the conventionally training athletes came it at around 30% fat, 70% fats.  One of the likely keys to this difference is that Caroline was following a broadly low carb Paelo diet at the time of the tests.  Here ultra marathon focused training will also be a factor, but likely less significant than the diet.

Genetics will also play a role - we all have different mixes of slow and fast twitch fibres, those with more slow twitch have a higher capacity for aerobic metabolism and as fat can only be processed aerobically it puts a strong bias towards in favour of slow twitch dominated athletes.   Also on average females have more slow twitch fibres than males.

Results for ketogenic (very low carb diet) athletes have shown even higher utilization of fats, however, ketogenic athletes have yet to show benefits in races performances, while there a numerous cases of ultra-runners adopting lower carb diets and seeing good improvements to their ultra-running.  Very little research has been done in this area so it's not yet possible to say what level of carb/fat/protien mix be idea, and it's likely to be different from individual to individual.  I suspect through the 80's, 90's and 00's we were consuming too much carbs to be healthy let alone perform to our best in ultra marathons so going back to times before heavily processed food and large amounts of high GI carbs will likely help most runners.

I count myself as just one example of a ultra-runner that has seen improvements with going from a typical western high carb diet (I'd guess roughly 60% carb, 25% fat, 15% protien) to lower carb diet (~35% carb, 50% fat, 15% protein).

Come race day you can't massively alter how much fat your can metabolize, but what you eat and when can alter things a little.  Eating a high Glycemic Index (GI), high carb meals in the days and hours prior to race will push up blood insulin and shift the body to storing blood sugar as glycogen and fat rather and switch off burning of fat.  To avoid this insulin spike you need to take care when carbo loading prior to race, make sure it's of low GI type, and consumed with protein and fat to slow digestion and lower the GI.

During a race our muscle and liver become more sensitive to insulin so that little is required for our bodies to take up and manage blood sugar without risking a big insulin spike and shutting off fat metabolism.  You should be able to eat higher GI foods when doing your ultras, but you'll still need to take care because of gastric stress, big intakes of sugary liquids and solid foods are still likely to cause problem just of different types.  I'll touch on this topic in a later item.  In general I'd suggest consuming a modest amount of easy to digest carbs continuously through a race, consuming as little as 100 carb calories/hour will probably work fine for most runners, especially those able to burn fats efficiently.  

I find it useful to think about fuelling the liver and brain to keep them happy, rather than attempting to fuel the muscles on sugars as you simply can't keep up with their needs - muscles should burn primarily fats during ultras and we should do everything we can to help them do this.

 Another big factor we have control of during the race is our pacing, if you look at the graphs the amount of fats metabolized drops off very rapidly as intensity increases.  The rate of drop off is also much more severe for athletes that can't metabolize fats well so it's a double whammy.  For these sugar dependant athletes it's become far more critical to avoid spikes in intensity, while for fat burners they will likely be able to accommodate an occasional pacing error with less detrimental effect.

For the sugar dependent types pacing as evenly as possible is critical, for this I'd recommend considering racing by heart rate (HR) as I discussed in my recent blog entry  "How to pace a perfect Marathon or Ultramarathon" http://trossachstrailrunner.blogspot.co.uk/2014/04/how-to-pacing-perfect-marathon-or-ultra.html.  Racing by HR will also help fat burners but they can probably be bit less strict on just how even they pace.

Another approach with pacing is to use the splits percentages that the winners of ultra races use rather than the average splits from all runners in a race as is typically done.  From my analysis of Devil O'Highland and Highland Fling Ultra the winners almost always demonstrate the most evenly paced race in the whole field.  Following what the best do on their best days is likely to be much more efficient than pacing to what the masses on average do.  A few of the "masses" run perfectly paced races like the winners do, but the vast majority go out way too fast and suffer in the later stages. Glycogen depletion associated with these fast starts is key factor why they suffer.

I have a post "Good day, Bad day splits" in the works for the Fling, so I'll wrap up now and try to get on to posting this tomorrow - only three sleeps till race day now :-)

Thanks for reading.

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Tuesday, 15 April 2014

What slows us down, Part 1

Running Marathons and especially Ultra-Marathon tax out mind and bodies in quite different ways to shorter races, the further you run the less important basic speed is and more important mastering all the other aspects of what effects our running performance.  In a series of posts I'll explore what I've learnt so far about effects our running performance during very long runs and provides some suggestions on what we can do to minimize what slows us down.

What slows us down

In this section I'll quickly enumerate various issues that we have to deal with as the race progress, then in the next section start to look at these in more detail with suggestions on what to do in training and on race day to mitigate how much they'll slow us down.
  1. Conscious and sub-conscious, the role of Central Governor
  2. Homoeostasis
  3. Liver and Muscle glycogen depletion
  4. Fat vs Glycogen/Glucose metabolism
  5. Muscle damage
  6. Injury
  7. Central Nervous System (CNS) Fatigue, and in particular Cramp
  8. Blood imbalances and toxicity
  9. Hormones
  10. Mental Fatigue and Mental State
  11. Heat Stress
  12. Cold Stress
  13. Gastric Stress
  14. Dehydration
  15. Blood pressure
  16. Navigation errors
  17. Terrain
  18. Weather
  19. Night vs Day and the need for sleep.
  20. Pacing + splits
In this Part 1 post, I'll discuss my thoughts on points 1 through to 3, and tackle the others in subsequent posts.  

Disclaimer, I'm not a medical expert so feel free to correct me/add to my own thoughts - it'd be great to spark debate on these topics.  What I write here is is all stuff I've gleaned from books/articles on the web, drawing all this stuff together in the context of marathoning/ultra-marathon hasn't often been done so I think it should make for an interesting discussion - even if it takes a bit of geek to really enjoy this type of pondering! :-)


1. Conscious, sub-conscious and the role of Central Governor

Our brains work at both conscious and sub-conscious levels as we run our races, both sides are entwined together in ways that aren't readily apparent to the conscious thought that we relate to as being the person we are.   Ideas spring up into our conscious thought seemingly randomly, but often it'll be something that one of the sub-conscious activities of our brain need to raise up for us to deal with consciously, be it realising we are thirsty or need the loo through to becoming aware of fatigue or injury.  Understanding that this interplay is at work is crucial to how all our systems mesh together. 

Our sub-conscious brain activities can be quite autonomous and reach down into our central nervous system and down into our gut that itself has a very sophisticated nervous system.  These sub-conscious systems run our body and make sure that our hearts beat, our lungs function, management of  digestion works, heating/cooling of our bodies 

One aspect of this sub-consciousness processing has been labelled in Sport Science as the Central Governor.  The Central Governor is more of emergent behaviour rather than a specific bit of processing or part of brain, it's a likely a collection of different safety mechanisms built into our brains/central nervous system that work to ensure that we will survive whatever endeavour we are pushing our bodies through.

Our conscious thought sits above all these sub-conscious systems and can hint to them that we wish to go faster, but it can only hint, if these systems don't feel it's safe then can be quite unresponsive and reply to us with pain the fatigue.  The is now even speculation that fatigue itself could be an emotion conjured up by our sub-conscious to slow us down.  I believe it's likely that we feel like we've hit "the wall" when running it is likely to be our Central Governor deciding that we don't have a safe reserve of fuel or hydration to push on and passes this message on as fatigue.  This fatigue can be all consuming, where no amount of conscious will can coax us back into swift motion.  This fatigue can also be ephemeral, even small bits of new external or internal information can be enough for the Central Governor to relax it's grip and our pit of fatigue can lift.  

Figuring our what our Central Governor is concerned about can be key to avoid these low points and helping get of them if we find ourselves struggling.  The further and longer your run the more likely you'll hit these low points.  As the Central Governor watches over all our bodies systems, most of the points I raised above are under it's umbrella, all of these elements can individually slow us down, but it's the Central Governor's role to integrate all of this and provide feedback to the brain about overall health status.

It's not often to hear athlete's talk about mind of matter, that from some where  deep they found the will and energy to carry on.  Personally I believe this shouldn't be a battle of conscious will against the Central Governor.  We shouldn't try to beat it into sub-mission but work with it, listen to what it's telling us even if how it tells us can be a bit indirect, if we fix the problems then it will relax it's grip and we can progress.  

In terms of finding energy from nowhere, this isn't really the case, we have the energy systems within to live for months without food for months before death, all we really are doing when we find these hidden reserves is to metabolize fats and proteins for energy, or empty our liver glycogen stores just a bit further than our Central Governor previously thought safe for us to utilize.  Our bodies are perfectly capable of functioning with low reserves, and if you have trained to use your fat reserves efficiently you can actually move efficiently for many hours.

The better we get at listening to our bodies needs and the sooner we address them the happier our Central Governor will be and the less it'll stand in our way and better we can perform.  The better you get at this the less conscious effort will be required to overcome fatigue and the faster you'll be and the more you'll enjoy your races.

It has been found that the Central Governor includes an ability of it to be predict what will happen to our bodies in the future, so if the day is going to be hot then it can slow us before we generate too much heat of our own.  Central Governor also can be trained so that if your are safely pushed your body before it's far more likely to stay relaxed and allow you to push further and harder.

Conversely if something unexpected happens the Central Governor have rapidly become conservative and hold you back.  If you can avoid sudden and unexpected external changes then Central Governor will itself be able to better predict what will happen next and if it's safe then to stay relaxed and not interfere.

2. Homeostasis

While the Central Governor concept provides a umbrella model of the sub-conscious processes that watch over our body and it's physical output (i.e. our pace), the concept of Homeostasis is a companion concept of collection of physical systems in the body that need to be maintained internal balance with various systems kept with in safe limits for us to remain healthy and fully functional.  The further we push our bodies out of Homeostasis the greater stress, damage and ultimately life threatening risk.

The systems that our bodies attempt to keep in Homeostatis include:

  • Temperature
  • Water
  • pH
  • Blood sugar levels
  • Electrolyte balance
Our nervous and endocrine systems control homeostasis using feedback systems provided by various organs.  I also expect the Central Governor will also be part of the loop as management of these systems are directly effected by the intensity of exercise, so if the Central Governor steps in and slows us down by creating fatigue the pressure pushing us out of homoeostasis can be reduced.

At a conscious level we can also monitor what systems that need to be kept in Homeostatis and react to it or even better plan ahead so that we can alter what we do, wear, or consume to help our bodies remain in Homoeostasis.

3. Glycogen Depletion

Usually when runners think about Glycogen (the form of sugar stored in our muscles and liver) depletion we think of our muscles running our of Glycogen and this causing us to slow. While this is big factor for us to contend with it is far from the mos critical one in terms of the risks of Glycogen depletion as our muscles can turn to metabolising fat for fuel.  The more slow twitch fibres a muscle has the more capable it is of metabolising fat for fuel.

By contrasts the brain can not directly metabolize fat, it relies primarily on blood sugar for it's function.  If our blood sugar drops then our brain will begin to fail, early signs will be poor brain function, but if blood sugar goes lower we loose consciousness, and if lowers still further we will die.  The organ in our body that has the task of maintaining blood sugar is our liver that has stores of glycogen that it steadily releases into our blood stream as required.  If our liver becomes seriously depleted of glycogen it can turn to glycogenesis (converting protein to glucose) and ketosis -- converting fats into ketone bodies our brains can use in place of blood sugar.  However, these systems don't readily take up the slack.

Given the critical nature of blood sugar to our brains and how it's the liver that required to maintain blood sugar the level of glycogen depletion in the liver is crucial organ for the Central Governor to track.  If the Central Governor predicts that we are exhausting our liver glycogen stores then it will fatigue us to dramatically slow us down until the demands are low enough to be taken up by glycogensis and ketosis.  This slowing might mean walking right down to needing to lay down and sleep.

Another organ that is reliant upon blood sugar is our digestive system.  When blood sugar is low it's ability to digest food and water is impaired.  This may be a factor is why gastric stress can plague us during the second halves of ultra-marathons.

Given the reliance of our brains and gut function in blood sugar levels and their reliance upon the liver to maintaining it, avoiding liver glycogen depletion is likely more important to avoid than muscle glycogen depletion.  When we eat during an ultra-marathon consider foods that replenish the liver efficiently and maintaining blood sugar rather the viewing food as fuel as fuel for our muscles. 

Glucose gets absorbed via the small intestine into the blood stream, while Fructose (fruit sugar) and Lactose (milk sugar) get shunted directly to the liver.  We can't absorb as much Fructose and Lactose as Glucose so it doesn't make sense to just rely upon these pathways, instead the most productive route is likely to consume something like a 2:1:1 mix of Glucose, Fructose and Lactose.   

Glucose can be consumed in the form of complex carbohydrates rather than straight Glucose, the digestive system breaks down the complex carbohydrates down into Glucose which is then absorbed into the blood stream.  Carbohydrates takes longer to digest than Glucose so provide a steadier release into our blood streams so generally is likely to be preferable for longer races.

The Central Governor also watches what we eat and uses this into own predictions.  It has been found in study that even washing your mouth with sugary drink and then spitting it out can fool the Central Governor into thinking that glucose is safely on it's way and that it can release it's grip on our pace and we can feel a boost of energy.  This isn't something you'd want to do during the first part of long race, but near the end where gastric stress can be limiting what you can consume it can be a useful trick to coaxing your body over the line. 

--

In Part 2 I'll work through more items on my shopping list of what slows us down, I'll try to get to this over the next week.
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Thursday, 3 April 2014

How to pace the perfect Marathon or Ultra-marathon

In search of Optimal Marathon and Ultramarathon Pacing.

The general rule for pacing that is preached by the best coaches and sports scientists is an even split or slightly negative is optimal, and this is prescribed for elite's and every day runners, but is this advice sound?  I'm not one to take things on face value, but as an inquisitive sort I've thought about the topic extensively and tried out things in my own racing.  The more I've looked into the topic the more convinced I have become that this approach is sound.  This view is based on analysis of what elite's use, and also my understanding of physiological demands that the runner is placing themselves under.

Previously I wrote about elite marathon pacing is my post  2013-London-Marathon-Elite demonstrate folly of Positive Split.  Another great discussion about elite marathon pacing can be found the Science of Sport website, relevant articles : Wilson Kipsang’s marathon world record: Pacing and splits, Geoffrey Mutai: 2:04:15, misses WR, Haile Gebrselassie World Record 2007.  There is also a convenient thread for all their marathon analysis.  If you real all these bits of analysis it becomes clear optimum pacing for elites is even pacing, with big penalties paid for times when athletes surge or push on too hard at any one stage.

Another hint that even/negative pacing is provided in a quote from an Jez Brag in an interview published in Ultra Tales:

"Jez Bragg: From my experience the best way to find the ‘magic’ ultra running gears is to be patient, and start steadily. Even pacing, or ideally running negative splits, is the ideal approach to achieve this. By ‘magic’ gears I mean when you settle into a strong pace that feels effortless and like you can go on forever. It does happen; it is possible. That’s how the really special ultra running performances are achieved. The bottom line is that it’s very individual and it’s a case of finding out what works best for you."

Not only does Jez say even pacing is best, but this is exactly what he does - his course record on Devil O'Highlands is almost perfectly evenly paced. Last year I did some analysis Devil O'Highland splits, but alas been too rushed off my feet to write it, the short story of this analysis is Jez' course record stands out clearly as the strongest second half ever run on the route.  The pacing that female Devil O'Highlands record holder, Lucy Colquhoun, was also very close to even pacing.  This pattern is repeated in analysis I've done of the Highland Fling as well. Whether it's marathon world records or local ultra marathon records, the theme is consistent:

The best of the best run with very close to even pacing.

Muscle Fatigue and Muscle Damage

All marathoner will suffer fatigue and portion of this will be down to muscle damage.  Damaged muscles are less efficient so require more energy to generate the required forces, and also results in greater perceived effort level to maintain force output and pace.  Not only does this chime in with my own experience but studies have also shown how muscle damage accumulates through longer races, I guess it's one of items that is common sense and common experience.

I believe the amount of muscle damage and general muscle fatigue that we accumulate is directly related to pace that we have already run at for the preceding miles.  Running at 7:00 min/mile pace for 13 miles leaves the body with much greater muscle damage and glycogen depletion than running at 7:30 min/mile for 13 miles.  I do not believe the relationship to be linear, running 5% faster won't lead to 5% more muscle damage and glycogen depletion, but will lead to more than 5%.  Exactly how much I don't know, but I know for sure from my experience training and racing it's not linear, going a little bit faster can create a lot more damage.

In my articles from last year on the effect of fat vs glycogen utilization and  pacing strategies on glycogen utilization I touched upon the non-linear relationship between glycogen and intensity, one of the graphs that I included show how rapidly glycogen rises as intensity rises (this is based on study data of well trained athletes), I'll reproduce here so you can see how small increases in intensity have a big effect on how much fat and glycogen(carbs in the graph) you'll need:
My guess us that rate of glycogen depletion and muscle damage are correlated, although a causal link might not be direct.  The bottom line is the faster you run the faster you deplete glycogen and the faster your damage.  The fact that the relationship is non-liner it's likely we'll pay a dis-proportionate amount for going too fast over any particular section.  This is something that can been with the elite marathoners - an surge too early or too hard can blow a field apart and often kill the chances of the one pushing the surge.

Could a Positive split optimal?

Positive split has some advocates, even if they are far outnumbered by the those advocating event splits. In the British ultra-marathon scene Stuart Mills is one such advocate of positive splits with his "run as fast as your can for as far as your can" philosophy of pacing.  Could this approach be view be optimal?

A positive split strategy deliberately has the first run faster, but this does mean you are creating more more muscle damage and greater glycogen depletion in the first half of the race than an even or negative split strategy.  With more muscle damage you physically have to expend more energy per mile to cover the second half.  With greater glycogen depletion you also have to draw that greater energy contribution from your fat reserves, which in turn means greater oxygen load as well as greater perceived effort level to maintain pace.  Carrying a lower efficiency over the second half of the race will mean that the total energy requirement for a positive split will be greater than that of even or negative split.

Now Stuart's hypothesis is that in response to this muscle damage will enviably slow down and should plan for it.  Stuart's uses his own analysis of London marathon results that show the vast majority of runners including elites positive split, and my own analysis of ultra-marathon also support the observation most athletes positive split.  What Stuart then claims that this means positive split is optimal.  I can't figure out why he believes this to be sound conclusion.  To me it's akin to saying because on average the UK population is getting more overweight we should all therefore should aim to gain weight. To me all Stuart's analysis proves is that on average runners slow down in marathons, however, it simply isn't at all useful at telling us what is optimum - you have to use other types of analysis for this.

From a theoretical standpoint I can't see how running a positive split could be beneficial.  It requires more energy due to having to carry greater muscle damage through the second half of the race.  It requires you to run faster at the start of race before your body has fully warmed up and moved from anaerobic to aerobic metabolism wasting precious glycogen.  There is also a physiological price to pay - slowing down is demoralizing, as is being passed by runners who are looking stronger and fresher, you also have to carry yourself on fatigued legs that with every step eat into your soul and will to maintain the pace.  Going out fast and then hanging on is really tough mentally as well as physically.

Having followed Stuart's blog for a few years I do wonder if this last observation may be a key to understanding why he advocates a "Going out as fast as you can for as far as you can" - could it be this pacing approach makes you feel like you've run the absolute hardest and put in the most effort you could have at all points in the race.  It makes you feel that you put your all into all, you suffered for your performance so it must be the fastest you could have run.

This logic ignores the fact that such pacing causes greater muscle damage, dehydration and glycogen depletion and erodes your mental state, so while it might feel that you are running as fast as you can at any point in reality have to slow down more in the second half than you save in time by running fast in the first half.

Stuart's performance can be a bit hit and miss.  Some races he runs well and has won some huge races, but these all balanced with other races where things don't go right, or where it seems like after one third or half way he simply gives up racing completely.  Stuart often puts this less successful races down to lack of mental as much as physical preparation, but perhaps the pacing strategy is high risk and contributes to these days that don't go so well.  For these races that don't go well perhaps "Run as fast as your dare, or as far as you care" might be a more suitable signature.

I haven't yet seen a compelling argument why positive split might advantageous, and I've yet seen any good real world data to illustrate that it is appropriate for any one, let alone the average runner who is mostly likely to suffer serious muscle damage and fatigue from pushing pace early in long race.  I can't help feel a bit frustrated with Stuart.  He is massively talented runner that has so much potential, but for me I feel it rather squanders it on a less than rational pacing strategy.

What might be optimal pacing look like in practice?

So what should the runner do?  Even or slight negative split looks best from a theoretical standpoint (looking at muscle damage + glycogen depletion, heat stress and dehydration), and is backed by what pacing strategies that world top long distance athletes use when they run their best races.

In practice  one should run the first 15 minutes slower than your average pace to allow you muscles to warm up to temperature that it operates mostly efficiently at - start too fast an you are far more anaerobic and burn precious glycogen and increase muscle PH - which in turn leads to more fatigue and muscle damage.  Once past this easy start and your are fully warmed up you then steadily approach your average pace/intensity that you then aim to maintain for the majority of the race.  If the race has been run well then in the final miles it's then possible to pick up the pace a little and run a strong finish with what glycogen stores are remaining.

While I believe this to be an optimal strategy is hard to achieve and most runners aren't taught or practice pacing enough to do it.  Running the first few miles at slower than your target pace is especially hard as adrenalin is pumping and everyone else around is tearing off.  Adrenalin keeps hiding the true cost of the damage you are doing to your muscles and your prospects of running a good marathon - adrenalin prompts the the release glucose from your liver so you feel a buzz of energy, and reduces perception of pain and fatigue, which is great for a 10k, but not really what you want for a marathon.

For a marathon you need to make sure your glycogen stores in your liver don't empty too quickly, but are called upon steadily through the race.  If the body spots that liver glycogen levels are getting too low it actually creates the emotion of fatigue and slows us down, from their on it's a battle to stay focused and keep the adrenalin pumping because if you don't your body starts shutting down.  Once the adrenalin starts subsiding and the true state of damage and glycogen depletion is revealed it can be rather difficult to keep going.  I believe this is the wall that so many marathoners hit - it's not actually a hard limit of glycogen depletion but the central governor shutting things down as things have gone too far out of homo-stasis at too fast a rate.  These are the key reasons way it's so hard to run a marathon well.

How might an average runner achieve optimal pacing?

So how does an average runner run the optimal pace?  Being realistic, practice, and using tools.

Being realistic is really down to judging just what time you are likely to be able to achieve.  Marathon time calculators like the McMillan are based on what elite runners can do rather than average runners.  Average runners rarely have the aerobic, structural and metabolic resilience to be able to convert their 10k times to great marathon times like the elites.  This average lower reliance than the elites means you need to be more conservative about your time goals.

Practice is about running the target race pace regularly, getting a feel for the breathing, cadence and general feel for that pace.   As you approach your peak training and go into taper you need to speed more and more time at this pace to dial into it.  Dialing into the intensity/breathing is important is you need to run any hills at the same intensity and not judge them by pace.

Tools, here is something that may well be the crucial bit to helping elevate an inexperienced runner into a pacing god.  Heart Rate (HR) monitors are great for telling us just how hard our bodies are working.  While adrenalin may hide our actual effort level making fast pace seem easy and HR monitor will tell us exactly what is going on.  It's the face pace that does the damage so if the HR monitor values are high is indication that are likely incurring more damage than we are aware of.

HR monitors aren't flawless  - they can mis-read at times, and the thanks to natural HR drift the HR trace for optimal even pacing leads to a steady increase in HR from start to finish.  The mis-reading is typical down to poor/compromised contact, wetting a HR strap properly helps avoid this.  With the HR drift just what HR to aim for each stage is something that is likely to be personal, different runners experience different amounts of HR drift, and adrenalin can also elevate the HR for a given pace so if it goes up and down through the race what to aim for can change.

As a starting place one can use the HR guide suggested by the MARCO calculator:

    http://feelrace.com/fr.pl?th=MARCO

From the Loch Katrine marathon that I ran 10 days ago I had a bash at using the MARCO HR guidelines. In a practice run 6 days before the marathon I ran a half marathon route on similar undulating terrain using the HR profile suggested by the MARCO calculator.  What I found is that my first mile was 15 seconds per mile too slow compared to the MARCO calculator, but in the second half on my run I had to run 30 seconds per mile faster than my planned pace.  This trail run told me that my starting HR needed to be higher and my HR drift was slower so I didn't need to target increasing my HR through the race at quite the same rate.

Race day is where it counts, does pacing by HR work?

Come Loch Katrine race day I used my HR monitor and the general principle of increasing HR through the race suggested by the MARCO calculator with tweaks based on my experience with my HR trail run, and also tweaking it on the day.  My aim for the day was to use the marathon as a training run so not push on too hard, and if possible set myself a PB with a target time of 3:30.

The Loch Katrine marathon is extremely hilly so each mile I either got ahead or behind my target average pace of 8min/mile, so I had to trust that pacing would even out.  I hit the turn around point in 1:45:09 which is far more luck than judgement to get that close, but getting so near to this just by using HR and tweaking it little bits each mile to how things were progressing is what got me in the right ballpark.  The tweaking I was doing was to lower my average HR I was targeting for each mile as my HR drift was less than I expected even compared to my half marathon trail run.

Thanks to less hills in the miles after the half marathon point by mule 16 I got ahead of my 8min/mile target without needing to up the intensity, but once I hit the hills between mile 17 and mile 22 my average speed dropped and I down a couple of minutes my the top, but as the downhill miles came I gradually got back on target.  All the while I was using my HR monitor to judge whether to slow down or speed up.

Once I got to mile 23 I was only just behind my target pace, and although it was only meant to be a training run I found myself picking up the pace, really just for fun.  My energy levels had been rock solid all through the race, my legs were quite fatigued from all the downhill miles but I overall I felt great so just pushed on.  The nearer I got to the finish the more I took the breaks off and ended up finishing the last mile in 6:10, and the last quarter at 5 min/mile pace.  Within the crazy finish I would have hit my target of 3:30 quite comfortably, but with the fun last few miles I did it in 3:26:50, nearly a 6 min PB on much hillier course than the Edinburgh marathon course where my previous PB of 3:32:26 was set.

Now I am capable of running a faster marathon, as I wasn't racing it, so I ran the first 23 mile at a slower pace than what I likely capable of.  Running such a big the negative split I did thanks the overly fast last mile isn't optimal in any way shape or form - this occurred because I was playing, not racing.  If I were to race a marathon I'd run the whole thing close to same intensity and pace.  I would certainly struggle more in the last few miles if I were racing simply because of the accumulated fatigue associated with running faster, but that's racing.  My target for sure would be even intensity and even splits.

When scaling up to ultra-marathon I have also found running by HR to be really beneficial.  In my three ultras last Autumn I raced them all far better than my previous ultra record had suggested likely.  One part of this improvement was changes in my diet to higher fat/modest carb diet so I have become better are burning fats and sparing carbs, but a big part of it is getting my pacing right - in my case by running to a constant HR. Targeting a constant HR lead me to run the first halves comfortable and then finish strong.  In my analysis of Devil O'Highland splits my own first half/second half pacing had a small positive split, but 0.7% different pacing than the winner, who just so happened to also run the strongest second half of all the people last year, and the closest to the pace that Jez and Lucy used.

Could it be coincidence that I paced in a very similar way to the best of the best or is it an indication that they run with an even pace and that running with a near constant HR is a good proxy for this intensity and pace?  Personally I can't think of more compelling indicator of just how effective pacing by HR can be.

Probabilistic pacing

Since even and negative splits are common mantra's for runners, me advocating the same really isn't novel.  My positive experience and advocacy of pacing by HR aren't unique either.  Before I wrap I'd like to put forward an idea/why of thinking about pacing that I haven't see discussed before - Probabilistic Pacing.

What is Probabilistic Pacing?  My idea is that we can view our race statistically, where each mile we run and how we run it effects the probability of achieving a particular goal be it time based, place based or just ability to finish.  What you do in each mile can improve your chances of succeeding in your goal or diminish it.   I believe we can simply view this as at high level of conscious thought - i.e if I push on too hard up this hill I increase the risk of cramp on the other side, or depleting my glycogen reserves too much, or to decide to hold back on descent to avoid going over an ankle, this high mental level of Probabilistic Pacing strategy could be partly thought as our Tactical brain.

I don't believe this idea of Probabilistic Pacing is just high level associated with conscious thought processes, I believe the Central Governor Theory suggest that at a sub-conscious level our brain/central nervous system is making calculations all the from external and internal factors to judge whether we are pushing our bodies too far out of homo-stasis as to be safe. If the Central Governor judges what we are doing as potentially damaging or dangerous then passes on it's assessment as the feeling as pain and fatigue to the conscious part of brain.  The further out of homo-stasis we get, or look likely to get, the stronger the Central Governor will dampen our ability to push on, hitting the wall/boning is likely more a manifestation of Central Governor taking charge than actual complete exhaustion.  Conversely if Central Governor judges what we are doing as safe it leaves us alone to run a good pace.

The high level tactical side to Probabilistic Pacing is really about us consciously setting a particular pace that will most likely get us to finish in one piece and at our goal pace/position, as well as working out what our body needs right now to maintain it's workload and also what we'll need next.  In an ultra-marathon this type of mental process has to include thoughts about navigation - do I need a check the map, is the route clear/familiar enough for me not need to check?  Do I need to eat now or later, do I need to drink?  Do I need to pick up some more clothing at the next check point?  Will I need my head touch?  In all these questions we are weighing up the probability that different help or hind our progress.

Probabilistic pacing relates to how fast or slow to run each section in that if we run faster we increase the probability that we'll deplete glycogen more, increase heat stress, sweat more, be able to digest less so absorb less calories and less fluid - running faster reduces can even reduce the probability of finishing at all.  If we run slower we help our bodies stay closer to the safe homo-stasis that it loves, and increase our chances finishing significantly.  However, if we want to achieve a personal best then we have to make a judgement and work out just how much risk are we willing to take with crashing and burning before the finish.

Now the Central Governor is also making these computations and if it decides to take control and cause massive fatigue then it doesn't matter how much me want to finish in certain time, if it feels that you are endangering yourself then it'll call a day and we can very rapidly feel massively fatigued and unwell. The Central Governor does like suddenly changes, non linear events are very hard to judge so it's natural for our safety systems to be conservative.  However, if we keep things smooth and linear our Central Governor is able to trust in what we are doing more and less likely to shut things down. An analogy that springs to mind is that boiling a frog, if you toss it into boiling water it'll jump out, while if you lay it cool water and let it slowly warm up it won't notice that things are getting hot.

Even pacing has the advantage that our bodies systems are steadily taxed and in way that is linear and predictable.  If the Central Governor sees that we are steadily depleting glycogen but at the rate we are burning it we will still have a safe amount left in our liver by the finish then it'll be happy and let us continue.  If we start fast or do a surge we inject a rapid and non-linear increase in rate of glycogen depletion, the heat stress on our bodies rapidly rises, our reserves of fluids get more rapidly depleted, again it's non linear, a modest increase in speed and we have to sweat much more, all of this is noticed and taken into account of by the Central Governor and makes it all more like to decide to create the fatigue that slows us down.

Listen to your heart

This probably all sounds rather complicated.  How are we supposed to use this in our next marathon or ultra marathon?  My advice is simple, listen to your heart.  I don't mean in the happy clappy, spiritual way, I mean quite literary, your heart is one of the best measures of physiological and physiological stress. The fantastic thing is we now have HR monitors that allow us to track ever beat.  We can now look down to our wrist and immediate now just how hard we are working.

With pacing by HR the absolutely simplest way is to run to constant HR.  Due to HR drift this will lead to your slowing through the race, but as long as you pick as sensible target HR this slowing shouldn't be too dramatic and just lead to a modest positive split, so it might not be optimal but it will be not far off.

A refinement on just running against a constant HR is to factor in HR drift so that your pacing goes from a small positive split back to a even or slight negative split.  The MARCO online calculator can be used as a guide for marathons, but as I've found out the HR drift it assumes may not be appropriate for you.  Using your HR monitor in training and seeing how pace and HR drift are associated can give you an idea what is appropriate for yourself.

The nice thing about using HR as guide to pacing is that it works for ascents and descent telling you exactly how hard it's safe to push on up and hill or how fast you can safely run the descent.  It also tells you when heat stress is affecting you, if it's a hot day your pace for a given HR will be lower, but as we sweat more and use more glycogen when we are hot we can't race as fast when it's hot anyway so having the HR reading guide us to slowing down is exactly what we want.

If you are using your HR monitor as a guide during a race and find that you a feeling better than expected, or worse then your can up you target HR slightly to adjust things to speed up or slow down. I used this strategy when I did my three ultra's in the Autumn of 2013, each time I was hit with cramp I dialled by the intensity, reducing my target HR by 5 bpm till any further hints of cramping had subsided then I let the HR target rise back up.

One can also look at the average HR you set as a target in terms of probabilities - which brings us back to Probabilistic Pacing concept.  Targeting a higher average HR will lead to running faster, but increase the risk being unable to maintain the pace or worse failing completely, targeting a lower average HR will lead to slower time but much better chance of finishing.  Judging the right HR to use on the day is difficult, but if you've got a HR record of previous events then you can use the average HR as a basis. If you don't feel as strong as the previous race then it is probably sensible to target a lower HR and if you feel good in the second half up the HR value.  If you feel stronger then a higher average HR might be attainable, but... if you are fitting your HR for a given pace will be lower.   Through tracking average HR and drift from training and other events look for where you feel might be appropriate come race day.  Then on race day itself adjust as necessary for how you feel.

By using your heart as guide what you do is provide a nice stable physiological load on your body that enables your Central Governor to work with nice linear changes in your homo-stasis, it doesn't get any sudden shock and doesn't panic such as making like you feel like you've hit a wall.   By working so closely with your body it will allow you to achieve much more.

Listen to your heart and your body and mind will be strong.
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