What % MHR for marathon (Page 2)

Well tipically LT is defined differently depending on the level of fitness. I recognize that it is impossible to define LT once for all because you will bever have the chance to check the lactate levels unless you go with a special professional testing session but for most of us will not be the case.

If you define your LT as the average you keep for 1hr running (at maximum) then of course your 10k average is ABOVE the LT defined.

If you define (like me) the LT as my 10k race, then 10k pace average = LT and no discussions.

You will find different protocols to test it but Conconi protocol seems to be the most used and it matches with 10k pace

Huh???

The most accepted "definition" for LT is the HR/pace point at which your accumulation of Lactic Acid surpasses the bodies ability to rid the muscles of it and it matters absolutely zero when it comes to level of fitness for what it is and how it is measured.  The level of it will increase as you get fitter, bt the definition and the measurement of it are exactly the same process.

Anything short of a blood lactate test will only be an estimate.  And even then, it has to be done correctly with progressive ramping up of pace (typically 5 minutes at a pace before going up the next step for 5 minutes) and blood samples taken at prescribed times.  The point at which the lactate starts to increase at a certan rate is your LT.  It is below your VO2 max which is the point where you are taking in maximum oxygen that your system will allow.  In the most elite and efficient of runners, the two can be pretty close.

And I personally have NEVER heard of anyone saying that LT pace is 10k for faster runners.  Generically speaking it is the pace that someone can hold for an hour time period.  For slower runners that is a 10k, yes.  For medium runners that is a 15k and for fast runners that is close to a 1/2.

The other way to look at it is using McMillan as mbmoran2 is or VDOT as others recommend.  You put in your latest stand alone race result and they have worked out the prescribed ranges for you.  Again, this assumes correct training for the distance and a solid dose of HTFU to mentally be able to hold it in a race.

Pfitzinger's tempo pace discussion:

Three levels:

Easy
Medium
Hard

So much easier. 

I'm stealing this from another site.

Food for thought:

I agree with the sentiment EXCEPT when the goal is 'just' to go the distance.  At times, that is competition and satisfaction enough.

But for all the other times...if it's a race, then RACE! 

If the goal is to just finish the distance, isn't that already pushing yourself?  Why not see how hard you can go?

Source # 1

Go too hard and you might not make the distance.  And the first time you go pretty much any distance, there's satisfaction/achievement/learning for most regardless of how hard you pushed or whether or not you 'laid it all on the line'.  But, like I said, most times I agree with the sentiment completely.

That's the point. In terms of distance, it is a different "definition" for different fitness level. Than about the definition on lactate level accumulation is of course the same for everybody.

Anyway, even if I run the 10k in 35' or 40', I see Conconi for myself saturating always at 169 or 170 bpm.

Your last long run is very encouraging.  Notice how your HR was steady along with your pace without it climbing as you ran - during you MP part.  That pretty much means you are not accumulating lactic acid, hence are below LT.  Definitely go for the 3:16.  I would not deviate from the plan until after half way through.  You may be able to go faster - really go by feel in the last six or so miles.  You should have a pretty good feeling for whare you are relative to your LT at that point you may find you can even oick it up by a few minutes.  Just get a good taper in now.  As they say, you can't help your race much now but you sure can hurt it.

PS I may come down town to chear you all on.  It kills me not to be running this thing-inaugeral event in my town, but I have a HIM the following week.

Thanks RC...

Here's a good article from NYRR on marathon pacing strategy.

http://www.nyrr.org/resources/training/marathon_strategy.asp

That sounds like what I said:

"A good bet for Novice and Intermediate Competitors is to start at the same pace as you averaged for your last long run and hold that speed to 20 miles. From there, hang on as best you can. You may even be able to pick up the pace if you've trained well."

Another tid bit

I usually will pass the first rest stop or so until congestion wears down, but after that I grab a gatorade and a water at each station-except when I hit the gels and then I just take a water.  I know I lose some time doing this, but it beats bonking.  Funny thing, a friend of mine who is also a sub 3hr marathoner does the same thing.  Together we have run probably 15 or so marathons and independently came to the same conclusion/practice.  What you are fighting is the dehydration.  As you dehydrate your blood becomes more viscous due to lower plasma levels.  You heart has to beat harder to distribute the blood, as a result your heart rate at a given pace has to increase.  Before you know it your LT is actually at a slower pace than it was at the start of the run.

Huh?

I think the issue is fuel, not dehydration.

Glycogen depletion does not have much to do with the cardiac drift - the increased heart rate late in the race.  It does have a lot to do with cramping and muscle fatigue though.  The heart muscle is very much different from the other muscles in the body with respect to its  contraction.  Cardiac drift is mostly about hydration, reduced plasma volume and core body temperature.

No it doesn't .......

My point is that dehydration in a marathon has little to nothing to do with increased heart rate, unless you are severely dehydrated, which would be an exceptional case.

What is Cardiovascular Drift? If you begin a 90 minute steady state ride on your bicycle trainer at a controlled intensity, your heart rate may be 145 after 10 minutes. However, as you ride and check your heart rate every 10 minutes, you will notice a slight upward "drift". By 90 minutes, your heart rate may be 160. Why is this happening if intensity is held constant? There are two explanations. As you exercise, you sweat (dah). A portion of this lost fluid volume comes from the plasma volume. This decrease in plasma volume will diminish venous return and stroke volume. Heart rate again increases to compensate and maintain constant cardiac output. Maintaining high fluid consumption before and during the ride will help to minimize this cardiovascular drift, by replacing fluid volume.

There is also a second reason for the drift during an exhaustive exercise session. Your heart rate is controlled in large part by the "Relative" intensity of work by the muscles. So in a long hard ride, some of your motor units fatigue due to glycogen depletion. Your brain compensates by recruiting more motor units to perform the same absolute workload. There is a parallel increase in heart rate. Consequently, a ride that began at heart rate 150, can end up with you exhausted and at a heart rate of 175, 2 hours later, even if speed never changed!

Stephen Seiler PhD  Full Professor at the Institute of Publich Health, Sport, and Nutrition University of Agder, Kristiansand, Norway

I tend to agree with that.  As you dehydrate you would see a change in the plasma density.  So staying on top of hydrating is important.  But as Scout mentions, it does take a lot of fluid loss to make a significant dip.

Another explanation is heat build up.  The majority of the energy you use in running is lost as heat (the body is not that efficient of an engine overall).  Your body regulates that heat by sending blood/fluid to the skin to sweat and dissipate that heat.  As you go longer, your body is working harder to keep up with that heat accumulation.  The heart has to work harder to keep the blood flowing to allow you to cool down.  So at the same effort, your heart rate is increasing over time to keep up with the cooling system.

There is a much greater risk of suffering from hyponatremia than there is from dehydration in a marathon.

 Your explanation is the one that I have most ordinarily seen on cardiac drift and yes it has a lot to due with dehydration, plasma viscosity and its impact on blood flow and core temperature.  This has a lot to do with why fast marathons are run in colder conditions.  I provided both hydration and glycogen explanation because that was in the exercise physiologists report (to be fair in citing).  That is the first report I have read that said that muscle fiber recruitment contributes to cardiac drift.

There have been no excercise related deaths from dehydration.  There have been numerous from hyponatremia.  The body shuts down and makes you quit before you'd get to the level required from dehydration to kill ...... basically it is almost physiologically impossible to "kill" yourself in a running race from dehydration.  Heat stroke is a different topic ...... that can kill.

Elite marathones race to dehydration, usually with 3 - 5% body weight loss.