What limits 5k/10k speed?

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What limits 5k/10k speed?

Postby jonovision_man » Mon May 04, 2009 9:29 am

I figure over 10k I burn around 800-900 calories. I know that if I'm carb-loaded I should have something closer to 1800 calories of energy stores, plus whatever else I consume before/after/during.

More than enough energy without even dipping into all the fat.

So what gives that feeling like your energy is zapped? It's a tremendous sense of fatigue, especially when you go out too fast.

I'm guessing it has something to do with oxygen and blood? ie. the glucose is there but your body can't burn it fast enough?

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Postby MichaelMc » Mon May 04, 2009 9:58 am

Usually what limits 5/10k speed is lactic acid threshold. Your body produces muscle energy (ATP) three different ways, two anerobic and one aerobic (with oxygen). Depending on the speed and intensity of exercise you use them in different proportion.

Aerobic energy production requires your bloodstream to deliver oxygen to the muscles for energy production. It can burn all types of fuel: Carbs, Fat or Protein, but is limited by the oxygen available at all times. Your lungs and circulation only deliver so much, so fast. you can produce aerobic energy for huge amounts of time, but at a limited rate.

For instant power we can use our quick reserve of ATP and creatine phosphate, (called the phosphate energy system) but we have very little of it: about ten seconds worth is stored. That won't get you far in a race.

There are times when we need more energy than we have oxygen to produce it, so we have Glycolysis which is also anaerobic: it breaks down glucose to make ATP, but without it leaves lactic acid as a by-product. Lactic acid can be used as fuel, but it needs oxygen to become useful. As we go faster and faster the supply of oxygen is limited and eventually the lactic acid starts to build up in your body. There are all sorts of arguments about whether it is actually lactic acid that slows you down or something else that happens at the same time, but when you exceed your ability to process lactic acid into fuel you are living on borrowed time.

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Postby fe.RMT » Mon May 04, 2009 10:08 am

The rumours are true......

2013:
Thanksgiving Day 5k: 27:26

Coming up:
ORW Half Marathon
NYC Marathon 2014

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Postby jonovision_man » Mon May 04, 2009 10:14 am

Thanks MichaelMc - that's great info. I always associate lactic acid build-up with cramps, but from what you're saying it inhibits your muscles far before it get gets to that point.

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Postby 10not42 » Mon May 04, 2009 11:30 am

Depends on how fast you are. Assuming a 10k of 40-60 minutes, the 10k is run at, or slightly higher intensity than LT, so your vLT (speed at LT) is probably the main limit.

If you run a 5k under 20 minutes or so, then you are quite a bit beyond LT, and starting to approach VO2 max, so your vVO2 is probably just as important as vLT.

When I set my 5k PR, I did a lot of VO2 and lactic buffering training (hard intervals with limited rest), and not a lot of LT work.

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Postby MichaelMc » Mon May 04, 2009 12:17 pm

10not42 wrote:Depends on how fast you are. Assuming a 10k of 40-60 minutes, the 10k is run at, or slightly higher intensity than LT, so your vLT (speed at LT) is probably the main limit.

If you run a 5k under 20 minutes or so, then you are quite a bit beyond LT, and starting to approach VO2 max, so your vVO2 is probably just as important as vLT.

When I set my 5k PR, I did a lot of VO2 and lactic buffering training (hard intervals with limited rest), and not a lot of LT work.


I'd argue that even in a 5k LT is still the limiting factor, but working on VO2 max also serves to improve it. VO2 max is how well your lungs and circulatory system can deliver oxygen to your muscles (and dispose of CO2). The higher that is, the faster you can run aerobically. Of course different people have different efficiency in USING the available oxygen (turning it into speed/distance), too.

Having said that, you only have so much oxygen debt you can run. Once you start producing more lactic acid than you can process, the clock is ticking. The 5k is short enough that smart management will allow you to run it a certain percentage past your LT, but I'd argue it is still limited by the LT. Unless you can finish a race without breathing, it isn't short enough for aerobic energy production not to influence the result.

One could focus exclusively on VO2 max and drag LT up with it (because your threshold is AS A PERCENTAGE OF your VO2 max), but VO2 max work sees the point of diminishing returns pretty quickly. LT training produces results slower, but for much longer. Both count.

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Re: What limits 5k/10k speed?

Postby Jwolf » Mon May 04, 2009 12:26 pm

jonovision_man wrote:...More than enough energy without even dipping into all the fat.

So what gives that feeling like your energy is zapped? ...I'm guessing it has something to do with oxygen and blood? ie. the glucose is there but your body can't burn it fast enough?

Just to add to what the others said-- it's not that your body has started to burn fat, but that it has to slow down to use the lactate and prevent it from getting too high.

Fat burning doesn't really come into play when you're racing at your top speed, even for a half-marathon.

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Postby 10not42 » Mon May 04, 2009 4:15 pm

It's not exactly clear to me what jon is asking, but I agree with michael, if you go out a bit hard in a 10k and your legs feel "dead", you probably have the most to gain by improving your LT.

But, something that wasn't mentioned yet - for me a good taper (yes even for a 5k or 10k) really makes my legs feel stronger late in a race.

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Postby jonovision_man » Mon May 04, 2009 7:29 pm

All I was asking is what limiter keeps the typical runner from going faster on a 5k/10k... where is that sense of fatigue coming from?

For longer efforts at slower paces (ie. marathons or century rides) you don't feel fatigued until you're hours in, and it's because you've depleted your sources of glucose (glycogen stores). Obviously in something short like a 5k/10k the energy is there, but something else is at play.

It seems like the answer is in the lactic acid build-up which beings to inhibit the muscles from performing like they normally would, giving that sensation of fatigue.

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Postby Pat Menzies » Mon May 04, 2009 8:07 pm

Lack of race fitness, not lactic acid. You're asking your body to do something it isn't prepared for.
The races(400-800) that produce levels of lactic acid that are unlike anything any road racer experiences bring on no feeling of fatigue like a long run or race. It's a totally different animal.

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Postby jonovision_man » Tue May 05, 2009 7:15 am

Pat Menzies wrote:Lack of race fitness, not lactic acid.


Obviously any limiter to performance you hit can be chaulked up to "lack of race fitness", if you trained more to move that limiter you'd do better. I'm looking for something more specific, sounds like LT is the likely answer for this distance.

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Postby Pat Menzies » Tue May 05, 2009 7:26 am

Not really. Racing virtually any distance is about all the aspects of fitness, not one factor.

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Postby jonovision_man » Tue May 05, 2009 7:34 am

Pat Menzies wrote:Not really. Racing virtually any distance is about all the aspects of fitness, not one factor.


But not equally.

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Re: What limits 5k/10k speed?

Postby Wu wei » Tue May 05, 2009 10:38 am

jonovision_man wrote: I know that if I'm carb-loaded


Quick performance tip: DON'T carbo-load.
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Re: What limits 5k/10k speed?

Postby jonovision_man » Tue May 05, 2009 11:39 am

mytrilife wrote:
jonovision_man wrote: I know that if I'm carb-loaded


Quick performance tip: DON'T carbo-load.


I suspect you mean don't do the spaghetti pig-out thing the day before, correct?

Most of the nutritionists seem to suggest you should carbo-load by adding a moderate amount of carbs to your diet in the days leading up to the race, though. I don't know if that's really carbo-loading in the traditional sense.

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Re: What limits 5k/10k speed?

Postby Wu wei » Tue May 05, 2009 11:51 am

jonovision_man wrote:
mytrilife wrote:
jonovision_man wrote: I know that if I'm carb-loaded


Quick performance tip: DON'T carbo-load.


I suspect you mean don't do the spaghetti pig-out thing the day before, correct?

Most of the nutritionists seem to suggest you should carbo-load by adding a moderate amount of carbs to your diet in the days leading up to the race, though. I don't know if that's really carbo-loading in the traditional sense.

jono


You don't need to add ANY extra carbs. Period. If you eat after your workouts, you'll top up your muscle glycogen... you're good to go. I eat steak the night before races. My 10k PB is ~35min.

Carbo loading messes up our hormone and insulin levels. My coach is a diabetic and wrote this article:
http://www.ironguides.net/news/104/93.html

But, but... I'm not diabetic?! Doesn't matter... our bodies still have the same insulin and hormonal reaction..
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Re: What limits 5k/10k speed?

Postby Jwolf » Tue May 05, 2009 11:52 am

mytrilife wrote:Carbo loading messes up our hormone and insulin levels. My coach is a diabetic and wrote this article:
http://www.ironguides.net/news/104/93.html

But, but... I'm not diabetic?! Doesn't matter... our bodies still have the same insulin and hormonal reaction..


Thanks for posting that, Greg.

People do try to mess with their hormones and regulatory systems way too much-- it's just not necessary.

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Postby La » Tue May 05, 2009 12:16 pm

I agree. Personally, I think that post-workout recovery nutrition is far more important than anything else you eat in the days leading up to a race. Actually, the one caveat would be not to eat anything that isn't easily digestible in your system.

The only other thing (from a nutritional perspective) that you might want to look at is how your Carb/Pro/Fat percentages break down during a typical week. If you discover that your % of carb intake is low (e.g., below 60-65%), then you might want to readjust that. Most athletes want to have about 65-70% of their calories coming from carbs. If you're doing that, then there's no need to carb load.
Last edited by La on Tue May 05, 2009 12:21 pm, edited 1 time in total.
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Postby Dstew » Tue May 05, 2009 12:18 pm

There are also psychological issues and my demon is the 10 K race.

I am still working on that.

For the 5 K race I tried one training tip I found and that is to run 1 K at your race pace, rest and repeat five times. To show the mind that your body is physically able to run as fast as it can.

For a 10 K, not a clue as nothing seems to have worked in the past. Right now trying to do some longer tempo runs of 12 K or so so that a race pace over 10 K is not such a shock. In the testing phase.

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Re: What limits 5k/10k speed?

Postby jonovision_man » Tue May 05, 2009 12:18 pm

mytrilife wrote:
jonovision_man wrote:
mytrilife wrote:
jonovision_man wrote: I know that if I'm carb-loaded


Quick performance tip: DON'T carbo-load.


I suspect you mean don't do the spaghetti pig-out thing the day before, correct?

Most of the nutritionists seem to suggest you should carbo-load by adding a moderate amount of carbs to your diet in the days leading up to the race, though. I don't know if that's really carbo-loading in the traditional sense.

jono


You don't need to add ANY extra carbs. Period. If you eat after your workouts, you'll top up your muscle glycogen... you're good to go. I eat steak the night before races. My 10k PB is ~35min.

Carbo loading messes up our hormone and insulin levels. My coach is a diabetic and wrote this article:
http://www.ironguides.net/news/104/93.html

But, but... I'm not diabetic?! Doesn't matter... our bodies still have the same insulin and hormonal reaction..


10k you don't burn more than what, 800 calories? For a 5k/10k most people are going to be fine on their normal diet.

But for longer stuff I'm not as convinced... Nancy Clark's book has a graph that shows muscle glycogen after a hard work-out and how well it's replenished on a 2/3 carb diet vs how poorly on a protein/fat diet. (I don't have it in front of me, can post more details when I get home). It takes literally days longer on a lower-carb diet vs a higher-carb one, if you're going to go long then that's something you have to consider.

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Postby Wu wei » Tue May 05, 2009 12:21 pm

La wrote:I agree. Personally, I think that post-workout recovery nutrition is far more important than anything else you eat in the days leading up to a race. Actually, the one caveat would be not to eat anything that isn't easily digestible in your system.

The only other thing (from a nutritional perspecive) that you might want to look at is how your Carb/Pro/Fat percentages break down during a typical week. If you discover that your % of carb intake is low (e.g., below 60-65%), then you might want to readjust that. Most athletes want to have about 65-70% of their calories coming from carbs. If you're doing that, then there's no need to carb load.


Do you find it a bit difficult to know what your ratio is? I'm not sure I'd want to take the time to calculate.... or even how?

The type of training I do is not focused on high volume aerobic work... so my training mix is different than most, and I find I need a lot more protein to maintain muscle mass.
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Re: What limits 5k/10k speed?

Postby La » Tue May 05, 2009 12:24 pm

jonovision_man wrote:But for longer stuff I'm not as convinced... Nancy Clark's book has a graph that shows muscle glycogen after a hard work-out and how well it's replenished on a 2/3 carb diet vs how poorly on a protein/fat diet. (I don't have it in front of me, can post more details when I get home). It takes literally days longer on a lower-carb diet vs a higher-carb one, if you're going to go long then that's something you have to consider.

But your question was about 5/10K races, not going longer.
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Re: What limits 5k/10k speed?

Postby jonovision_man » Tue May 05, 2009 12:27 pm

La wrote:
jonovision_man wrote:But for longer stuff I'm not as convinced... Nancy Clark's book has a graph that shows muscle glycogen after a hard work-out and how well it's replenished on a 2/3 carb diet vs how poorly on a protein/fat diet. (I don't have it in front of me, can post more details when I get home). It takes literally days longer on a lower-carb diet vs a higher-carb one, if you're going to go long then that's something you have to consider.

But your question was about 5/10K races, not going longer.


OK I was confused with mytrilife's response, he seemed to be saying you never want to carb load...

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Postby La » Tue May 05, 2009 12:28 pm

mytrilife wrote:Do you find it a bit difficult to know what your ratio is? I'm not sure I'd want to take the time to calculate.... or even how?

I use a program called nutridiary.com. You just have to log a typical day's food in and it will tell you what the percentages are (as well as total calories, grams of carb/pro/fat, vitamins, etc.). Over time, I just know what and how much to eat - I don't have to log all the time. But if you never have, it's an interesting (and sometimes eye-opening) thing to do.
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Re: What limits 5k/10k speed?

Postby La » Tue May 05, 2009 12:32 pm

jonovision_man wrote:
La wrote:
jonovision_man wrote:But for longer stuff I'm not as convinced... Nancy Clark's book has a graph that shows muscle glycogen after a hard work-out and how well it's replenished on a 2/3 carb diet vs how poorly on a protein/fat diet. (I don't have it in front of me, can post more details when I get home). It takes literally days longer on a lower-carb diet vs a higher-carb one, if you're going to go long then that's something you have to consider.

But your question was about 5/10K races, not going longer.


OK I was confused with mytrilife's response, he seemed to be saying you never want to carb load...

jono

I think he was saying that, but perhaps the term "carb-load" is misunderstood and mis-used. If you eat the appropriate amount of carbs on a daily/weekly basis, and re-fuel properly after workouts, then you likely won't have to make a deliberate choice to eat extra carbs in the week leading up to a race. The proper balance at all times will usually yield better results than drastically increasing one macro-nutrient for a short amount of time.
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