# Help me learn about how VO2max, MHR, and LT are related



## Woof the dog (Jan 28, 2004)

After reading a number of chapters of Brooks' exercise physiology, I am trying to clarify these concepts for myself. Help if you know that you really do know this.

Vo2max is max intake of oxygen per kg body per min (or max absolute volume). LT is the point of lactate inflection in the blood from base clearance rate, as measured by your % of Max heart rate and occurs at 80-90% of max heart rate in trained individual. Max heart rate is self-explanatory. If you ride hard enough, you will cross your LT, and after a short time, you must slow down. 

I am a bit unclear on these: Does VO2max occur at max heart rate, or if not, how many % lower than your max heart rate? More importantly, why?

also, I have a feeling VO2max is reached past your LT (as per above question), right?

big thanks!

woof the dog


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## sdeeer (Aug 12, 2008)

Woof the dog said:


> Vo2max is max intake of oxygen per kg body per min (or max absolute volume). LT is the point of lactate inflection in the blood from base clearance rate, as measured by your % of Max heart rate and occurs at 80-90% of max heart rate in trained individual. Max heart rate is self-explanatory. If you ride hard enough, you will cross your LT, and after a short time, you must slow down.
> 
> I am a bit unclear on these: Does VO2max occur at max heart rate, or if not, how many % lower than your max heart rate? More importantly, why?
> 
> also, I have a feeling VO2max is reached past your LT (as per above question), right?


Look up the fick equation. VO2 = Q * (a - v). 

VO2 is oxygen consumption is L/min (ab) or ml/min/kg relative to BW.

Q is cardiac output which is the product of Heart Rate and Stroke volume.

a - v is the arterial venous difference.

In theory, maximal heart rate should coincide with maximal VO2 uptake. 

The VO2 you can acheive durring the test is partially mode dependant. For example, runners on a treadmill will likely get a higher VO2 than on a bike and vice versa. Also, X-country skiers often get very high VO2's when they do the test doing a whole body activity simialar to XC sking. (due to more tissues using O2 during exercise).

VO2 maxis basically as you explained. The maximal amount of O2 you can conusume during a maximal effort. Some will aruge that true max has to be repeated (within a 10 minute period) after teh first test. A one time test is more correctly called a VO2 peak test. VO2max is mode dependant (bike, treadmill, etc).

Just a quick reply......


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## tom_h (May 6, 2008)

*Lactate Threshhold*

Note that for most people, a more practical method of estimating your lactate threshhold, is to do an all-out, race-pace time trial for 60 (or 20) minutes.

Your average heart rate (or power, if using a powermeter) during the 60 min TT is your "HR @ LT" or "Power @ LT", and is the basis for setting training zones, under most programs.

Because even a 60 min TT can be a problem (motivation, traffic lights), it's also common to do a 20 min TT, and take 95% of that , as your LT HR or power.


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## asgelle (Apr 21, 2003)

tom_h said:


> Your average heart rate (or power, if using a powermeter) during the 60 min TT is your "HR @ LT" or "Power @ LT", and is the basis for setting training zones, under most programs.


Be careful. Power at LT can only be defined in terms of a blood lactate response (though there are scores of such definitions). 60 minute power is generally higher than any of the accepted definitions of LT.


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## zender (Jun 20, 2009)

V02 max is above your LT whether measuring HR or power.

Apologies if this is redundant from your reading: 
For a healthy individual, at "rest" your body operates purely aerobicaly, you produce no excess lactate. All ATP is produced by oxidation of carbon all the way to C02 which you can get rid of via your lungs. V02 is a measure of how much 02 you are consuming - all of which is converted to C02 - so is an indirect measure of how much ATP you are producing aerobically.

At some point as you increase excerise intensity, the ATP requirement exceeds what you can generate aerobically. Some ATP is produced anaerobically. The "waste" product of this anaerobic metabolism is lactate (technically, it's pyruvate, but if pyruvate is not converted to lactate, anaerobic metabolism cannot continue). You cannot get rid of lactate via the lungs, it accumulates in your tissues waiting to be converted back to pyruvate and ultimately C02 when you stop using anaerobic metabolism.

The key is that as you increase your effort it's not a simple switch over from aerobic to anaerobic metabolism - you continue to increase BOTH the aerobic and anaerobic contribution to ATP production. 

LT is the point in your effort (however you measure that - HR, power, speed, whatever) when lactate begins to accumulate in your tissues. Below this level, in theory, you can excercise until you run out of stored energy (fat, carbs, protein) or the planet runs out of oxygen. If you excercise above this intensity, you will eventually need to stay BELOW this intensity in order to metabolize that lactate to C02 (aerobically). You can measure blood lactate by drawing blood as you excercise or one of the estimated methods mentioned by the other posters.

V02 max is the maximum amount of oxygen you can consume in a given time. An indirect measure of how much ATP you can generate aerobically. This occurs at an effort level above your LT . You can still increase effort above this, but it will be purely anaerobic so you will accumulate lactate very quickly.


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## sdeeer (Aug 12, 2008)

zender said:


> *For a healthy individual, at "rest" your body operates purely aerobicaly*.


This is not fully true. Red blood cells do not have a mitochondria and rely on glycolysis for energy production (which does not use O2). They are constantly producing a low level of lactate (typical fasting lactate in ~1.0mmol).



zender said:


> V02 is a measure of how much 02 you can consume over time -* all of which is converted to C02*.


Metabolic water is also produced. O2 is used to make CO2 and H2O.




zender said:


> At some point as you increase excerise intensity, the ATP requirement exceeds what you can generate aerobically. Some ATP is produced anaerobically.


"Anaerobic" metabolism (or glycolysis) is always occuring in exercising muscle. Lactate is not a waste product, but an important metabolite. Lactate is measured in the blood, and not tissue (in most cases). It accumulates in both blood and tissues, but is cleared from tissues rather quickly. The heart and liver are the main sites that use lactate as a fuel during exercise. 




zender said:


> you continue to increase BOTH the aerobic and anaerobic contribution to ATP production.


correct


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## zender (Jun 20, 2009)

/sigh
It's a bike forum. I took a few liberties in the details to try and keep it from turning into a wall-of-intermediary-metabolism-text. (e.g. you'll note the quotes when describing lactate as a waste product). I also omited a thousand other details, but the point was to explain how V02max is higher than LT in most circumstances, which was the OP's question.


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## Woof the dog (Jan 28, 2004)

thank you both. I was acutely aware of glycolysis being the first step in energy production from carbohydrates, as far as I know not only in exercising muscles, but in any cell in the body (ditto on rbc's). I noticed Brooks et al have emphasized 'lactate shuttle' (intracellular and systemic) in huge detail, and rightly so.

I really do highly recommend this book (I bought mine on amazon for like 20 bucks, Exercise physiology: bioenergetics...), it gives a molecular biologist like myself a greater appreciation for metabolism and a fresh perspective on other things. New edition is coming out in a year or so.

woof the god... no, dog.


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## jlwdm (Nov 7, 2009)

From a cycling standpoint work with your LT, the others don't matter. So don't get to hung up on them.

Jeff


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