It's 80-95% of your Max.HR, depending on fitness. <br /><br />Generally, it's the highest HR you can sustain for <br />40-60 mins. <br /><br />More importantly, what's the power your produce <br />at LT? <br /><br />-m
[quote author=CogLoose link=board=19;threadid=2622;start=0#22414 date=1036979088]<br />More importantly, what's the power your produce <br />at LT? <br /><br />-m<br />[/quote]<br /><br />Thats a good point, big deal if you can ride all day at 97% of your max if your only putting out 100watts <br /><br />85-95% of your max is generally around yout AT<br /><br />cheers!
Best way to find it out is to have your lactate threshold measured directly in a lab. But these needs to be done regularly to have a benefit. Where do you come from? Perhaps the others can suggest places where you can go?!
You'll need to have blood taken, generally from either finger ***** or ear lobe, whilst conducting various tests in a lab. The HR that is elicited by your LT is in most trained people considerably lower than your race effort. Typically, the power output that is elicited by your LT is ~ 20% lower than that, that can be sustained for ~ 1-hr TT. <br /><br />Lactate threshold is generally defined as a 1mmol increase in lactate over baseline levels, with trained cyclists able to hold this level for up to more than several hours.<br /><br />LT is not the highest (average) HR that can be sustained for 1-hr or any other time period. HR has nothing to do with LT, i.e., LT is a measure of lactate in blood, hence requiring blood samples to be taken.<br /><br />The power output that is elicited at LT, is a good indicator of performance, as is power at TT pace (about 20% higher than LT), and power at VO2 max (e.g., at the end of an incremental test to exhaustion).<br /><br />It's also imperative to realise that LT will be affected by prior training (e.g., if you train the day before a test) and by your diet and how much glycogen you have stored within your muscles and liver, i.e., if you are glycogen depleted the results will be skewed.<br /><br />Ric
To add to Ric's list, the protocol used during the test (e.g. the ramp rate, etc.) is also very important. Changing the protocol will mean that results of different tests cannot be compared directly.<br /><br />And although I agree with all of the comments made by Ric, predictions of LT using various means alows people who dont have access to labs/funds for scientific suport/novices to get an indication of their performance at this level. If you do this kind of 'field' test, remember that it doesn't give you a direct measure of LT, or heart rate/power output at LT.
The term Lactate threshold it is confused many times by most people, including most physiologist. There are many theories like the increase of 1 mmol above baseline or the blood concentration of 4mmol/L, also called OBLA (Onset of blood lactate accumulation). However, the body doesn´t have a "breakpoint" at which starts a lactate threshold. You can ride, eg, for 45 min at a blood lactate concentration of 6mmol/L but cannot do it for 2h. however (and again it is just an example) you can ride for 2 hours at a blood lactate concentration of 2.5 mmol/L but cannot sustain it for 5 hours....and etcetera, so when we talk a bout a "lactate threshold" what do we mean?; LT for 45t min?, or LT for 2h? or LT for 3h?....<br />Bottom line is the exercise intensity at which your muscle starts accumulating lactate and acidosis starts to increse, since your muscle cannot clear it out and builds up. Whatever the grade of lactate accumulation, there is always a "steady state" of lactate accumulation and this steady steate is sustainable overtime depending on the lactate accumulation. This means that we can reach a steady state of 5-7 mmol/L over 45-50 min but after that due to the incresed glucolitic flux the lactate concentration will build up more and power won´t be able to be sustained. Also we can ride at a "steady state" of , e.g., 2.5 mmol/L for 2.5 hours but after that the muscle won´t be able to keep up with that steady state and less lactate will be oxidated and it will build up more and that power won´t be able to be sustained more. It sounds a litle complicated and I don´t know If I am explaining it very well. ???. It is also important to know that not eveyone´s muscle metabolism is the same. The same blood lactate concentration is not the same for most of the people as most testers think. That is, at a 4mmol of lactate I can do a moderate workout but someone else can be doing a very hard exercise. So we cannnot just go by absolute blood lactate numbers. We have to measure what´s our individual exercise intensity at which we start to build up lactate and identify specially 2 exercise intensities for that: one at "moderate" exercise intensity, which would represent the amount of time we can sustain at that moderate intensity, generally hours and and the other the exercise intensity at the one we start building up much more lactate, This last intensity will be valid for TT´s and climbing.<br /><br />For this, it takes cualified and experienced person as well as an adeccuate protocol.
LT = the point at which lactate begins to accumulate in the blood (i.e. lactate production exceeds removal). Wheras Ric prefers to find this point via a 1 mmol increase in blood lactate, I prefer to determine this visualy off a graph and then confirm this point using breath by breath VCO2 data.<br /><br />IS1 and Ric have made some interesting points. Obviously lactate steady state takes a lot longer to measure than LT using a ramp test, but is perhaps a little more interesting in terms of performance. To add another dimention to this runners look at velocity at LT or VO2max, cyclist should look at power output at VO2 max and LT.<br /><br />There is only one lactate threshold, and not LT's for different times (see definition above). Instead, as IS1 points out people DO have different responses to accumulated Lactate that will result in different performances at different lactate levels and over different times!<br /><br />Prefer not to use AT and OBLA, as many of these terms have been discredited as anything other than reference points and cause more confusion than is needed!!!
It is important to point out, that once you have determined your heartrate at LT, this will surprisingly stay the same for most of your career ! (This works for experienced riders and "older" people, not for young riders with undeveloped cardiovascular systems). What actually changes through training is the power output at LT. Example: Your AT is at a HR of 170/min (very common level). When you are in good shape, you are able to perform at f.ex. 320 W. If you are in bad shape, you might perform only at 200 W for the same heartrate.<br />So it is usually enough to do one lab-test to get the heartrate for your LT. If you want to have a clear statement on your development of performance, you can check the power you are able to perfrom at this given heartrate several times a year on an ergometer or using an SRM system on the road.
What, even when heart rate is so sensitive to temperature, hydration, stress, etc. Would you also have to standardise position on the bike and cadence? <br /><br />Any refs that demonstrate that HR and LT remain at similar levels. Why doesn't LT occur at different heart rates?<br /><br />I do agree though that power output at a certain HR is a good and simple test of training improvement (hence its wide use as a submax test).
As 2Lap correctly implies, HR can vary for a multitude of reasons. Power at a specific HR *will* vary under differing environmental and topographical conditions, even if your fitness is staying steady.<br /><br />If you want to track changes in fitness, and have a power meter (e.g., SRM, Power Tap), why not either do some sort of standardised TT 'all-out', or a test (e.g., incremental to exhaustion) that *doesn't* rely on HR? <br /><br />After all, the purpose of training is (usually) to increase power output.<br /><br />As an aside, i find that my HR *is* significantly different at a given workload, on a day to day basis, depending on whether i'm fully recovered from a previous days effort (i.e., i've raced on two consecutive days, same average power both days, but HR is 10+ b/min lower on the second day).