What exactly does this mean by getting the hr to one number? Like, going until it is just at that single for an extended amount of time? I don't see how you can keep it from fluctuating every few minutes.


Also, does this work with running, too?

A lot of the confusion has to do with vague definitions of terms, I think. In the bike racing world, a "2x20" is a form of interval training, where the rider rides for 20 minutes at their "FTP" power/pulse, then rests, then repeats.

Which begs the question, what's an FTP? Stands for Functional Threshold Power. There are a variety of ways to find your personal FTP, but conceptually, the idea is "the maximum pace / effort that you can maintain for one hour"

Also commonly called "threshold".

The idea being, ride a time trial, as fast and steady as possible, going as hard as you can but not going over that limit where you go "anaerobic" and have to rest.

On a controlled environment like a trainer, with practice, you can hold it pretty steady. Done properly, it hurts, a lot, like a time trial should.

The converse / inverse would be a 20 minute test, like Chris Carmichael and many others recommend. Using a power meter or an HR meter that records averages, you go as hard as you can for 20 minutes, then figure out what your average was. This becomes your target number for the 2x20's.

Your HR won't get to one number during a 2x20 test. I'm not sure who wrote it but if you do the 20 min intervals at constant power your HR will rise quickly at first, stabilize, and then slowly rise during the remainder of the interval.

A true test to determine your Lactate threshold involves a blood test and doesn't take very long. Tests that take longer like 2x20 and 1 hour tests are more useful for determining your threshold power (FTP). During these tests your HR will also drift higher during the test.

If you are training by HR just do the 2x20 test and take the avg HR for the 2nd interval. Alternatively, do a 30 min test and take the average from the final 20 min of the test.

"The lactate threshold is a point during exhaustive, all-out exercise at which lactate builds up in the blood stream faster than the body can remove it. In the lab, lactate threshold tests are performed in a similar manner to VO2 Max testing and use either a treadmill or stationary bike. The exercise intensity is increased in periods of about 4-5 minutes and blood samples are taken with a finger stick at the end of each period. Along with blood lactate concentration, heart rate, power output and VO2 are often measured. This process continues until the blood lactate concentration increases significantly."

That sounds right although it's common to use 3 min steps. The working part of the test takes around 30 min and the hard bit is the last couple of intervals.

When I said the test didn't take long I meant that you aren't at a high power output for very long so you HR doesn't have time to drift like it does in a 2x20 or 1 hr test.

By the way, the link in the stickied thread to determining the max heart rate from the 2x20 test doesn't work anymore.

Thanks for all the replies, it helped spell out some things that I didn't fully get.

I assume that doing a 2x20 or a 1 hour wouldn't crossover from running to biking, but would it still work for finding information specifically towards running?

I am not competitive, but I just like the stats and being able to track changes. It is hard for me to get the full number cycling, because there isn't anywhere to ride without stopping at traffic immediately around. Later when I get some time I might go to a park with a 5 mile loop that is a little bit away from me, or maybe try our my city's old velodrome.

I think this has been the case for a while, now!

The reference to "one number" means that one's LTHR is one number. It's not a range. At one specific HR your lactate levels are not increasing. One beat higher and they are. The objective of a LTHR test is to arrive at that one number. During a performance test like a 2 X 20, your HR will vary a lot, but the output of the test, the average or however it's done in that test, will be one number. It can't be anything else. Whether that one number is the right number or not is another story. It may depend on the motivation of the individual and how they feel that day. OTOH, the blood test is usually quite accurate.

I'm sure it does work with running also, but you'll get a different result, usually higher than for cycling. I don't know the protocol for a running test.

The reality is your LTHR is not one number. It might be one number in a lab if all conditions leading up to the test (including the previous weeks training) are kept constant but the number will vary depending on hydration state, temperature and numerous other variables. And during a TT the number will change significantly from the start to the end of the TT. When riding a TT you can feel when you're at threshold as you start to get a burning sensation in your legs. If you keep your power constant and stay on the edge of that burning feeling your HR will slowly rise.

All true, but I'd be very interested in your response to this article:
https://coachsci.sdsu.edu/csa/vol46/billat.htm

From that article:
It has always seemed to me that a TT rider goes over what is generally accepted as LT (OBLA) by some amount, that amount varying with the length of the TT. The objective being to just barely not lose power due to increasing lactate level and finish the TT at MHR or close to it. Hence you know the power level and leg feeling that will produce that result, though you're going at a little over LT the whole way. You can do that because of your great experience. My conjecture is that if you were to ride at W(OBLA) or a hair below, you wouldn't experience HR drift because of your conditioning. Any truth to that?

My other question is this: On very long courses, say over 100 miles, which one is riding for time, essentially a TT, does one do better to climb a series of passes at the same HR or the same power? If one is riding for time, one gradually becomes more and more debilitated with each pass. Both my HR and power typically will drop on successive pass climbs, no matter how I eat and drink. It seems to me that holding back so I climb each pass at the same HR gives a slower result. I haven't tried climbing them at the same power.

Thanks.