The 30-Minute LTHR Test
I love working with athletes. I really do. For the most part they are healthy, happy, motivated, and driven to succeed. Helping athletes learn more about training and racing is great fun. But on occasion I run up against something that seems simple, yet many can’t quite seem to grasp. This is the case with the 30-minute test for lactate threshold heart rate (LTHR). Basically, the test is just to go as hard as you can for 30 minutes and then your average heart rate for the last 20 minutes is close to your LTHR.
It seems so simple, and yet I get comments from readers indicating they are confused. Nothing in the years I’ve been coaching has been so hard to get people to understand. But I think I’ve just figured out why that may be so.
Distance vs. Time
It has to do with the mindset endurance athletes have. Athletes race a given distance—not a given time. So if I told a group of runners to go out and run 8km as fast as they could, there would be no confusion. If I told a bunch of cyclists or triathletes to do a ride of 20km at an all-out effort, they’d be all over it. But if I tell these same groups to run or ride as fast as they can for 30 minutes, many, if not most, are confused.
I’m beginning to understand that those who are confused about the 30-minute test don’t seem to understand how to pace themselves for a given amount of time—only for a given distance. Why that is the case I don’t know. If you typically complete a 20km time trial on a bike in about 30 minutes then you know how to pace yourself for about 30 minutes (or whatever your race time would be). If you normally run 8km in about 30 minutes then you know how to pace yourself for 30 minutes.
So if you are in a fog about the 30-minute test, do this: Determine how much distance you could cover in 30 minutes at race effort/pace and go do a solo time trial over that distance. It would be just like a race. And all endurance athletes know how to do a race. Simple solution.
A Few Notes on Your LTHR Test
Realize that you won’t be quite as fast for a solo “race” as you would for a real race. In fact, you’ll probably be about 5% slower when doing it by yourself. We tend to feel sorry for ourselves when alone and much less so when in a real race.
If you insist on using a real race for this test of LTHR, then the race distance needs to be long enough to require you take an hour to finish it at an all-out, race effort.
Realize that LTHR varies by sport, so if you are a triathlete you have to do it for both cycling and running with separate tests. You should be rested before the test. Your average heart rate for the last 20 minutes of your “race” time is an approximation of your LTHR.
LTHR, Power, and Pace Changes
In a related matter, a reader asked in a recent comment how often I find that LTHR changes during a season. Hardly at all. Once an athletes is in decent condition, it is quite stable. What changes is how fast or powerful you are at that heart rate. So I have athletes do the 30-minute test about every 4 to 8 weeks—not to find their LTHRs, but rather their functional threshold power or pace (FTP). Basically, I’m just confirming LTHR. It will vary a few beats per minute from one test to the next, but that is usually insignificant. Power and pace is what we really want to see change. You won’t go faster because your heart rate is higher but rather because your pace is greater or you are more powerful (they are actually the same thing—even runners produce power—but let’s not make things even more confusing).
Heart rate doesn’t determine the outcome of a race—power and pace do. There are no podium positions for high heart rates. So I want to confirm fairly often with the athletes I coach that we are making gains in the “output” aspect of lactate threshold. Heart rate is the “input” aspect of LT. One of the simplest ways and yet also one of the most precise for determining fitness gain is to see how much output you get for a given input. The greater the output-input ratio, the more fit you are for endurance sport.
[Related: “Determining Your LTHR“]