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If you've been a part of this sport for any length of time, you've heard about heart rate monitors, power meters, training zones, etc. You've probably also heard about different testing methods to help athletes and coaches better use these devices to enhance training and performance. One of these tests is called a "lactate threshold" test. You don't hear a lot about triathletes using this type of test, but of course Craig Alexander, defending champion at the Ironman World Championships, wants every advantage he can get. He has been working with Mat Steinmetz of Retul to track what's called his "blood lactate curve" to make sure his training is right on target for a third straight victory at Kona. To understand what this test is, we have to first take a basic look at how athletes train with power.
With the introduction of power meters, athletes have been able to accurately measure the amount of power they are using to pedal a bicycle. This is measured in watts. Athletes monitor their power levels to track their progress in training, and also to determine what workloads they should use during training and racing. "Functional Threshold Power," or FTP, is generally used by convention to refer to the power that an athlete can hold for approximately one hour before becoming exhausted. From there, athletes and coaches can plan workouts, race plans, and long-term goals.
For example, if an athlete has an FTP of 300 watts, they wouldn't want to push 300 watts during any triathlon lasting more than an hour. Doing so would lead to a pretty hard burnout at the end of the run. For an Olympic-distance triathlon, it might be prudent to pedal at 85-95% of FTP (roughly 255-285 watts). That will help the athlete to push hard enough on the bike while still conserving enough energy to put together a solid run. For an Ironman-distance race, it would be better to use less power still, since the race is so much longer. Somewhere between 65-75% of FTP might be more appropriate (perhaps more or less, depending on fitness).
But what percentage is optimal? This is where it gets tricky. FTP is also referred to as "Onset of Blood Lactate Accumulation" or OBLA. While these two terms don't necessarily have the same definition, they are widely seen as the same thing in practice. Lactate is a word you've probably heard thrown around a lot. We turned to Mat Steinmetz for a formal definition. In Mat's words, "lactate is a byproduct of glycolosis, or carbohydrate metabolism, and is produced when the body is unable to supply all of its energy needs aerobically. There are three critical markers, shifts in the lactate curve, which are used to monitor or alter an athlete's training program."
Pedaling at FTP for roughly an hour is the point at which your body can no longer supply your energy aerobically, and begins to dump lactate into your blood. This is going to make you exhausted, make your muscles stiff, and make you unable to continue. The ranges of work described above for triathlon racing make certain assumptions about how your body will handle lactate at levels below FTP. To make those ranges, certain assumptions are made about how the majority of athletes will respond at 60%, 70%, or 80% of FTP. But the important part of the story is that every person responds differently.
And that's what LT testing is all about. By sampling blood during exercise at increasingly large loads, the tester is able to plot a curve of lactate accumulation over a range of loads. Essentially, the curve will show the athlete how good they are at managing lactate levels at various workloads.
That's exactly what Craig Alexander and Mat Steinmetz have been doing this season to perfect Craig's form. Earlier in the year, he was focused squarely on Half-Ironman events, and was racing at a power level closer to his FTP. Accordingly, it wasn't quite as important to keep lactate at bay when he was pedaling at, say, 70% of his FTP. It was more important what happened when he pushed it to more like 80-85%, or thereabouts. But with Kona on the horizon, his training focus has switched. Now, he doesn't need to worry about what's happening when he's at those much higher power levels. He wants to be able to push his mid-range power for longer without building up much lactate, keeping his legs fresh for that blazing run speed of his. Knowing his own lactate curve, and how it has changed, essentially gives Alexander a report on how well his training has paid off. It is a key to checking his fitness level, and will determine whether any aspect of his training needs to be tweaked going into the last few weeks before the race. If he pulls off the win this year, he will join Dave Scott and Mark Allen by becoming only the third man in history to take three consecutive titles.