2 years ago
03/21/2018 8:36am CDT
Lactate threshold, unfortunately, does not have just one feel.
One thing is for certain: It's harder "comfortably hard." For most people it feels pretty close to flat out. It's true that the first 20 minutes of a 1-hour race feel good, but that's when you're actually in a race. If you're doing a workout in the middle of the week, that usually feels really tough. In fact, the most common test that cyclists and triathletes use is a 30-minute flat out effort where the average power/pace/heart rate for the last 20 minutes is your threshold. The assumption underlying the test is that without real competition helping you to push yourself, you can only hold your 1-hour pace for half the time. (I think experienced athletes are much tougher than that, but it at least suggests that the pace isn't really very comfortable.)
Another thing to keep in mind is that many of the descriptions you're reading are talking about a certain level of fatigue. But fatigue increases throughout your run, even if blood lactate levels are at a steady state. So LT feels one way at ten minutes, and it feels different at 20. This is one of the shortcomings of the oxygen-centered model of fatigue. It doesn't really explain why we slow down at LT or slower paces, where oxygen shouldn't be a limiting factor and fuel definitely isn't.
One of the other big problems with trying to hit your LT pace in workouts, however, is that LT changes all the time. If you actually have a lactate analyzer and testing strips, you'll see that the very same pace, from day to day and week to week, will produce very different blood lactate levels. It's every bit as variable as heart rate. So you might have a finely tuned sense of "LT pace," but one week that might be 3 mmol, and another week it might be 5 mmol. And while it's true that in a week where your blood lactate is lower, every pace is going to feel easier, it isn't going to feel so easy that you can run for an hour at whatever faster pace is necessary that week to get to 4 mmol (I'm assuming for convenience's sake that your true LT is 4 mmol, even though it varies a lot). That's because there's more than your blood lactate level making it difficult to hold a particular pace. And, unfortunately, we don't know what all of those things are.
So here's my advice. Despite all these caveats, training at one-hour race pace is a useful weapon in your arsenal. It's the most important thing for half marathoners, it's very important for marathoners and 10k runners, and it's good early in the season for middle distance runners. You can learn what one-hour pace feels like by paying attention to how quickly your legs are moving. A "skilled" runner (not necessarily a fast runner) is one who can run specific paces at will. He knows the difference between a 75 and a 77 without looking at his watch. Some days 77 might feel as hard as 75, and on those days he might choose to change his workout, but still he knows exactly how fast his legs are moving because he can feel it, entirely apart from the subjective sense of effort. That's your sense of absolute pacing. The other skill that's important to develop is your sense of relative pacing. In other words, if someone tells you to run as fast as possible for X distance or Y time, you can set off at a pace that's pretty close to the maximum average pace you're capable of for that distance. That's how you figure out your LT pace for training purposes. Don't stress about whether you're running at exactly your LT; nobody even knows what their LT is (very few people are tested, and for those who do, standard lab protocols for LT testing have a uselessly large margin of error).
