Thinking More in Depth About Lactate Threshold Training
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When training the distance runner, many folks agree it’s hard to find more bang for your back than running workouts focusing on improving one’s lactate threshold. There is a certain pace a runner can run where she is able to clear lactate at the same rate the body is producing it and faster than that pace results in the accumulation of lactate in the blood. Lactate is not necessarily a bad thing, but it is easily measure and increases proportionally with things that do cause a runner to slow down.
Jack Daniels says it is often best to think of the purpose of threshold runs as “improving your endurance — teaching your body body how to deal with a slightly more demanding pace for a prolonged period of time, or increasing the duration of time you can hold at a specific pace.” He goes on to say, “threshold runs improve the speed you can keep up for a relatively long time.” Bob Larsen, longtime coach of Meb Keflezighi, is well known for saying, “When in doubt, do a threshold workout.” There is tremendous value in improving your lactate threshold and it’s hard to find workouts that offer a bigger return when thinking about improving as a distance runner.
From what I’ve seen, coaches at different levels progress threshold workouts in different ways. You often see shorter cruise intervals progressing towards straight tempo runs in the neighborhood of 20–20 mins. Other coaches go back and forth between straight threshold runs and cruise intervals, and others use other methods such as wave tempos or alternations to achieve a similar effect. Despite it being such a valued method of training, I’ve seen little written about how to think about the effects one type of threshold workout has compared to another.
When I saw Marcus O’Sullivan present at the Day of Distance Coaching Clinic, he introduced the idea of “Threshold Production Time” when thinking about cruise intervals. To summarize his hypothesis (using roughly a 5:1 work to rest ratio when thinking about cruise intervals) he believes the first 45 seconds or so of each repetition are spent getting the time where you are actually stressing your lactate threshold. So for example in a workout that is 10 x 3 mins @ LT w/ ~45 seconds rest, each rep has about 2:15 of time where the workout is in the desired adaption zone. So even though you are running 30 mins of “work,” 22:30 is the time of the workout that is at the level of the adaptation you are seeking (2:15 x 10).
Compare the 10 x 3 mins workout to 5 x 6 mins with 60–75 seconds rest and you’ll see that roughly 5:15 of each rep is at the desired level of adaptation. So in 30 minutes of “work” in this case, 26:15 (5:15 x 6) is at the desired level of adaptation, or nearly 4 minutes more than the 10 x 3 minute workout. He expressed this idea through “Total Production Percentage,” listing the 10 x 3 mins as having 75% Total Production (22:30/30:00) vs. 87% for the 5 x 6 mins (26:15/30:00).
I don’t think it’s quite as precise as that, but I think it is an interesting model that raises some interesting questions. While it probably takes longer than 45 seconds to reach the threshold level in the early intervals, it probably takes less in later repetitions. What I am curious about is can you make the claim that a 10 x 3 minutes workout has a very similar effect to a ~24 minute straight tempo run accounting for ~90 seconds to get to the lactate threshold training zone? If so, 10 x 3 minutes seems to be a much more doable workout for most folks. I understand there is an element to training the mental side of running that a straight tempo teaches, but under this model cruise intervals or broken threshold seem to have a pretty good bang for their buck in accumulating time at threshold.
Does that mean the if you were the keep the recovery portions steady, it would result in a higher total production percentage for the same amount of work? When thinking about a standard Kenyan Fartlek of 20 x 1 minute on with 1 minute steady, do you get a very high production percentage in those 20 minutes of “on” running do it taking very little time to get to the threshold level? Would that type of running be even more effective if you ran a mile at threshold first to increase blood lactate to the threshold before starting the fartlek?
I certainly do not have all of the answers, but this was the first time I’ve seen a breakdown of cruise intervals in a way that quantified what was happening. It will continue to make me think about the best ways to use this work in training moving forward.
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