MATT FITZGERALD – Runner’s Tribe

Matt Fitzgerald is an acclaimed endurance sports coach, nutritionist, and author. His many books include The Endurance Diet80/20 Running, and How Bad Do You Want It? 

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Lactate is having a moment. Our metabolite du jour owes its newfound celebrity largely to the hoopla surrounding the recent success of certain elite Norwegian endurance athletes, most notably triathlete Kristian Blummenfelt, who won the 2020 Tokyo Olympic Men’s Triathlon (held in 2021) and the 2021 Ironman World Championship (held in 2022), and who holds the world record for the Ironman 70.3 distance. Media stories about the success of Blummenfelt and his compatriots have homed in on their heavy reliance on blood lactate measurement in training, leading to a general impression among endurance athletes that this practice is the key (or at least a key) to their success, which in turn has caused my email inbox to be flooded by recreational endurance athletes asking me some version of the question, “Do I need to regularly measure my blood lactate in training to reach my full potential?”

I’ll attempt to answer this question by asking a different one: If Kristian Blummenfelt were somehow forbidden to ever again measure his blood lactate level, would he become less successful? Or better yet, If “Big Blu” had been prohibited from ever having his blood lactate measured from the very beginning of his career (he raced his first triathlon at thirteen), would he have been less successful to date? The answer to the former is almost certainly no. While I can’t speak for him, I’m confident that, after a moment of panic, Blummenfelt’s coach, Olav Aleksander Bu, would realize he could achieve the same end by different means, and in the long run the prohibition would prove to be little more than an inconvenience (not that blood lactate measurement is terribly convenient!). The two men have a system that clearly works, and lactate measurement is only a small part of it, and certainly not its essence.

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The second hypothetical is more speculative in nature, as it requires going back in time. Without question, lactate testing played an important role in the development of Blummenfelt’s winning formula, but was it essential? I doubt it. Lactate measurement might be having a moment, but there are plenty of champion endurance athletes who make little or no use of the practice. If lactate measurement were truly essential for endurance training optimization, East Africans, for example, would not dominate the sport of running as they do.

Don’t straw-man me here. I’m not suggesting that lactate measurement is useless. Taking up the practice could be transformative for many recreational endurance athletes whose training is currently all wrong. I just think there are other ways to obtain the benefits of lactate measurement, which are pretty basic: First, it helps athletes regulate the intensity of their training. Second, it helps athletes track changes in fitness.

Is it impossible to regulate intensity effectively or to track changes in fitness reliably without taking lactate measurements? Some people seem to think so, but I sure don’t. For example, some coaches like to use lactate measurements between during recovery periods in interval workouts to determine when the athlete should stop. (There’s nothing new about this practice, by the way—I remember Tom Craig employing it with Regina Jacobs in the 1990s.) Instead of trying to guess ahead of time how many intervals will maximize the workout’s intended purpose without overtaxing the athlete, these coaches just have the athlete keep going until their blood lactate level says they’ve had enough. That’s pretty neat, but any suggestion that there’s no other way to dose interval work optimally is poppycock.

Not to toot my own horn, but I’m pretty confident that the majority of interval workouts my athletes perform are neither too easy nor too hard. Simply knowing my athletes enables me to design workouts that are close to the Goldilocks Zone. The athlete then does the rest by understanding the purpose of the workout and fine-tuning the session as they go to ensure optimal execution. If lactate measurements were taken throughout every interval workout done by every athlete I coach, it would appear as if they were all planned around lactate. That’s because there are consistent mathematical relationships between blood lactate and things like breathing rate, time spent at a given power output, and perceived effort, making it possible to design and execute very precise training stimuli without reference to lactate.

Indeed, in an article on lactate training that got a lot of attention recently, former elite Norwegian runner Marius Bakken mentions that when he started taking lactate measurements on his Kenyan training partners, he found that they were doing a better job than his fellow Norwegians of hitting lactate targets—without actually targeting them! That kind of says it all right there.

In a certain sense, the argument that lactate measurement is essential to optimizing endurance fitness is akin to the argument (which nobody makes) that brain imaging is essential to optimizing learning. Although it is true that learning cannot occur unless the brain of the learner is changed in particular ways, the real point of learning is to make use of what is learned, and the best proof of learning is its practical use. Similarly, although endurance athletes cannot optimize their fitness without changing their lactate dynamics, the real point of training is to improve performance, and the best proof of performance is performance. If teachers and coaches respectively simply focus on improving what students and athletes can do, they can trust that their brains and bodies are changing in the necessary ways.

Again, though, I’m not pooh-poohing lactate measurement. To close with another hypothetical, if it somehow came about that I was required to conduct regular lactate testing with every athletes I coach, I have no doubt that certain of my decisions would be influenced by these measurements in ways I didn’t later regret. But the same can be said of virtually any source of valid data with known relevance to intensity and fitness, such as run power, which wasn’t a thing when I started coaching but is now something I use with a lot of runners and triathletes (without regarding it as essential, either).