When talking about speed workouts, we’ll often mention different race paces — speeds that you can sustain over a 5K, 10K, half marathon, and so on. What we’re really talking about is your lactate threshold, and as you get deeper into running, it becomes more important to understand. And no, it’s not how much milk you can drink! Your lactate threshold is the intensity level of a workout that is difficult but sustainable, and there are a ton of benefits to understanding where that level is for you.
The lactate threshold is based on the main antagonist to high intensity running — lactic acid. For most people, lactic acid is the sour part of sour milk products, but for us runners, it’s a byproduct from the breakdown of carbohydrates. While it’s produced during most kinds of exercise, runners will find it most apparent during higher-intensity workouts because the acid builds up in the bloodstream faster than the body is able to get rid of it. If you’ve ever gotten a slightly acidic taste in your mouth along with nausea and muscle fatigue while running, you know what I’m talking about. It’s something to avoid if we can help it, and that’s where the lactate threshold comes in handy.
Lactate threshold is the intensity level past which the concentration of lactic acid in the bloodstream will increase because it’s entering the body faster than the body can remove it. Knowing where this threshold is helps us avoid the uncomfortable feeling that comes along with lactic acid buildup, but it also lets us know the level that we can push ourselves to on race day without prematurely crashing and burning.
The big question that you’re probably asking (and the one that runners have been trying to answer for years) is how do I find my lactate threshold? It’s not exactly as straightforward to find as we’d like. There are doctors and machines that can measure your lactic threshold, but the result is a number that most of us don’t know how to use.
In the age of fitness tracking, there are other measures we can use in a pinch. Some heart rate monitors give you a threshold heart rate range that you can use to maintain a safe and sustainable pace, making it a decent stand-in for the lactate threshold. The most accurate method is to simply do longer speed workouts to see what kind of pace and intensity you can sustain. If you go this route, fitness tracking or keeping a log is crucial.
Finding your lactate threshold is just the first half of the battle. During training runs, we’re trying to prepare for success, whether that be in future workouts or on race day. The best way to prepare is to spend time running at your target pace during workouts. Some say practice makes perfect, but I like to think that practice makes permanent — what we do in practice is the way we’re most likely to perform at the end of the day. The more time we spend running at our lactate threshold, the more accustomed our body becomes to this intensity and the stresses that come along with it.
In practice, lactate threshold is more important to speed workouts that use longer intervals, with the shorter workouts requiring us to push past the lactate threshold and get a little uncomfortable. You’ll want to consider your lactate threshold when using Fartlek training and tempo runs rather than track workouts or hill repeats. While using and identifying lactate threshold is always a work in progress, being able to use it will make it your best friend when preparing yourself for race success!
