A lesson I have had to learn the hard way—and one I try to instill in my athletes so they don’t make the same mistakes—is that running as fast as you can for as long as you can every day rarely leads to personal bests. Instead it often leads to injury and overtraining.
Racing and racing fast means running smart and targeting workouts at precise efforts that reap specific benefits. Yes, that means the slow, easy run is just as critical to running fast and training well.
Most runners have heard the term “tempo run” before. Still, many don’t realize that there are three different types of tempo runs. Understanding the precise differences between the three is critical in targeting the right effort levels.
With terms like “lactate threshold,” “tempo run,” and “anaerobic” being thrown around interchangeably, understanding your training can get pretty confusing. It can complicate figuring out your tempo run pace. Here is how to differentiate between the different tempo efforts and what they are meant to accomplish.
1. Anaerobic Threshold
The word anaerobic means “without oxygen.” In the world of exercise science, it describes strength-building exercises in contrast to longer endurance training. When a long-distance runner performs an anaerobic threshold workout correctly, their body is producing lactic acid slightly faster than it can be cleared from the bloodstream.
When lactic acid cannot be cleared from your muscles more quickly than produced, it creates a burning sensation in the legs, signaling that you are running right on the edge of your anaerobic threshold.
Increasing your anaerobic threshold is essential for runners who are racing all distances because it allows the body to run faster before fatigue and lactic acid take over. It should be an effort that you could hold to failure for about one hour, but when performing an anaerobic threshold workout, intervals should last eight to twelve minutes.
Often, when an athlete feels good and wants to run faster on a day that is designated to tempo effort, they do so at a pace that does not increase the anaerobic threshold too much. By running more quickly, they are actually hurting their ability to race faster in the long run.
2. Lactate Threshold
As you run faster and faster, your body uses less of your aerobic system and more of your anaerobic system which produces energy through glycolysis—essentially, the fermenting of the muscles that create the byproduct of lactic acid.
While anaerobic and lactate thresholds are similar efforts, they should not be interchangeable. The lactate threshold is the point at which lactic acid is just beginning to accumulate. In contrast, the anaerobic threshold describes the point at which lactic acid builds faster than the body can remove it.
Lactate threshold efforts are slightly slower than the workouts that target the anaerobic threshold and should feel somewhat easier on shorter periods and can be extended slightly on longer repeats.
The effort for lactate threshold workouts usually corresponds to a 10 mile or half marathon race. Runners can hold their lactate threshold pace for 20-40 minutes in training, depending on how fit they are and the exact pace they are running.
3. Aerobic Threshold
The word aerobic means “with or involving oxygen.” A runner’s aerobic system uses oxygen and burns fats, proteins, and carbohydrates. It is the primary energy system used in long-distance running.
Unlike the anaerobic system, the aerobic system produces energy slowly, so it cannot be relied upon immediately when large amounts of energy are needed. The aerobic threshold is the level of exercise intensity at which an athlete can run without accumulating significant lactic acid.
For most runners, this is roughly a current marathon race effort, not to be confused with goal marathon race effort.
The higher your aerobic threshold, the faster and longer you can run before crossing the line into anaerobic metabolism. For marathoners specifically, the aerobic threshold is the fastest pace at which you can still burn fat efficiently as a fuel source.
Workouts that focus on endurance and stamina rather than short bursts of speed are the kind of workouts that benefit the aerobic system. A dependable threshold workout is the “steady-state workout.” Generally, steady-state workouts are performed at about 10 seconds faster to 20 seconds slower than the current marathon pace for four-eight miles depending on fitness.
Now that you know the lingo, slow down on the sprinting and work on that endurance.