What Is the Anaerobic Threshold?

By Jean D , last updated November 18, 2011

Spend any time listening to professional runners swapping training tips and you may emerge wondering, "What in the world is the anaerobic threshold?" The anaerobic threshold, or AT for short, is a method professionals use to train at maximum capacity and improve their performance. Athletes jealously guard their AT, keeping the number in mind as they work out and trying hard to improve their score. While you may not be a professional athlete yourself, knowing what anaerobic threshold means, and figuring out how to apply it in your own workouts, could help you improve in your sport in a short period of time.

A Definition for Rookies

Doctors and physiologists can explain the anaerobic threshold in incredibly precise terms, but there is a quick way to explain anaerobic threshold, using running as an example. When you're running, you're breathing hard and you're supplying your muscles with oxygen and energy. The muscles create toxins as they break down this oxygen and energy, but those toxins are quickly dispersed and they don't build up. This is an aerobic system. Over time, if you're running quite far and you're running quite hard, your body can't pull in enough oxygen to meet demand. You're still running and you're still putting a heavy workload on your muscles, but you're not supplying them with the energy and oxygen they need to use the aerobic system. The muscles then begin to burn up their own stores of energy, and they build up an increased amount of toxins that aren't being removed in the system. This is an anaerobic system. When you move from the aerobic system to the anaerobic system, you've crossed the anaerobic threshold.

Why it Matters

When you're in the anaerobic system, different muscle types are firing and toxins are building up. You might cycle between aerobic and anaerobic systems, but you can't clear that backlog of toxins in a few moments. Your muscles become weak and they can feel like they're burning. Some people even report that their muscles simply give out and don't want to work anymore. If you have a low anaerobic threshold, this could mean that your muscles give out early in the race. People with low anaerobic thresholds may not be able to compete effectively.

Training around your anaerobic threshold could help you build up endurance and do more in the aerobic part of the cycle, so you could compete at a high level for a longer period of time before you begin to build toxins in your system. You'll push quite hard, hit the threshold, and exercise just beneath this threshold.


Professionals often rely on expensive blood tests that measure blood toxins. If you're running just for a hobby, you may not need to get this precise in your measurements. Instead, think about exercising to the point when you are sweating and exerting yourself, but you can still talk comfortably. This is your anaerobic threshold, or quite close to it, and you should exercise at this level at all times to maximize your workouts.

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