What is an Anaerobic Threshold?

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  • Written By: Josie Myers
  • Edited By: Bronwyn Harris
  • Last Modified Date: 28 February 2020
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A person's anaerobic threshold has been reached when their body is under extreme conditions and the burning of oxygen can not keep up with the body's demands. At this point, the body begins to burn stored fuels, like sugars, instead of oxygen as the primary fuel. The word anaerobic literally means "without oxygen." This threshold can be expanded by training, so athletes are most often concerned with where this threshold is and how to expand it.

When the body is under regular conditions, it burns oxygen as the primary fuel to continue motion. This kind of activity is called aerobic. Carbon dioxide is produced as a byproduct of the process and is expelled through the lungs. The aerobic system is active for most daily tasks and light exercise.

When a person demands more from their body than the aerobic system can keep up with, the body switches to the anaerobic system to burn fuels in order to keep the body in motion. This anaerobic threshold is reached after long periods of activity or during a quick burst of activity such as a runner's sprint. The primary difference between the aerobic and anaerobic systems is in the byproduct produced. The aerobic byproduct, carbon dioxide, can be easily expelled by regular breathing, while the anaerobic byproduct is lactic acid. This lactic acid build up in the muscles quickly and causes fatigue.


Many athletes are interested in learning how to expand their anaerobic threshold in order to work longer and more efficiently. It is possible to train the body to have a higher threshold. Repeated training near the threshold will increase the body's efficiency at burning oxygen and therefore increase the threshold.

In order to expand the anaerobic threshold, it is important to discover exactly where it is for each individual. Doctors can discover the exact threshold through blood testing during physical exertion tests, since lactic acid will be evident in the blood. Smaller versions of the laboratory equipment used by doctors are available for coaches and trainers to carry for periodic testing of their athletes.

Some choose to estimate the anaerobic threshold by finding the heart rate. To the best of scientific knowledge, the threshold occurs between 85-90% of the maximum heart rate. To determine the maximum heart rate, take 220 and subtract the age of the athlete, then multiply the result by 0.85 and 0.90. For a 31 year old, the maximum heart rate would be 189 beats per minute, with the threshold kicking in between 160 and 170 beats per minute. This method is the least accurate, but can provide some idea of where to aim for someone not willing to go through clinical testing.


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Post 2

@Subway11 - I agree with you. I really am not at the point that I can do anaerobic exercise but it is something that I am shooting for. What I used to do is jog at a 6 miles per hour pace for thirty minutes, but after a while I did not see any gains and then I started doing intervals at varying speeds for a minute or two and I really noticed a difference.

I start at 5.0 miles per hour and then jog at that pace for a minute before I go to 5.5 miles per hour and work my way up to 8.0 miles per hour. I then do a two minute recovery interval

at 4.5 miles per hour before I repeat the pattern.

I usually repeat the pattern about three times, but in the article that I saw in a fitness magazine they suggest repeating the pattern five times. I am not there yet, but I do like the results that I am seeing so far. Jogging is becoming easier and my body is becoming leaner. I really am enjoying my workouts more too.

Post 1

I heard that anaerobic threshold training is important to raise your fitness level and overall endurance. I have tried to do some shorter sprints for about one to two minutes going at a speed of 8.5 miles per hour, but I usually can’t run longer at that speed because I just lose my breath.

I try to do a recovery jog of about 2 minutes at about 4.5 miles per hour and then I raise the speed again. I would love to get to the point where I can run about nine or ten miles per hour for at least five minutes. The more I try to challenge myself like this the more calories I burn too.

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