Aerobic Threshold (AeT)

The aerobic threshold (AeT) is a measure of a trend change in your fatigue response as you increase your exercise level. We typically evaluate AeT during a graded or ramp exercise test (see CMP). AeT is considered the first threshold and is observed prior to the anerobic threshold and is a good description of your endurance platform and the intensity of exercise which marks a steady state and your highest level of fat oxidation. It can be identified by ventilatory or lactate trend changes where we see a slight change in your breathing and an associated difficulty in talking while exercising or at a one mmol increase in lactate levels in the blood. AeT is usually found around 65-75% of max heart rate for fitter individuals and 50-60% for the less fit individual.

The AeT heart rate and pace are used as an indicator of how well you have established your aerobic endurance. Since the AeT suggests for you an intensity level that is well enough below the lactate threshold that you are not producing metabolic fatigue and at a rate that would not generally overwhelm your aerobic system, but is still high enough to suggest maximum fat oxidation, it can be a good indicator of your aerobic foundation. 

If you know your AeT pace and heart rate then you can test and observe the coupling or de-coupling effect to evaluate where you are in your base development. To do this you will need to find a level course that will make it easy to maintain a consistent pace for walking, running or cycling. After warming up try to maintain your AeT pace for 20-50 minutes. This should be done during a longer workout and you will notice that after a while the heart rate begins to drift even though the pace remains the same (i.e., decoupling). Theoretically, when that pace and heart stay constant (less or no drift) and the data lines are parallel then your aerobic endurance is well established and you are ready to proceed to more intense building phases in your endurance training.

For a more detailed explanation of this decoupling effect and strategies read Joe Friels blog summary at http://home.trainingpeaks.com/articles/cycling/aerobic-endurance-and-decoupling,-by-joe-friel.aspx

During the CMP testing in our lab we identify your AeT and provide appropriate explanation for optimizing the training effect.

APPLICATION

For endurance athletes and enthusiasts the AeT is a good focal point for the long slow workout to optimize metabolic efficiency (better fat utilization) and prepare the musculoskeletal system for long efforts.  Most long course triathletes and ultra distance athletes will choose a race pace that is often quite close to the AeT.

All exercisers can benefit from some longer training that is at or near the AeT which will optimize endurance, promote better fuel utilization, burn calories, improve recovery capabilities, without overwhelming your energy and musculoskeletal systems.