Recently, low-intensity training, specifically training below the aerobic threshold, has continued to rise in popularity. How can you quickly and easily estimate your aerobic threshold, without needing to pay for an expensive laboratory visit?
Low intensity training is especially important for athletes & coaches who follow a polarized training approach. However, for athletes who want to incorporate more low-intensity riding into their training plans, it can be difficult to answer the question “how low do I need to ride?”
What is the ‘Aerobic’ Threshold & why is it important?
Many of us are familiar with the anaerobic threshold (AnT), which is often associated with Functional Threshold Power (FTP), Maximal Lactate Steady State (MLSS), or Critical Power (CP). Efforts above the anaerobic threshold can only be sustained for a relatively short duration until fatigue sets in. Although you might brag about your FTP to your buddies, it may not be the determining factor in winning longer, multi-hour events.
On the other hand, the aerobic threshold (AeT) is found at a much lower intensity, and it represents the transition from predominant aerobic towards an increasing reliance on anaerobic metabolism. At relatively low efforts, your body uses oxygen to power your efforts. As the demand for power increases, your aerobic system eventually maxes out – that is your AeT.
When riding above your AeT, aerobic metabolism cannot provide energy fast enough so the body starts to use carbohydrates via anaerobic glycolysis. This dependence on carbohydrates increases as you ride harder and harder. Further, since our bodies are only capable of storing a finite amount of carbohydrates, preserving that limited supply is crucial, especially for a long ride, a sportif, or an ultra/endurance race.
Therefore, your aerobic threshold has a vital role in training & racing, since it governs how hard you can ride for relatively long periods of time. If you are training for longer races or events, having a higher aerobic threshold usually translates into sustaining a higher speed/effort for those events.
How is Aerobic Threshold typically determined?
As noted above, your AeT signals the transition from aerobic metabolism to anaerobic glycolysis. Fortunately, the end product of anaerobic glycolysis – lactate – can be measured in a laboratory or with specialized equipment. At rest, and while riding below the AeT, blood lactate concentration remains relatively low. During the transition to anaerobic glycolysis, blood lactate levels begin to rise; this rise in blood lactate concentration above resting levels is considered the Aerobic Threshold.
By having athletes perform slow ramps (10-15 W increments every 3 min) and monitoring blood lactate levels at each stage, sports scientists can calculate the AeT. As your aerobic fitness increases, you would expect your power at aerobic threshold to increase.
For those of us that do not have access to a sports performance lab or a blood lactate monitor, how can we estimate AeT from your own basement or shed? Fortunately, there is a simple way to estimate the Aerobic Threshold from the comfort of your own pain cave.
The Talk Test
Believe it or not, we can use a verbal test in place of blood lactate measurements as a rough estimate of the AeT. This test is easier to complete indoors on your trainer, but could also be done out on the road. To perform the talk test, you’ll want to start by warming up at an easy intensity for 10-15 minutes before starting a slow, ramped effort. Unlike an FTP ramp test, this test will not push you to failure.
Start the ramp at a relatively low intensity (100 W, for example) and gradually increase the effort (~10-15 Watts every 2-3 minutes). In the last minute of each stage, try reciting the alphabet or reading aloud from a book. Ideally, you should be able to speak without gasping for air. Your aerobic threshold is the highest power (and heart rate) where you can continue to speak in phrases of about ~30 s. Once you find yourself gasping for air while speaking, you are above your aerobic threshold and you can stop the test. After completing your ride, you can review the data and make note of your Aerobic Threshold Power & Heart Rate.
For cyclists who follow a polarized training approach, knowing your aerobic threshold is vital, since endurance & recovery rides should be completed below your AeT. To do this, use the Power or Heart Rate from your talk test and use that as the upper limit for your endurance days. For example, if your AeT from the talk test was approximately 150 W, then you should limit your intensity on Endurance & recovery rides to no more than 150 W. These rides and intensities are also a great opportunity to build your respiratory capacity by breathing through your nose only.
Basically, you should be easily able to hold a conversation while riding. Personally, this means I can make my endurance & recovery rides more sociable by inviting friends to ride with me. Just remember to fight the temptation to make it competitive, sprinting for town signs, smashing Strava segments, etc.
For myself, a polarized training week typically looks something like this:
- Monday: High Intensity
- Tuesday: Recovery Ride < AeT
- Wednesday: Social Group Endurance Ride. Some intensity is permitted but overall keep things mellow
- Thursday: High Intensity
- Friday: Recovery Ride < AeT
- Saturday: Long Ride < AeT
- Sunday: Rest
In today’s article, we reviewed the aerobic threshold, which is where our body transition from aerobic to anaerobic metabolism. While typically determined in a sports science lab with blood lactate or respiratory data, we reviewed how you can determine your aerobic threshold at home using the talk test method. I hope you get a chance to test your aerobic threshold at home and utilize this information in your own training.
That’s all for this month! Stay safe, ride fast, and I will see you in the New Year.