Male Cyclist In Red Jersey Looks At The Trainingpeaks App On His Phone After A Fitness Test

Fitness Tests: Aerobic Capacity and VO2 Max

BY Maria Simone

Including fitness tests in your training regime can help you train smarter in the long run. Here’s how to regularly test and improve aerobic capacity and VO2 max.

Threshold testing gets a lot of attention, but it is not the only way to set your seasonal benchmarks. Regularly testing your progress across varying intensities — such as VO2 max and steady-state endurance — can allow you to identify and train your weaknesses, making you a better, more well-rounded athlete in the long run. Here are some easy ways to perform these fitness tests.

VO2 Max Testing

VO2 max is the maximum amount of oxygen you can use during intense training. Increasing your VO2 max translates to more oxygen consumption and, therefore, more energy production. 

Even if you don’t race at higher intensity levels, working to improve your VO2 max can bring you substantial benefits. In addition to improvements in energy production and delivery, a higher VO2 max can increase your lactate threshold, plasma volume, muscle strength, lactate tolerance, glycogen storage, and stroke volume. 

To get an initial read of your pace or power at VO2 max, complete a best sustainable effort session as outlined below:

  • Warm up for about 20 minutes. During this warm-up, be sure to include some short, harder efforts (around your threshold effort). For example, 5 x 1 minutes at threshold with 1-minute easy recoveries. 
  • Speed up to exert maximal effort for 5 minutes
  • Slow down for a 10- to 15-minute cool-down

After you’re finished with your session, take your average pace or power during the maximal effort portion of the workout to identify how quickly or powerfully you perform at your current VO2 max. You can easily do this in your TrainingPeaks app by identifying your peak 5-minute power or pace for the session. 

Below is an image of a peak 5-minute power portion of a VO2 max test I give my athletes. This particular workout was performed on Zwift. For analysis purposes, I find it easy to analyze and track this data from the web browser, but you can also see it in the mobile app. 

screenshot of a cycling workout with a peak 5-minute power portion of a fitness test

You can chart your peak 5-minute power over time on your dashboard, using the peak power or pace chart, shown below. As with above, the images below are from the browser version. 

VO2 Max Training

If part of your training objective is to increase your VO2 max, you’ll want to include VO2 max intervals into your training plan that target your corresponding pace/power numbers. One such session might include:

  • A 15-20 minute warm-up, increasing the intensity to around threshold effort periodically (between 30 seconds and one minute) 
  • 3-5 x 3 minutes at VO2 max effort (in other words, at the pace or power you identified above). For swimmers, this may be measured in terms of your 100-yard or 100-meter split pace. For cyclists, use power. For runners, use pace. Heart rate won’t be particularly useful for these intervals, as it is a lagging indicator and can take 1-3 minutes to fully register your effort. As such, your heart rate may not get into zone 5, but your pacing or power should. Your Rating of Perceived Exertion (RPE) for these efforts should be around a 9 — so very hard! 
  • 10-15 minutes of very easy cooling down 

Note: for sprint or draft legal cycling racers, you may also find value in tracking your 10-, 20-, 30-second, and 1-minute peak power. This is because you will often need to work at these efforts in order to stick with, or break away from the pack. Tracking your sprint power will help you understand your ability to achieve these goals. It can also give you a sense of your ability to maintain a sprint at the end of a race. 

These intervals will get easier as you continue your training protocol, indicating that your VO2 max is rising. Once you see a consistent change above a 5% increase from the original test, or a gradual decrease in RPE and HR for the same pace or power, it’s time to re-test using the same test as outlined above. Generally speaking, this can be done every four to six weeks when you are specifically working on VO2 max development. Use your updated pace/power numbers in your VO2 max intervals so that the intensity of the sessions keeps up with your current level of fitness.

Aerobic Fitness Tests and Progression

On the other side of the intensity spectrum, I also recommend benchmark and periodic assessments to get a sense of your aerobic fitness. As an endurance athlete, understanding your pace or power production at a moderate aerobic effort can give you insight into how your endurance is developing and can signal when it is time to change up your training to create new adaptations. 

When testing your aerobic fitness, you will want to make comparisons across the following metrics: 

  • Heart rate (HR) at 80-89% of threshold (commonly referred to as “zone 2” in many programs)
  • Power or Pace at an aerobic effort (HR as noted above)
  • Efficiency Factor (EF) is calculated for each workout you upload to TrainingPeaks that includes pace or power and heart rate. This number is a ratio of your heart rate to either normalized power (cycling or running) or normalized graded pace (running). This is a trend-based metric that can show improvement when making comparisons to similar workouts. See more in this article.
  • Aerobic Decoupling (Pa/Pw:HR) compares EF in the first half of a workout to the second half. When working out at a steady state, your heart rate will naturally rise over the course of a workout. If, however, your HR rises too high, or your pace/power drops too much for the same heart rate, this is an indication that you are not fit for the effort, fatigued, stressed, under-recovered, and/or dehydrated. This event is known as decoupling. A Pa/Pw:HR that is above 5% is generally considered decoupling. If you are finding that this number is regularly above 5% on steady-state aerobic efforts, you need to continue building your aerobic fitness. 
  • Variability Index (VI) is a measure of the smoothness or evenness of your power output. It is a calculation of the differential between your normalized power and your actual power output. Normalized power is an estimate of what your power would be if you applied an even force throughout the ride. Ideally, you want your VI to be at or near 1.05 for flat rides, and 1.1 for hilly rides. When doing intervals on the trainer, ideally similar efforts come in at or near 1.0.
  • Watts per kilogram (w/kg) is a measure of the power you produce per kilogram of body weight. It is a great basis for comparison between cyclists and can be particularly helpful for competition. For example, 200 watts for a 120-pound rider is a different effort than 200 pounds for a 150-pound rider. So, if you want to make comparisons to your competitors, watts/kilogram is the way to do it. For more information on watts/kilogram, see this article on why you should focus on this metric

As your aerobic fitness improves over time, you will see power osxr pace at a given HR increase. Alternatively, you may see HR decrease for the same power or pace. In either case, this is a good sign that it is time to re-test your threshold

Additionally, you will also likely see your EF rise as well. Once your EF plateaus for several weeks across similar duration and intensity, that is your signal to switch up your training stimulus. For example, if you’ve been riding regularly in the 90-120 minute range, on flat terrain, a plateauing EF may indicate that it is time to either increase the duration or change up the intensity (i.e., get in some more hills!). 

Aerobic Testing for Cyclists

If you’re a cyclist and want to identify the above data points, complete a 45- to 90-minute bike at mid-zone 2 HR (83-86% LTHR). The length of the ride will depend on your current fitness and race distance: longer course athletes should go to the 60-90 side of the spectrum, while shorter course athletes should do 45-75 minutes. If you are new to training, stick with the 45-minute option until you build up fitness. This session can be repeated every 4-6 weeks, making comparisons across the above data points. 

Aerobic Testing for Runners

For running, complete a 2- to 6-mile run at mid-zone 2 HR (83-85% LTHR). As with the cycling variant, select the duration that matches up with your focus as a short or long course athlete. Repeat the session every 4-6 weeks, making comparisons in pace, EF, and Pa:HR. If you run with power, you can also make comparisons on run power metrics.  

Aerobic Testing for Swimmers

For swimming, complete a 1,000 m continuous swim at an aerobic effort, which is about 10 seconds slower than your threshold swim speed (or RPE 4). If you’re a longer course athlete, you may go as far as 2,000 m. Note: your threshold swim speed is estimated as your best sustainable effort for 1,000 m or 3 x 300 m. For an aerobic effort, you can add 10 seconds to the average 100 m split. 

Regardless of the specific test, the principle remains the same: create the benchmark to get a sense of where you are today. Then, train to make fitness improvements in the specific area you seek, whether that’s threshold, VO2 max, endurance, etc. After several weeks, re-assess with the same testing protocol. Determine what has worked and what still requires additional attention. Review. Train again. Repeat.


Jewell, T. (2023, March 28). Everything to Know About VO₂ Max. Retrieved from

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About Maria Simone

Maria Simone is the owner and head coach of No Limits Endurance Coaching. She manages a staff of eight coaches and a team of 140 athletes. She is a USA Triathlon Level 2 long course, USA Cycling Level 2, and US Masters Swimming Level 1 certified coach. She was the 2021 Coach of the Year, awarded by Outspoken Women in Triathlon.

Maria offers mentoring for newer and intermediate coaches to support growth in coaching and business development. She takes a holistic approach to training that cultivates her athlete’s goals, physical ability and mental strength while managing a life-work-training balance. She is an active endurance athlete, enjoying long weekends in the pain cave, races with lots of hills, and hard runs through meandering singletrack trails with her husband John and her two dogs, Pace and Kea.

Visit Maria Simone's Coach Profile

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