Intensity Guidelines for Cycling

Intensity Guidelines for Cycling

We recommend that you also read Understanding Your 80/20 Cycling Plan and Understanding Your TrainingPeaks Structured Workout Plan


Your 80/20 Cycling Plan employs a proprietary seven-zone intensity scale. Performing each workout and workout segment at the right intensity is at the heart of 80/20 training. This article provides all of the information you’ll need to determine your personal threshold and intensity zones so you can monitor your intensity during workouts and ensure you’re always in the right zone.


Determining your intensity zones is a three-step process. Step one is to choose a preferred way of measuring intensity. Step two is to perform a field test to assess your threshold. Step three is to calculate your personal zones from that threshold with the help of our zone calculators.

Step 1 – Choose Your Preferred Intensity Metric

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There are two ways to measure cycling intensity: power and heart rate. The testing protocols for both metrics are described below. Each metric has advantages and disadvantages relative to the others:


Power is the most versatile way to monitor cycling intensity. As a pure measure of your work output, power is the same in all conditions, requiring fewer conditional adjustments than pace and heart rate. Less familiar than the other intensity metrics, though, power-based training takes some getting used to.

Heart rate has the advantage of reflecting physiological intensity, or how hard your body is working, unlike pace and power. But heart rate is not a reliable way to monitor intensity during short efforts at high intensity because heart rate lags behind abrupt changes in output. Heart rate is also influenced by environmental and other factors, including temperature and hydration status, that can distort its relationship to actual exercise intensity.

Step 2 – Perform a Field Test to Assess Your Threshold

Once you have chosen a method of monitoring intensity in your 80/20 Cycling Plan (and you may use more than one), you need establish a personal threshold for that specific metric through field testing. Threshold is unique to each individual cyclist and evolve over time with changes in fitness. A number of different field tests have been scientifically vetted and shown to accurately measure your current cycling threshold.

Power Testing

The most straightforward field test to find threshold power is a 20-minute time trial. Begin with a warm-up that consists of 15 minutes of easy spinning with a few 15-second surges at the effort you intend to maintain for the time trial. Next, cover as much distance as you can (real distance if you’re outdoors, virtual distance if you’re indoors) in 20 minutes, being careful to avoid starting at an intensity that’s too fast to sustain and thus slowing down involuntarily near the end. Your functional threshold power, or FTP, is equal to 95 percent of your average power over the full 20-minute time trial, which can be entered into the 80/20 Zone Calculator.


If you already know your cycling lactate threshold heart rate (LTHR), you can use it to find your rFTP with a short field test. After warming up, play with your power until your heart rate settles in at your previously established LTHR for 10 minutes. Your power at this heart rate is close to your FTP.

Heart Rate Testing

The simplest way to determine your heart rate threshold is to back into them through power. First, follow the guidelines under the Power Testing section of this article to establish your FTP.


The next step is to determine your Lactate Threshold Heart Rate (LTHR) from your FTP. To do this, warm up with 10 minutes of easy spinning and then accelerate to your FTP. Wait for your heart rate to stop increasing and plateau. The number you see after it levels off is your LTHR. Now go to the Run and Cycling Heart Rate section of the 80/20 Zone Calculator and enter your lactate Threshold Heart Rate. Your seven heart rate training zones will be calculated automatically.


If you have not yet established your FTP, you can find your LTHR independently through a time trial. Begin with a warm-up that consists of 15 minutes of easy spinning with a few 15-second surges at the intensity you intend to target for the time trial. Next, increase your effort to the highest level you feel you can sustain for 20 minutes and hit the lap button on your heart rate monitor watch. Five minutes into the test, hit your lap button again. Fifteen minutes later, at the end of the 20-minute time-trial, hit the lap button again or end the time trial. Your LTHR is your peak 15-minute average within that 20-minutes test (the average heart rate in beats per minute (BPM) of the final 15 minutes of the 20-minute test).


Note that Lactate Threshold Heart Rate is slightly different in cycling than it is in other aerobic activities, so if you choose to cross-train, you’ll need to do separate tests in each activity.


Also note that heart rate is significantly influenced by factors such as temperature, humidity, sleep, stress, time of day, and even when you last ate. Therefore, your Lactate Threshold Heart Rate test result is specific to the environment and conditions in which you test. For example, an LTHR test indoors in February in the morning will not be the same as an LTHR test in July outdoors in the afternoon. Perform your LTHR in the environment that most accurately represents where you will do the bulk of your training.


For various reasons, most athletes find that their threshold is 5-10 bpm lower indoors than outdoors. For this reason, it may be practical to maintain separate indoor and outdoor HR zones. Or simply adjust your zones appropriately when moving between outdoor and indoor environments.

Simultaneous Threshold Testing

Because the 20-minute test protocol is the same for power and heart rate, you have the opportunity to capture both intensity types within the same test.

Step 3 – Calculate Your Zones

Once you have a result from your chosen field test, go to the intensity calculator and enter it in the appropriate field. If you wish to have your zones automatically sent to your your 80/20 workouts on TrainingPeaks, follow the steps outlined in the document Understanding Your Structured Workout Plan.

Keeping Your Zones Current

As your fitness level changes, you will need to adjust your zones to keep them current. Many athletes like to update their zones on a regular schedule. If you wish to do so, choose a preferred testing method and repeat it during every second recovery week beginning with the first recovery week of your plan. Note that recovery weeks fall every third week in all of our cycling plans. Thus, if you elect to perform scheduled testing, you will test in Week 6, Week 12, etc. some but not all of our Cycling Plans include scheduled threshold tests in these weeks. If your plan doesn’t include scheduled threshold tests and you want to insert them, the least disruptive way to do so is to perform them in place of the most challenging workout of the relevant week that features efforts in Zone 3 or higher.


Also note that if you are an intermediate- or advanced-level cyclist and you use heart rate as your primary intensity metric, you probably don’t need to update your zones very often. This is because LTHR doesn’t change a lot with changes in fitness once you’re past the beginner (or starting-over) phase. What you will find as you gain fitness is that you produce more power at the same heart rates. Indeed, one simple way to update your pace or power zones is to do a test where you ride at your current known LTHR and identify the corresponding power, then plug this number into the appropriate calculator. For example, if you know that your LTHR is consistently stable at 160 BPM but you notice that you’re producing more watts at any given HR lately, do a ride where you lock into a heart rate of 160 BPM and note the corresponding power. Say your power is 250 watts at this HR. This, then, is your approximate FTP. It’s best to do this particular test within the context of a scheduled ride that targets Zone 3.