Intensity Guidelines for 80/20 Running

by Matt Fitzgerald

Your 80/20 Run plan employs a five-zone intensity scale. It is very important that you do each workout and workout segment at the right intensity. This article provides all of the information you’ll need to determine your intensity zones so you can monitor your intensity during workouts and ensure you’re always in the right zone.

Your personal intensity zones can be automatically calculated based on the protocols below at the Zone Calculator. Beginner athletes may find the testing protocols outlined below difficult, so feel free to use Perceived Effort outlined at the end of this document until you are comfortable doing the testing below.

There is more than one way to measure intensity. I recommend that you use a combination of three intensity metrics: pace, heart rate, and perceived effort. Pace is useful because it’s a performance-relevant variable. You race on the clock, so why not also train by the clock? However, pace becomes less reliable when you’re running uphill or downhill.

Heart rate is helpful because it helps runners avoid the single most common training mistake: pushing too hard in runs that are supposed to be done at low intensity (Zones 1 and 2). 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 pace.

Perceived effort—or your subjective sense of how hard you are running—is important because it ultimately determines how fast you run in races. You may set and pursue time-based goals, but perceived effort has the final say in deciding whether you actually do maintain your goal pace or run faster or slower. However, perceived effort is poorly calibrated in many runners. In particular, most runners end up running at moderate intensity (in the gap between Zones 2 and 3) whenever they intend to run at low intensity if they go by feel.

It is because all three ways of measuring running intensity—pace, heart rate, and perceived effort—have pros and cons that I recommend using all three in training. Read on to find out how to determine your five training zones via each metric.

Note that pace applies to runs only, whereas heart rate and perceived effort can be used to measure intensity in cross-training workouts as well.

Run Pace 

Our training plans use a proprietary calculation for pace-based training zones. To determine your pace zones, visit the 80/20 Intensity Zone Calculator and enter a recent best performances for one of the distances listed. The performance does not have to be a race, but should reflect your current maximum capability whether it comes from competition or training or is simply an estimate of how fast you could run a given distance today.

A more accurate test is an actual 30-minute time trial. This is a brutal, but accurate method to establish your threshold pace. Warmup for 15 minutes with brief sprints of 10 seconds at estimated threshold pace. Then, perform a 30-minute time trial. Your average pace for that 30 minutes is your threshold pace.

Alternatively, you can also enter a known threshold pace from a previous testing protocol at the zone calculator.

Run Power

The protocol is similar finding your Run Pace. Warmup for 15 minutes with brief sprints of 10 seconds at estimated threshold power. Then, perform a 30-minute time trial. Your average power for that 30 minutes is your threshold power, or rFTP.

Our colleague Jim Vance has written another protocol to find your rFTP.


The simplest way to determine your five heart-rate based training zones is to back into them through pace. First, follow the guidelines under the Run Pace Section of this article and use the 80/20 Intensity Calculator to establish your run pace zones. In the results, note the pace that marks the bottom end (i.e., the fastest end) of Zone 3. This is your lactate threshold run pace.

The next step is to determine your lactate threshold heart rate. To do this, warm up with 10 minutes of easy jogging and then accelerate to your lactate threshold pace on a smooth, flat path or road. Wait for your heart rate to stop increasing and plateau. The number you see after it levels off is your lactate threshold heart rate. Now go to the Run and Cycling Heart Rate section of the 80/20 Intensity Calculator and enter your lactate threshold heart rate. Your five heart rate training zones will be calculated automatically.

Note that lactate threshold heart rate is slightly different in running than it is in other aerobic activities, so if you choose to cross-train, you’ll need to do separate tests in each of them. (Note that X and Y represent gaps between zones that are not targeted in workouts.)

Perceived Effort 

While I do not recommend that you use perceived effort as your primary intensity metric in training, it does have its place. Because perceived effort responds instantaneously to changes in intensity, it is a useful too for establishing the right intensity at the start of each workout segment, before you have a chance to capture a split time and before your heart rate has had a chance to adjust to the change of intensity.

Note, however, that perceived effort increases the longer you go at any intensity, so it is only useful for establishing initial intensity. For example, at the end of a very long run at a moderate pace, your perceived effort level may be “7” even though you are still in Zone2.

Use the guidelines in the following table to regulate your workout intensity by perceived effort. Note that these guidelines work in running as well as all possible cross-training activities.

Zone Initial Perceived Effort Rating on 1-10 Scale
1 1-2
2 3-4
3 5-6
4 7-8
5 9-10