Intensity Zones and Interpreting Workouts

A well-structured training plan requires that you maintain specific intensities for specific durations.  When reading your workouts within TrainingPeaks, you will see  shorthands and references to various Zones, which refer to the level of intensity you should be exerting at any given time within a workout.

For our purposes, there will be five intensity zones, with Zone 1 being the easiest and Zone 5 being an effort near your VO2 max. These five zones key off of a metric such as heart rate, measured in beats per minute (BPM) or some pace/power that you determine via a field test or race.  If you do not know or cannot measure specific heart rate or pace/power metrics, you can also key off of a level of perceived exertion on a 1-10 scale, often referred to as rated perceived exertion (RPE), with 1-2 being extremely easy, 3-4 being easy, 5-6 being moderate to somewhat hard, 7-8 being moderately hard, and 9-10 being hard (race pace for events lasting ~8-15 minutes).  

Many plans prescribe intensities off of a percentage of max heart rate.  Although this can work, it is extremely difficult and exhausting to measure max heart rate and the common formula (i.e., 220 minus your age) is largely worthless as there is tremendous variation between and among individuals.  For these reasons, to establish your intensity zones we will perform “threshold field tests” and monitor your heart rate and pace/power during these tests in order to establish a threshold heart rate (THR), functional threshold power (FTP) and/or threshold pace.  These threshold efforts are smack dab in the middle of Zone 4 and the other zones are stipulated as a percentage of them.  For example, Zone 2 on the bike is stipulated as 69-83% of your cycling threshold heart rate and Zone 2 on the swim is your threshold pace plus 10 seconds.  Below is a chart summarizing the intensity zones for each the swim, bike and run.  You can also click the "Intensity Zones PDF" link to download a PDF of the chart.

 Intensity Zones PDF


Screenshot 2018-01-01 12.56.19.png


Understanding and Interpreting Workouts

Spending time in each intensity zone leads to certain physiological adaptations unique to that zone with workouts structured accordingly.  Zone 4 and 5 efforts are fairly intense and are generally broken down into intervals.  For example, if a session stipulates “5x4 minute Zone 5 intervals with three-minute Zone 1-2 recoveries,” it is directing you to perform five intervals of four minutes each at a Zone 5 effort, with each interval separated by an easy three-minute Zone 1-2 rest/recovery effort.  Lower-intensity workouts, such as those that focus on Zone 2 efforts, usually involve a longer, steadier-state main set.  For example, a common workout is a 10-minute warm up building to Zone 2 followed by a 50-minute steady effort in upper Zone 2.  This would be the structure and intensity level of a typical 60-minute run.

Note that if you are keying off of heart rate when trying to hit certain zones, you should aim to gradually increase your heart rate to the appropriate level during the interval.  You should not blast off at the start in an attempt to raise your heart rate to the target BPM as quickly as possible.  The goal should be to perform the interval at the pace/power at which the target heart rate would stabilize.  The more experience you have tracking heart rate and discovering how your own RPE relates to your various zones, the better you will become at intuitively reaching and maintaining these specific intensities.


When a workout is stipulated as percentage of your threshold heart rate, pace, power, or RPE, you can always convert it to another metric. To do so, refer to one of the linked charts below:

Intensity Metric Conversion Chart Excel

Intensity Metric Conversion Chart PDF