Intensity Guidelines for 80/20 Triathlon

by David Warden and Matt Fitzgerald

Your 80/20 triathlon plan employs a five-zone intensity scale. It is important that you do each workout and interval segment at the right intensity. This guide provides all of the information you’ll need to determine your intensity zones so you can monitor your intensity during workouts appropriately and ensure you’re always in the right zone. There is more than one way to measure intensity. Different metrics work best in different disciplines. Pace is most reliable in swimming, power is the gold standard in cycling, and both pace and heart rate are useful in running. Heart rate works well for cycling also, while perceived effort is an important secondary intensity metric in all three disciplines.

Swim Pace

Pace is the most useful intensity metric for swimming. Your five custom swim pace training zones are based on your swim pace at lactate threshold intensity. The best way to find your lactate threshold pace in the water is with something called the critical velocity test. It’s fairly simple: Go to the pool, warm up with some easy swimming, and then swim 400 meters or yards as fast as you can, recording your time. Rest for several minutes and then swim 200 meters or yards as fast as you can, again recording your time. Your plan has regular swim workouts scheduled every 3-4 weeks to test your critical velocity in order to re-establish your zones. Note that your zones will be specific to meters or yards, and if you train using a different distance you will have to adjust that session (your speed zones for 100 yards will be approximately 10% faster than your speed zones for 100 meters).

After your test, visit the 80/20 Intensity Zone Calculator determine your swim zones, or calculate yourself based on the following formula (the online calculator is much easier):

Critical velocity (CV) = (400 meters/yards – 200 meters/yards) ÷ (400 time – 200 time)

Let’s look at an example. Suppose you swim your 400-yard test in 4:21 (4.35 minutes) and your 200-yard test in 2:02 (2.04 minutes). Your critical velocity, then, is (400y – 200y) ÷ (4.35 min. – 2.02 min.) = 86.6 yards/min. However, it is customary to express critical speed in the form of time per 100 yards. To make this conversion, divide 100 by your critical speed. In this example, 100 ÷ 86.6 = 1.15. So your lactate threshold pace per 100 yards is 1.15 minutes, or 1 minute and 9 seconds. Next, use this number, a calculator, and the table below to calculate your target swim pace range for each of the five training intensity levels. (Note that X and Y represent gaps between zones that are rarely targeted in workouts).

ZONE Pace Range
(as percentage of critical speed/lactate threshold speed)
1 80-85
2 86-90
X 91-95
3 96-100
Y 101-102
4 103-106
5 107+

Run Pace

The 80/20 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.

Cycling Heart Rate

To determine your heart-rate based training zones for cycling, you must first determine your lactate threshold heart rate (LTHR). Your LTHR is your heart rate at the highest cycling intensity you can sustain for one hour. Since this is a rather brutal duration, the protocol to determine LTHR can be modified as follows.

Warm up thoroughly and then begin a 30-minute time trial. That is, increase your cycling intensity to the highest level you feel you can sustain for 30 minutes. Hit the lap button 10 minutes into the 30 minute time trial so you can use your peak average 20 minute heart rate from this 30 minute test (since it takes about 5-10 minutes for your HR to catch up with your intensity). Essentially, you’ll want your peak 20-minute HR from a 30-minute effort. A race is another excellent way to establish your peak 20-minute HR. Your plan has regular cycling tempo workouts every 3-4 weeks to help re-establish your LTHR.

To determine your cycling HR zones, visit the 80/20 Intensity Zone Calculator and enter in your LTHR, which is based on the table below (Note that X and Y represent gaps between zones that are rarely targeted in workouts).

Zone Percent of Lactate
Threshold Heart Rate
1 75-80
2 81-89
X 90-95
3 96-100
Y 101
4 102-105
5 106+

Cycling Power

The most useful way to monitor and control intensity on the bike is by power output (watts). This requires that you have a power meter such as a PowerTap on your bike. If you do not have a power meter, use heart rate and/or perceived effort to monitor and control your intensity on the bike.

To calculate your target power zones, you must first determine your power output at functional threshold power (FTP). This number is approximately equal to your average power output in a one-hour time trial, or about 5 percent less than the your average power output in a 20-minute time trial. Obviously, a 20-minute time trial is more convenient and therefore recommended.

Warm up thoroughly and then cover as much distance as you can in 20 minutes at a steady effort level, preferably on flat or mostly flat terrain. Capture your average power output for this 20-minute effort and then multiply this number by 0.95. The result is your approximate FTP used for calculating zones. A race is another excellent venue to find your FTP, either 0.95 of your normalized power in a Sprint, or 97% of your normalized power in an Olympic-distance event.

To determine your cycling power zones, visit the 80/20 Intensity Zone Calculator and enter in your FTP, which is based on the table below (Note that X and Y represent gaps between zones that are rarely targeted in workouts).

Zone Power Range as Percentage of Functional Threshold Power
1 55-69
2 70-82
X 83-91
3 92-100
Y 101
4 102-110
5 111+

Run Heart Rate

You could perform the same protocol as listed under the Cycling Heart Rate section, but this is a difficult protocol for the run. Instead, the simplest way to determine your run heart rate-based training zones is to back into them through pace. First, follow the instructions under the Run Pace section of this article and use the 80/20 Intensity Zone 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 LTHR using run pace as the foundation. To do this, warm up with 10 minutes of easy jogging and then accelerate to your lactate threshold pave 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 LTHR. 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 X and Y represent gaps between zones that are rarely targeted in workouts).

Also note that your run and bike LTHR are likely to be different, with most triathletes having their run LTHR higher than their bike LTHR.

Zone Percent of Lactate
Threshold Heart Rate
1 75-80
2 81-89
X 90-95
3 96-100
Y 101
4 102-105
5 106+

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 tool 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 Zone 2.

Use the guidelines in the following table to regulate your workout intensity by perceived effort.

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