Understanding Your 8020 Run Plan – 80/20 Endurance

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Understanding Your 8020 Run Plan

by Matt Fitzgerald

Be sure to read Intensity Guidelines for Running and Understanding Your TrainingPeaks.com Structured Workout Plan after reading this article.

A training plan is only as good as its execution. Even the best training plan won’t help you much if you don’t understand it. This article offers guidelines and tips to help you get the most out of the 80/20 Run plans.

Anatomy of a Workout

Each workout has three basic elements. The first two are duration/distance (how long the workout is) and intensity (how fast the workout is). The third is structure, which is how the workout is divided into segments of various lengths and intensities. The workout descriptions you see in the training schedules provide information about duration/distance, intensity, and structure in a condensed format.

Let’s look at one example:

Long Interval Run

5 minutes in Zone 1, 5 minutes in Zone 2, 5 x (3 minutes in in Zone 4/2 minutes in Zone 1), 5 minutes in Zone 1

We chose this example because it has a fairly complex structure. Nevertheless, it’s not at all difficult to decode and follow. The workout has three segments: a warm-up, an interval set, and a cool-down.

“5 minutes in Zone 1, 5 minutes in Zone 2,” is the warm-up segment. You’ll execute this part by jogging easily for 5 minutes at Zone 1 intensity and then running for 5 minutes at Zone 2 intensity.

“5 x (3 minutes in in Zone 4/2 minutes in Zone 1)” is the interval segment. What these instructions are telling you to do is run for 3 minutes in Zone 4, then slow down and jog for 2 minutes in Zone 1, and repeat this sequence a total of five times.

“5 minutes in Zone 1” is the cool-down segment. You’ll execute this by jogging easily for 5 minutes at Zone 1 intensity. There is an almost infinite variety of workout structures, but if you understand how to interpret and apply the example we just covered, you can do the same with any other workout.

Note that you have the flexibility to perform the workout at any point within the zone. For example, if the workout segment calls for Zone 1, and your Zone 1 heart rate is 115 to 129 bpm, you can perform the segment anywhere within that range. Continually performing workout segments at the upper end of a zone does not always lead to superior results. Sometimes appropriate recovery requires performing Zone 1 and 2 segments at the low end of the range. It is also best to perform moderate and high intervals consistently rather than intensely. Performing a set of 5 intervals at mid-Zone 3 is preferred to performing each of 5 intervals at a different point in Zone 3. Only when you are well-recovered and can perform intervals consistently is it recommended to execute the segment at the high end of the zone.

Getting to Know Your Zones

Perhaps the trickiest part of executing the workouts that are prescribed in a training plan is running at the right intensity in each segment. You will find complete guidelines for using our seven-zone intensity scale in our Intensity Guidelines. But simply reading these guidelines alone won’t enable you to fully master the skill of running in the right zones. A certain amount of experience is also required.

Don’t worry: It doesn’t take long to develop a feel for the various zones, so that, for example, when you start a 3-minute interval in Zone 3, you are able to settle into the right effort level even before your heart rate monitor or GPS watch confirms that you’re in the correct zone. Here are some specific tips for mastering each individual zone:

Zone 1

Zone 1 is a very low intensity. Staying within it usually requires that you actively hold yourself back to a pace that’s slower than your natural running pace. The common exception is when a Zone 1 recovery jog follows a tiring high-intensity effort. The important thing to understand is that it’s almost impossible to go too slow when you’re aiming for Zone 1, whereas it’s very easy and all to common to go too fast.

Zone 2

Zone 2 is fairly broad. You might wonder, “Where exactly within this zone should I be?” As a general rule, we encourage runners to go by feel. If you feel strong, run near the top end of Zone 2. If you feel tired or sluggish, go ahead and allow yourself to run near the bottom end.

Zone X

Zone X is the trap that most runners fall into, and avoiding it is one of the key objectives of the 80/20 Training approach. Just easy enough to not be uncomfortable, yet just hard enough to make you think you’re getting a good workout, this lukewarm intensity offers minimal value in increasing fitness while generating fatigue that interferes with recovery and with performance in subsequent intense workouts. Avoiding Zone X allows you to go harder on the hard days and gain more fitness.

An Exception for Zone X

For half and full marathon athletes, Zone X can actually be an appropriate racing zone. If you are willing to take the risk on race day, you'll want to incorporate some Zone X into your training.

To do so, some workouts in your run plan will give you "permission" to include Zone X in the workout. How much? Again, it depends on how much risk you're willing to take. Additional Zone X in training will compromise your ability to recover, and if using it on race day it will increase the possibility that you'll crash and burn.

In general, if you are willing to take the risk, replace your Zone 2 work with Zone X using the guidelines below, and only for workouts that specify the Zone X option.

Week 1-5: replace up to 20% of Zone 2

Week 6-9: replace up to 30%

Week 10+: replace up to 50%

Zone 3

Zone 3 corresponds to lactate threshold intensity and marks the beginning of “legitimate” moderate to high intensity. Thinking in “threshold” terms can help you find this zone and stay in it by feel. The feeling of swimming, riding, or running in Zone 3 is often described as “comfortably hard,” or as the fastest speed that still feels relaxed. When you perform a Zone 3 effort, imagine there’s a cliff edge in front of you that represents the feeling of strain that accompanies faster speeds. Always stay one or two steps back from that precipice when training in Zone 3.

Zone Y

While Zone Y is not as detrimental as Zone X, this narrow intensity gap simply isn’t targeted by any of the tried-and-true workout formats. It’s a little too fast for threshold workouts, which traditionally target Zone 3, and a little too slow for high-intensity interval workouts, which offer more fitness bang for your workout buck when done in Zones 4 and 5.

Zone 4

Zone 4 is the narrowest Zone. Mastering this zone is a matter of connecting the pace and/or heart rate numbers that define the zone with what it feels like to run at that pace or heart rate, so that you are able to reliably start each Zone 4 effort at the right intensity. If you mess it up the first few times, either going too slow or too fast, don’t sweat it. in fact, getting it wrong today is the best way to get it right tomorrow.

Zone 5

Zone 5 is almost always used in interval workouts similar to the one given as an example earlier in this article. This intensity zone ranges from the highest speed you can sustain for a few minutes all the way to a full sprint. So how fast should you actually run Zone 5 efforts? Tailor your pace to the specific format of the workout. The rule of thumb here is to run closer to the bottom end of Zone 5 when these efforts are longer and to run closer to the top end when the intervals are shorter. For example, if a workout asks you to run a bunch of 90-second intervals in Zone 5, you’ll want to control your pace so that you are able to run all of the intervals at the same speed without slowing down. But if a workout prescribes a set of 20-second intervals, you’ll want to run them as relaxed sprints.

When using heart rate to measure intensity, you’ll soon discover that your BMP takes 1-2 minutes to “catch up.” As a result, you’ll often not reach the heart rate target during very brief Zone 4 or 5 intervals. Pace and Power are more reliable methods to measure those high intensities. This issue can also be resolved by using the 80/20 Run and Bike Zones Garmin App, where you can have both real-time HR and your custom 80/20 Pace or Power zones displayed on your device at the same time.

You may wonder why a seven-zone intensity scale such as ours tops out at Zone 5. The reason is that in the original version of the scale, Zone X and Zone Y were not explicitly named. Instead these zones existed only as gaps between Zones 2 and 3 and between Zones 3 and 4, respectively. The first gap was created to ensure that low-intensity exercise efforts did not accidentally bleed into moderate intensity and the second to encourage athletes to commit to either moderate or high intensity. Nevertheless, many athletes found the gaps confusing, so we modified the 80/20 intensity scale in a manner that eliminates gaps and the confusion they cause while preserving the distinction between untargeted zones (X and Y) and targeted zones (1-5).


In the advanced 80/20 run plans, some days have two workouts scheduled in the same day. These are always scheduled with the first workout as a Run and the second as a Run or Cross-train. Regardless of whether you choose to run or cross-train the second workout, the two workouts would ideally be done in the AM and PM, or at least as far apart as possible. In extreme circumstances, the two workouts can be combined together, but preferably the second workout is simply moved to another day of the week.


When should you cross-train and when should you run? There are two competing, but equally valid, truths to consider when deciding whether to run or to cross-train. First, the more you run, the more you’ll improve as a runner. The principle of specificity teaches us that if you run instead of cross-training each time you’re given the option, your running performance will increase more than if you do the opposite. Second, the more you run, the more likely it is that you will develop an impact-related overuse injury such as runner’s knee. So, if you’re injury prone or concerned about injury, you may be better off doing some or all of these option workouts in a nonimpact cardio exercise modality such as bicycling Finding the right balance for you may require some trial and error (See the section The Importance of Listening to Your Body below). When in doubt, play it safe and cross-train, and even if you’ve been durable in the past, don’t do all of the option workouts as runs if this would entail running a lot more frequently than you have in the past.

The best cross-training activities are those that are most similar to running without the impact element. Pool running, antigravity treadmill running, indoor and outdoor cycling, elliptical running, outdoor elliptical biking, steep uphill treadmill walking, indoor and outdoor cross-country skiing, inline skating, and steep uphill treadmill walking have all been used successfully. Strength training is a completely different sort of cross-training that we strongly recommend but as a complement to aerobic cross-training rather than a substitute for it. See Incorporating Strength Training to Your Plan for ideas on how to incorporate strength training into your plan.

Note that effective 80/20 training requires that you spend 80 percent of your combined aerobic training, encompassing running and cross-training, at low intensity. In the case of our 80/20 Run plans, this means all of your cross-training sessions need to be done in Zones 1 and 2.

In addition to performing cross-training on the days the plan offers cross-training, you may replace scheduled runs with cross-training sessions whenever pain or soreness makes running inadvisable. When you do, simply match the duration, intensity, and structure of the run in your chosen cross-training activity. For example, if the run workout prescribes 3 x (3 minutes Zone 3 / 3 minutes rest), this can be done via heart rate zones or perceived effort on a bike, or in any other legs-dominant nonimpact aerobic modality.

Perfection is Overrated

While it’s important to execute workouts as they were intended to be done, it is not necessary that you execute every perfectly, and you shouldn’t beat  yourself up when a given is not done to the letter. If the 10-mile run on your schedule for today ends up being a 9.9-mile, no big deal.

There’s a well-known story about a legendary running coach who always had his athletes run 187-meter hill repetitions. Another coach who admired this legendary coach emailed him to inquire about this very precise distance. “Why 187 meters?” he asked, assuming there must be some deep physiological rationale for it. But the legendary coach came back with this answer, “Why 187 meters? Because that’s how long the hill closest to our training camp is.”

Keep this story in mind as you can execute your 80/20 Run plans. As with horseshoes and hand grenades, close is good enough.

The Importance of Listening to Your Body

There are some times when executing the workouts in your training plan to the very letter is a bad idea. For example, if you get three intervals into a nine-interval workout and you feel absolutely terrible, you should probably stop, or replace the remaining intervals with an easy jog. (A helpful guideline to follow is this: If your pace for a given interval is more than 3% slower than it was in the previous interval, terminate the interval set and complete the remaining time in Zone 1 or 2.) Similarly,  if you wake up one morning with a really sore foot that hurts even to walk on, you should not run that day.

A training plan is really an attempt to predict the future. The many workouts that comprise a training  plan represent what you should do if everything goes perfectly-that is, if there are no days when you feel really lousy or have an alarming sore spot. But things seldom go perfectly  all the way through a training program. It’s important that you listen to your body at every step of the process and make adjustments as necessary based on what your body is telling you.

Glossary of Workout Codes

AcronymLong NameDescription
RAeRunning Aerobic IntervalsThis running aerobic interval set is intended to prepare the athlete for the specific intensity and stress of half and full Ironman racing. The Zone 2 intervals should be done at the expected intensity of the athlete’s next half or full Ironman. For new athletes, this will be low to mid Zone 2. For more experienced athletes, this intensity will take place in upper Zone 2. For advanced athletes, these intervals can even include Zone X, a rare exception to the 80/20 system.
RAnRunning AnaerobicWhen executed properly, this anaerobic interval set is the most effective method at increasing an athlete’s VO2max. While VO2max is only one component an athlete’s success, it is a direct predictor of endurance performance. Additionally, VO2 intervals have been proven to be more effective at improving overall economy than submaximal (threshold) or supramaximal intervals. Thus, a successful integration of these intervals in the General phase of training places the athlete in an advantageous position for the upcoming Specific phase, and ultimately their endurance performance results. These intervals are challenging, and the athlete must take great care to not perform them at a Zone 3 or Zone 5 intensity. The unusually high rest period compared to a Zone 3 work reflects the difficulty of the interval. The 80/20 principle is fundamental to executing these anaerobic intervals, as the athlete has deliberately trained easy 80% of the time in order to have the form necessary to maintain this repeated Zone 4 intensity. These anaerobic intervals are permission to go very hard. Be bold, but measured. A successful anaerobic interval set will have the athlete’s output (pace, speed, power) be almost identical for each interval, in Zone 4, and without fade.
RCIRunning Cruise IntervalsMuscular endurance is arguably the most important ability an endurance athlete can develop, and no other interval improves muscular endurance better than the cruise interval. The application of the cruise interval is broad. The only interval type appropriate for both the General and Specific phase of training, its benefit spans all triathlon distances. The 80/20 principle makes the cruise interval possible, by ensuring the athlete is sufficiently rested in order to achieve the required Zone 3 intensity. The cruise interval is the antithesis of Zone X. A successful cruise interval set has the output for each interval nearly identical to the previous, while maintaining solid Zone 3 intensity. Consider reducing the rest time from 3 minutes to 2 minutes and then 2 minutes to 1 minute if previous cruise intervals sets have been successful.
RestRestAthletes can consider adding a strength workout to this day, and beginner swimmers can consider adding a swim. However, rest is a critical element of improving fitness. Adding activity to this rest day is a high risk decision. Very few athletes, of any ability level, can maintain a 16+ week training program without regular days off.
RFRunning FoundationDiscipline is required for the running foundation set. If rested, the temptation is to drift into Zone X. However, save your energy for the 20% of the 80/20 plan, and stay in Zone 1-2 for this workout. Avoid running with individuals who will tempt you to exceed Zone 2.
RFFRunning Fast FinishOne of the few workouts designed with the intensity scheduled for the end of the workout, the intent is to expose the athlete to high intensity while slightly fatigued. An excellent simulation of a triathlon finish.
RHRRunning Hill RepeatsBecause the run hill repeats are so short, the athlete will have to often use perceived effort to gauge intensity, as HR may not reach Zone 5 prior to the interval ending. This workout is an excellent time to go very hard, but aim to have each interval with a similar output and avoid fading near the end of the interval. If hills are unavailable, a treadmill is recommended. If neither option is available, the prescribed intensity and duration can still be met.
RLRunning LongSimilar to the frequent Run Foundation workout, the Long Run is measured by distance to ensure the athlete experiences the required stress. Upper Zone 2 is recommended. Half and full marathon athletes may benefit from a rare Zone X exception and spend a majority of their time in Zone X for this workout. Every effort should be made to “negative split” the workout, where the second half of the run is slightly faster than the first half. Complete this workout by distance only, any planned time associated with this workout is a broad estimate.
RLFFRunning Long with Fast FinishThis workout is designed to teach the athlete’s body and brain to resist and manage fatigue, placing the most stress at the very end of the workout. Half and full marathon athletes may benefit from a rare Zone X exception and replace some of the Zone 2 time with Zone X. Complete this workout by distance only, any planned time associated with this workout is a broad estimate.
RLIRunning Long IntervalsHighly intense and rarely used, these heavy Zone 4 intervals mimic their fraternal twin, the anaerobic intervals (code RAn). The extended Zone 4 duration and reduced recovery interval reserve this workout for advanced athletes.
RLMSRunning Marathon Simulator The Marathon Simulator is intended to introduce the athlete to the specific stress, pacing nutrition, clothing and terrain of race day. Pre-workout meal and preparation should simulate the environment of race day as much as possible. The course for this workout should be similar in nature to the marathon race course. Pacing should measured to negative split the 16 miles. Complete this workout by distance only, any planned time associated with this workout is a broad estimate.
RLSPRunning Long with Speed PlayA successful execution of this workout would have the pace of the Zone 3 intervals remain steady or slightly increase throughout the activity. You may be cursing Matt and David by the end of the intervals, but you’ll be praising them on race day. Complete this workout by distance only, any planned time associated with this workout is a broad estimate.
RMIRunning Mixed IntervalsComplex in execution, the reward is high. This workout is best done pre-programmed into a watch (such as a Garmin).
RRRunning RecoveryTake advantage of this day with active recovery. Avoid even Zone 2.
RSIRunning Short IntervalsUnlike the very similar running hill repeats (RHR) the running short interval is done on a flat surface. Feel free to go hard.
RSPRunning Speed Play Not to be confused with the Zone 5 running short interval (RSI), running speed play is done in Zone 4 with much shorter recoveries. If done in Zone 5, the athlete will fade.
RTRunning TempoThe running tempo workout does an excellent job at muscular endurance, and should be used as a method to either verify or re-establish current HR Zones. A difficult workout, pacing is key. Start slightly lower and finish stronger. Some brief forays into Zone 4 are acceptable.
RTaRunning TaperBrief, but fast intervals to promote the taper.