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Be sure to read Intensity Guidelines for Running. and Understanding Your TrainingPeaks 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 Endurance Lab Run plan


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:

Critical Velocity Intervals Run

5:00 in Zone 1
10:00 in Zone 2
5 x 4:00 @ CV/2:00 in Zone 1
15:00 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.


“5:00 in Zone 1, 10:00 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 10 minutes at Zone 2 intensity.


“5 x (4:00 @ CV/2:00 in Zone 1)” is the interval segment. What these instructions are telling you to do is run for 4 minutes at CV, which, as the pre-activity comments area of this workout explains, stands for Critical Velocity, or the fastest pace you could sustain for 30 minutes, equal to the low-end of Zone 6. You then slow down and jog for 2 minutes in Zone 1, and repeat this sequence a total of five times.


“15:00 in Zone 1” is the cool-down segment.

You’ll execute this by jogging easily for 15 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 preferable 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.


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 4, you can settle into the right effort level even before your device confirms that you’re in the correct zone. Here are some specific tips for mastering each 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 too 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 3

Zone 3 is given a letter name instead of a numerical name because it is generally avoided in training. It’s more of a gap between Zone 2 and 4 than a zone unto itself. Zone 3 represents the “moderate-intensity rut” that most runners get stuck in without realizing it before they adopt the polarized balanced method and learn to slow down in their easy runs and long runs. However, Zone 3 does overlap with race intensity for many runners at the half-marathon and marathon distance. For this reason, many of our Run plans include Steady State Runs, Half-Marathon Pace Runs, and/or Marathon Pace Runs that target Zone X. This zone is also targeted briefly in some Fartlek Runs and Progression Runs.


Zone 4

Zone 4 corresponds to lactate threshold intensity. Thinking in “threshold” terms can help you find this zone and stay in it by feeling. The feeling of running in Zone 4 is often described as “comfortably hard,” or as the fastest speed that still feels relaxed. When you perform a Zone 4 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 this precipice when training in Zone 4.


Zone 5

Like Zone 3, Zone 5 is more of a gap between zones than a one unto itself. It’s a little too fast for threshold workouts, which target Zone 4, and a little too slow for high-intensity interval workouts, which offer more fitness bang for your workout buck when done in Zones 5 and 6.


Zone 6

Mastering this zone is a matter of connecting the pace, power, and/or heart rate numbers that define the zone with what it feels like to run at that pace, power, or heart rate so that you can reliably start each Zone 6 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. Getting it wrong today is the best way to get it right tomorrow.


Zone 7

Zone 7 is almost always used in interval workouts, including Hill Repetitions Runs. This intensity zone ranges from the highest speed you can sustain for a few minutes to a full sprint. So how fast should you run Zone 7 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 7 when these efforts are longer and closer to the top end when the intervals are shorter. For example, if a workout asks you to run a bunch of 1-minute intervals in Zone 7, you’ll want to control your pace so that you can 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 to 2 minutes to “catch up.” As a result, you’ll often not reach the heart rate target during very brief Zone 6 or 7 intervals. Pace and Power are more reliable methods to measure those high intensities. 



Although there are no formally scheduled cross-training sessions in the runs plans, you have a standing option to replace any Recovery Run or Base Run with a nonimpact cardio alternative of equal duration and intensity. You will see periodic reminders of this sprinkled throughout each plan.


So, 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. On the one hand, 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 see a Recovery Run or Base run on your schedule, your running performance will increase more than if you do the opposite. On the other hand, above a certain level, the more you run, the more likely it is that you will develop an impact-related overuse injury such as a runner’s knee. So, if you’re injury-prone or concerned about injury, you may be better off doing some or all of your Recovery Runs and Foundation Runs in a nonimpact cardio exercise modality such as bicycling.


There are two basic approaches to replacing runs with cross-training: the programmatic approach and the as-needed approach. In the programmatic approach, you replace certain runs with cross-training sessions routinely. For example, you might replace your first Base Run of each week with an elliptical workout. In the as-needed approach, you replace runs with cross-training only when soreness or fatigue from prior running makes running again seem inadvisable. Note that these two approaches are not mutually exclusive, and indeed you should cross-train instead of running anytime it seems risky to run, regardless of whether you also practice the programmatic approach. Finding the right balance for you may require some trial and error (See the section The Importance of Listening to Your Body below).


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 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 Run plans, this means all of your cross-training sessions need to be done in Zones 1 and 2.


While it’s important to execute workouts as they were intended to be done, it is not necessary that you execute every one perfectly, and you shouldn’t beat yourself up when a given is not done to the letter. If the 10-km run on your schedule for today ends up being a 9.9-km, 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 training plan. As close is good enough.


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.


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