What are endurance training zones?

In order to get the most benefit from the time you invest in training, you need to train at a variety of different intensities, from the lowest intensity that qualifies as exercise all the way up to maximum effort. The reason is that each intensity contributes to endurance fitness in different ways.

Intensity is relative, of course. A cycling speed or running pace that represents low intensity for an elite athlete might be high intensity for a beginner. Therefore it’s important to determine what the various intensity levels are for you and keep them current as your fitness level changes. The best way to do this is to use lactate threshold testing to establish your personal training zones. Note that, because each endurance discipline uses different muscles in different ways, and because intensity can be measured in different ways across disciplines (e.g., bike power vs. running pace), you will need to conduct separate lactate threshold tests and establish separate zone sets for each discipline you train in.

BSXinsight employs a five-zone system that is summarized in the table below. The purpose of this article is to explain the purpose and benefits of each zone and offer guidelines for training in them. It is intended to supplement the Quick Start guide that came with your device.

 

BSXinsight Training Zones

  Running   Cycling  
Zone Heart Rate Pace Heart Rate Power
1. Recovery <80% <81% <80% <69%
2. Aerobic 81-89% 82-92% 81-89% 70-83%
3. Threshold 94-100% 94-100% 94-100% 92-100%
4. VO 2 max 102-106% 104-108% 102-106% 102-110%
5. Speed 107% + 109% + 107% + 111% +

All numbers expressed as percentage of lactate threshold heart rate, pace, or power.

 

Zone 1: Recovery

Zone 1 is the lowest intensity of exercise that is sufficient to improve cardiovascular fitness. The advantage of Zone 1 is that it is very gentle, subjecting the body to little stress. But for this same reason, it takes a lot of Zone 1 training to get significant benefits. Generally, athletes are better off spending their time in Zone 2, which offers greater benefits with only slightly more stress.

The best use of Zone 1 is in recovery workouts. These are slow-and-steady sessions of short to moderate duration performed as the next workout after a challenging workout of high intensity or long duration. It is widely believed that recovery workouts actually accelerate the recovery process, but this isn’t true. Recovery workouts simply don’t interfere with the recovery process while also supplying a gentle aerobic conditioning stimulus. Therefore, an athlete who consistently does recovery workouts instead of taking the day off after his or her more challenging workouts will become fitter without any greater risk of burnout.

Zone 1 is also for appropriate for warm-ups, cool-downs, and active recovery periods between high-intensity intervals. Except when they are done in a state of high fatigue (as they often are), Zone 1 efforts feel very comfortable. It is possible to carry on a normal conversation at this intensity, which is lower than the intensity that most athletes naturally adopt during “easy” workouts, so expect to have to hold yourself back whenever it is targeted.

 

Example Workout

30 minutes steady in Zone 1

 

Zone 2: Aerobic

Zone 2 represents the high end of the low intensity range. Training in Zone 2 strengthens the cardiorespiratory system and improves the fat-burning capacity of the muscles. When Zone 2 efforts are done in large volumes and/or sustained for prolonged periods, additional benefits accrue, including improved movement economy, greater fatigue resistance, and increased durability.

Most athletes have a very large capacity to adapt to Zone 2 training. In other words, the more of it you do, the fitter you get, provided you don’t build up too quickly. For this reason, the majority of your total training time should be spent in this Zone, which is most often targeted in “easy” or “foundation” workouts consisting of a steady Zone 2 effort sandwiched between a warm-up and a cool-down in Zone 1, and long workouts, which are simply extended easy/foundation workouts.

Research has shown that most athletes naturally adopt an intensity that is slightly above Zone 2 in the above-described workouts. This is a costly mistake, because efforts just above Zone 2 are significantly more stressful to the nervous system than efforts slightly below it. Consequently, athletes who consistently train above Zone 2 when they should be in Zone 2 tend to develop a chronic burden of fatigue that they might not even notice but that nevertheless sabotages their fitness development. Thus, as with Zone 1, you may need to hold yourself back, going a little slower than your body wants to, in workouts that target Zone 2.

 

Example Workout

5 minutes in Zone 1

30 minutes steady in Zone 2

5 minutes in Zone 1

 

Zone 3: Threshold

Zone 3 is a moderate intensity. Physiologically, it falls between the ventilatory threshold, which is the exercise intensity at which the breathing rate spikes, and the lactate threshold, which is the intensity at which lactate, an intermediate product of aerobic metabolism, begins to accumulate in the blood. Well-trained athletes are able to sustain an effort at lactate threshold intensity for about 60 minutes, beginners not quite as long.

Training in Zone 3 is a powerful fitness booster. Athletes who add it to their training see significant improvements in how long they are able to sustain moderately fast speeds and how fast they can go for long durations. Zone 3 is typically incorporated into endurance training in the form of tempo or threshold workouts, which consist of an extended Zone 3 effort that falls in the middle of a workout that is otherwise done in Zones 1 and 2. Other ways to hit Zone 3 include fast-finish workouts, in which a low-intensity workout ends with a Zone 3 surge, and cruise intervals, which consist of two or more blocks of Zone 3 work separated by low-intensity active recoveries.

Being in Zone 3 is often described as “comfortably hard.” At this intensity, you are still fully in control of your breathing and can utter short sentences without falling behind in your breathing, but if you went any faster this would no longer be the case.

 

Example Workout

5 minutes in Zone 1

5 minutes in Zone 2

20 minutes in Zone 3

5 minutes in Zone 2

5 minutes in Zone 1

 

Zone 4: VO 2 max

Zone 4 is a narrow zone that tops out at VO2max, which is the exercise intensity at which an athlete’s body is consuming oxygen at the highest rate it is capable of. The typical trained athlete can sustain a VO2max effort for several minutes. Efforts at the low end of Zone 4 can be sustained somewhat longer. Training in Zone 4 increases aerobic capacity, or the body’s ability to use oxygen to produce energy, and improves fatigue resistance at high exercise intensities.

Zone 4 is almost always targeted in interval workouts, where multiple short efforts in Zone 4 are separated by brief active recoveries at low intensity. This format enables athletes to accumulate more total time in Zone 4 than they could if they did just one exhaustive effort at this intensity.

 

Example Workout

5 minutes in Zone 1

5 minutes in Zone 2

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

5 minutes in Zone 2

5 minutes in Zone 1

 

Zone 5: Speed

Zone 5 ranges from just above VO2max all the way to a full sprint. Training in this zone increases anaerobic capacity (or the ability to generate muscle energy without oxygen) and movement economy. As the highest exercise intensity, Zone 5 is quite stressful to the body. A little Zone 5 training goes a long way, and more than a little is counterproductive.

Like Zone 4, Zone 5 is almost always targeted in interval workouts. One variation is hill repetitions, where Zone 5 intervals are done on an upward slope to add a strength-building dimension to the workout.

 

Example Workout

5 minutes in Zone 1

5 minutes in Zone 2

10 x (1 minute in Zone 5/2 minutes in Zone 1)

5 minutes in Zone 2

5 minutes in Zone 1

 

It’s All About Balance

The most effective training programs not only include all five intensities but balance them optimally. Research has demonstrated that athletes improve the most when they do approximately 80 percent of their training in Zones 1 and 2 and the remaining 20 percent in Zones 3-5. The BSXinsight/Matt Fitzgerald training plans available online for cyclists, runners, and triathletes are based on this 80/20 principle.

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