Training Science Series #9 - A Brief Introduction to Zone Training

The sports lab is the best place to determine accurately the AT and LT thresholds. However, you can use the next best thing — testing them with specific workouts. I get my athletes to run different workout tests to determine their aerobic and anaerobic threshold zones.

Training Science Series #9 - A Brief Introduction to Zone Training

The sports lab is the best place to determine accurately the AT and LT thresholds. However, you can use the next best thing — testing them with specific workouts. I get my athletes to run different workout tests to determine their aerobic and anaerobic threshold zones.

This is an article series designed to help further educate my Performance Coaching clients, but also anyone interested in learning how to train more successfully. If you are interested in getting fitter -- irrespective of whether you are a novice or regular athlete -- then please read through this series and learn more about the endurance training process. I also hope to welcome you onboard as your performance coach one day if you need mentoring to reach the summit of your athletic potential!

Understand the Process to Commit 100% to the Process


The sports lab is the best place to determine accurately the AT and LT zones. However, you can use the next best thing—testing them with specific workouts using Heart Rate. At Couch to the Summit Performance Coaching, I get my athletes to run different workout tests to determine their aerobic and anaerobic threshold zones. We regularly retest these heart-rate thresholds, to ensure our training zones are optimised as fitness changes occur. Once we have the heart-rates, we can use maths to calculate the heart-rate zones to be used in training. I use five heart-rate zones (with an added zone for recovery) to help my athletes understand the training intensities they should be applying for their daily workouts. Zone’s 1 and 2 (beneath the AT) are used for aerobic capacity training, while zones 3-4 (above the AT) are used for utilization training. Zone 4 is essentially open-ended up on the upper range to the max HR. Zone 5 (sprint pace) can be lightly used either during capacity or utilization training periods largely for muscular strength training more than anything.

An example below of the zones for an athlete with an AT of 153 and LT of 170bpm:


Figure 9 - Heart Rate Zone Ranges for an Athlete with AT at 153bpm and LT at 170bpm.

Low Intensity Zones for Capacity Training


Very easy effort, >20% lower than the AT heart-rate. This is a relatively easy effort and plays a minor role in improving aerobic fitness, but aids recovery by delivering more blood flow into the muscles. An activity recovery session is always preferred to doing nothing for optimal recovery from hard training. You should always feel better right after or within a few hours of a recovery training session, and definitely should not feel more fatigued from this session.

Zone 1: Recovery and Basic Aerobic Conditioning

Zone 1 is the heart rate range in the zone 10-20% lower than the AT heart-rate. This training zone helps to develop fat metabolism for fuelling, build mitochondrial mass, increase capillary density and other beneficial aerobic adaptations throughout the slow-twitch muscle fibers. It’s heavy application in capacity training prepares the body for greater fatigue resistance and handling the impact loads of future training, helping to offset both fatigue and injury. This zone should be easy enough that you may sometimes feel “guilty” when you are done, because so much was left in the tank. You should be able to keep this pace for several hours or more and easily hold a conversation with someone.

Zone 2: Aerobic Capacity and Endurance: 

Zone 2 is the heart rate range in the zone 1-10% lower than the AT heart-rate. Zone 2 is crucial to endurance performance, and has the greatest impact on raising the AT. The same benefits seen in Zone 1, apply to Zone 2 training, but the added demands encourage greater adaptations. Zone 2 has the purpose of improving lactate clearance capacity by increasing the number of mitochondria to clear lactate mainly in slow twitch muscle fibers as well.1 Zone 2 should feel relatively easy, at least in the beginning, but you should feel as though you have to work if you've been doing this for more than an hour. The speed should feel like a reasonably hard effort where you start breathing heavily. Zone 2 workouts create too much residual fatigue for aerobically efficient athletes, but are a staple in the diet of aerobically deficient ones. The AT heart-rate sits at the top of Zone 2 and the bottom of Zone 3, and this heart-rate is useful for pacing in ultra-endurance race efforts.

High Intensity Zones for Utilization Training

These zones have high energy demands and shift from fat to sugar metabolism. These are used sparingly but have tremendous benefits for increasing fitness rapidly.

Zone 3: Between Aerobic Threshold and Lactate Threshold:

Zone 3 between the two thresholds, is the "Race Pace" zone and is a mixed fat and sugar fuel source zone. This zone has an immensely powerful training effect, and is why novices end up doing so much utilization training in this zone to make training time more efficient. The regular overuse of this training zone leads to diminishing returns and performance decline, so it should not be used more than 10% in the overall yearly training load (including the race efforts in that 10%). Aerobically deficient athletes should focus more on Zone 2 training, because they will get the most benefit there than doing Zone 3 training.

When aerobically efficient athletes use small amounts of Zone 3 training, this can help elevate and peak their performance ready for race efforts. Somewhere in Zone 3 is typically the goal race pace heartrate for races (other than really long ultramarathons) as it sits just beneath the lactate threshold. This will allow you to sustain maximum pace and intensity for long periods of time without lactate accumulation.

You know when you are in Zone 3 as your breathing is laboured and you may not be able to sustain the effort for longer than a couple of hours or less.  Elite athletes will be able to hold this pace for longer.

Zone 4: Aerobic Vo2Max and Anaerobic Capacities

Zone 4 the pace slightly above the LT when you are going all out on a short interval ranging from 5 to ~10 minutes. The duration you can sustain depends a lot on your overall athletic capacity. You know you are in this zone as your legs will be aching and your heart pounding. This zone also has a powerful training effect, as any time spent training about the LT forces greater development of both aerobic and anaerobic metabolic systems. Both high intensity and endurance training increases the body’s ability to transport lactate away from fast twitch fibers.2

These adaptations occur fast, so when used once a week during utilization training cycles, you should notice fitness increases each week. The downside is you need more recovery following these workouts due to the imposed stress they cause on the body.

Most zone 4 training is done in short interval format with a 2:1, 3:1 or (sometimes) a 4:1 work to rest ratio. Therefore, a 6-minute interval should have about 2-3 minutes recovery between each effort. Typically, the shorter recovery time, the better, to encourage greater LT development. Most novice athletes will not be able to sustain intensities above the LT for more than a few minutes. Elite athletes can hold the pace for longer. Typically zone 4 intervals are a max effort intensity tailored to the specific interval length. Therefore, a zone 4 interval of 2 minutes will be at a pace the athlete can only sustain for two minutes, while a Zone 4 interval of 10 minutes, will be at a pace slightly slower, but still maxes out after 10 minutes.

Zone 5: Anaerobic Power / Muscular Strength Endurance 

This is your max effort sprint interval pace, a pace you could only sustain for between 5 and 120 seconds. This is a completely anaerobic effort using fast-twitch muscle fibers and muscle glycogen for fuel, featuring rapid lactate accumulation.  There are greater injury risks with small application of Zone 5 training, but it can be used through a capacity training cycle due to its important muscular strength developing aspects.

Zone 5 training should always be done in interval format with long rest periods between each interval to allow the ATP stores in the muscles to replenish prior to the next interval.

There are multiple ways for you as an athlete to determine what is the appropriate pace for the zone:

  • 1. By Rate of Perceived Exertion (Intuition) – Most Recommended
  • 2. By Nasal-Breathing – Also Highly Recommended
  • 3. By Heart-Rate – Use for Running Tests and Sparingly in Training to confirm RPE

I encourage all my athletes to eventually train by intuition (or feel) using RPE and develop nose-breathing pacing as your go-to approach specifically for keeping yourself within the green zones (if you’re unsure). The way you I would prefer you to discover the right intensity for the low intensity zones is through nose-breathing at first. This can be combined with RPE and a heart-rate monitor to give an accurate assessment of your training zones. We do use heart-rate pacing but there are limitations to reliance on tools for pacing (temperature, sweat levels, recovery levels, caffeine intake etc...) – intuition and feeling is always the best way since it is most applicable to how you are feeling on each specific day. You can use tools to help you develop better intuitive insight, but you should never rely solely on one artificial tool to pace yourself on every run. For example, what do you do when the tool failures or gives inaccurate readings? Think of these tools are training wheels. RPE is the best way to pace for mountain focused endurance training. Also its much safer to be running without looking down at your watch regularly.

Rate of Perceived Exertion (RPE)

Rate of Perceived Exertion (RPE) is nothing more than a scale out of 1-10 of how hard you feel you are breathing. This is the system I would prefer you are using to pace your training within the selected zones we establish for training workouts.

Using this scale, your forever pace (the pace you could run all day) should be around 5-6 out of 10. A challenging aerobic pace would be 7, long intensity intervals would be 8, short-intensity intervals 9 and sprints 10. Sedentary activities would be in the 1 to 3 range.

Zone R Recovery would be around 4 out of 10. You should only be breathing a bit faster or deeper than when you walk at a brisk pace. You should use nasal breathing and it should feel easy to breathe through the nose.

Zone 1 Conditioning (Endurance) would be 5-6 out of 10, breathing should be deep and rhythmic but not laboured, and you should be able to have a normal conversation if you were with a friend without any breathing difficulty while talking and exercising at the same time. It should feel relaxing and a pace that you could feel like you can run for hours on end (aerobically … you may not be able to mechanically run for hours on end, yet). You should use nasal breathing and it should feel comfortable to breathe through the nose.

Zone 2 Foundation (Steady State) would be 7 out of 10 breathing begins to feel laboured. You can hold the pace for multiple hours (aerobically … you may not be able to mechanically run for hours on end, yet), but not all day. You can confirm the pace by speaking a few sentences and if you can do it without gasping for air then you are likely under the aerobic threshold. You should use nasal breathing and it should feel moderately difficult to breathe through the nose.

Zone 3 Threshold (Tempo) would be 8-9 out of 10. You can hold the pace for up to 1 hour, so similar to the pace you would use in a 5-10km race. You can only speak a few words at a time. The easiest way to know if you temporarily go above Zone 3, is if your breathing goes from very deep and laboured to short and rapid. If you’re a relatively untrained athlete you can still nasal breathe and be in Zone 3, so if you are not a well-trained athlete you should also use RPE more than nasal breathing to determine whether you are Zone 2 or Zone 3. However, well trained athletes will not be able to nasal breathe in Zone 3.

Zone 4 Speed Intervals (VMA) would be 9-10 out of 10. Breathing is intense, short and rapid. You can’t maintain the pace for more than 5 minutes. You could only speak a single word or none.

Zone 5 Sprints would be 10 out of 10. Zone 5 is a sprint, that you can only hold for 10 seconds. It should feel 10 out of 10. You can’t speak. The only way training by feel works well is if you are totally honest with yourself and you have discipline to keep those Zone 1 and 2 runs in the green zone. It’s very common for your pace at Zone 1 to slowly creep up as your run goes on since you naturally tend to feel better after a warm-up and it can be easy to start going faster without realising it.


Rule 1: It’s better to be too slow than too fast when working in the green zones. Think easy on the easy days.

When working in the yellow, orange and red zones above aerobic threshold, a bigger challenge is athlete’s often not pushing themselves hard enough and not coming into those sessions rested enough because their green activities are too fast and not restful enough to their physiology. You want to avoid being a once-paced athlete where you are neither slow nor fast. This is called the “black hole of training”. Make sure your training intensities are highly polarised: easy on the easy days, hard on the hard days. You don’t need to be pushing at 100% all the time here, but you should at least be feeling you are going above 80% intensity on these days.

Rule 2: It’s better not to be too slow in the yellow, orange and red zones. Think hard on the hard days.

It is my job to monitor whether you are training improperly, and I will set you back on the path if I see you falling out of the prescribed zones too frequently. Remember this is an art, not a science, so you don’t have to sit right in the zone every single second of the workout – the training zone means MOST OF THE TIME, instead you should objectively feel that after the workout is concluded whether it was easy, moderate or hard. If you hit a short hill in Zone 1 workout and your intensity level goes up into the yellow or orange zones, that is perfectly fine, what we aren’t looking for is doing it for the entire duration of runs over a long period of time.

The goal is not perfection, just an averaging out of the intensity of the run. Pacing should never stress out an athlete otherwise it can impact the training response. I've seen many athletes obsess about their heart rate zones to the detriment of their training outcomes, and also often they're stressing out over bad readings from their HR devices. Therefore, RPE is always the first place to check in with how you are feeling, and we can look at HR in post-run analysis to get a better handle on the workout outcomes (and also determine if the readings are valid or bad data).

Next Article -> Part Ten - How to Choose Which Zones to Train in Regularly

Related Posts

Training Science Series #8 - Introduction to Threshold Training

A strong fat-adapted aerobic base is crucial to longevity in any endurance sport, and is done by performing a large volume of work beneath what is called the Aerobic Threshold. Athletes with a high aerobic capacity can maintain high speeds over long distances at a low metabolic cost.

Training Science Series #10 - How to Choose Which Zones to Train in Regularly?

This is completely dependent on the conditioning of the athlete and whether the athlete is considered aerobically deficient or not. This is also the secret sauce of coaching and is completely dependent on the athlete, their level of fitness, their short-term and long-term goals, and how they are responding to training.