Whether you’re an experienced triathlete or just starting to dig deeper into the world of structured endurance training. You’ll most likely have come across various references to training zones. From workout descriptions on indoor training platforms like Zwift and ROUVY. To folks singing the praises of Zone 2 training as the holy grail for endurance athletes. But what do these training zones actually mean?
Training zones aren’t just a buzz phrase. Knowing what each zone means, and the fitness adaptations they can stimulate, can help you to get really specific with your workouts so you can get the most out of your training hours. We take a look at what training zones are, the benefits of working in different training zones – and how to make sure you’re actually training in the zone you intend to be.
What are training zones?
Training zones are quantified levels of exertion/effort for physical activity. They can be expressed using heart rate, power output (for cycling), pace and perceived exertion ranges. Each training zone will stimulate a slightly different energy system in the body, and therefore bring about different training adaptations. Athletes competing in sports that require short, sharp bursts of energy such as sprinting are likely to focus more on training in the upper zones. Meanwhile athletes who take part in events lasting over an hour, i.e. triathletes, are likely to perform the bulk of their training in the lower zones to build endurance.
The structure of training zones can vary – some coaches will use a five zone method, and others will use a six or seven zone method. For the purposes of this article, we’ll be referring to the six zone method of quantifying training.
Training zone guide
Knowing what each training zone means, and what the effort should feel like gives you a quick and easy way to understand how intense a training session should be. Having a good balance of recovery, steady efforts and high intensity work in your training schedule will help you to get strong fitness gains without burning out. Keep reading to find out more about each zone, and the training benefits they bring.
Zone 1
Zone 1 is your ultra-easy, active recovery training zone. The heart rate is slightly elevated from base line, but not so much that you’re out of breath. For example, a very light jog or spinning your legs super easy on the bike.
BENEFITS OF ZONE 1 TRAINING
The purpose of working in Zone 1 is to gently stimulate blood flow. This can be beneficial at the start of a workout to begin warming up the muscles and joints to prepare them for harder efforts. Or as part of your recovery strategy to help repair sore muscles by increasing blood flow, which in turn speeds up the delivery of oxygen and repair agents and the removal of waste products. If you’re struggling with delayed onset muscle soreness (DOMs) after a tough training day, some gentle Z1 active recovery can help to ease muscle soreness and stiffness.
Zone 2
Zone 2 can be the unsung hero of endurance training. It’s not flash or impressive, and it can be kind of boring. But it brings with it a huge range of benefits that will set you up to be able to execute the big, kudos-attracting efforts to a far higher level.
Think of Zone 2 as the bread and butter in your triathlon training sandwich. Or the strong foundation, if you prefer an architectural metaphor. Zone 2 is your easy endurance pace. You’re putting in a small amount of effort, elevating the heart rate above active recovery. But you can still comfortably hold a conversation and your breathing rate, while increased from resting, isn’t significantly elevated.
When you’re working in Zone 2, you should have that “I could do this all day if I needed to” feeling. It’s really important to use objective data – ideally heart rate – when you’re trying to stick to Zone 2 to make sure you’re physiologically working the right energy zone. Most of us think we’re going easy and staying in Zone 2, when in reality we’re creeping up into Zone 3.
BENEFITS OF ZONE 2 TRAINING
For endurance athletes, Zone 2 training is going to be a key part of your training schedule. Quality time in Zone 2 helps to develop your aerobic fitness by improving cardiovascular efficiency. By working the aerobic energy system at the lower intensity, the body becomes more efficient at delivering oxygen to the muscles and utilising that oxygen to create energy. The body also gets better at clearing lactate by using it as a fuel source. This will raise your first lactate threshold, and enable you to go faster for longer before the onset of fatigue.
Zone 2 training also helps the body to improve fat oxidisation. The better your body is at using fat as a fuel, the less you’ll have to rely on carbohydrate to produce energy.
“Having a good fat oxidation will allow you to rely on fats to provide a large proportion of your energy requirements rather than using the finite glycogen stores which ideally should be conserved for periods of higher intensity or later in an event.”
Lucija Petrovic, expert physiologist at Loughborough University Performance Lab
This is useful for endurance athletes because when we burn carbohydrates, we also produce lactate. After a certain amount of time the body can no longer clear lactate quickly enough, so it begins to accumulate in the bloody. As we produce lactate, we also produce hydrogen ions which together form an acid, and create the burning fatigued sensation in the muscles which cause you to eventually slow down or stop. If you can train your body to utilise fat as its primary fuel source for longer, at higher intensities, you’ll delay the accumulation of lactate and the associated sensation of fatigue. Being able to utilise fat more effectively also reduces the overall amount of carbohydrate you have to take on during a race, which is ideal if you struggle to stomach a lot of energy gels.
WHY ZONE 2 TRAINING ISN’T A WASTE OF TIME
We can often fall into the trap of thinking that if we want to be able to race faster over longer distances, we’ve simply got to go faster in all of our training sessions. And while that might work to boost your fitness in the short term, it’s not sustainable. Over-reaching in training is a recipe for injury and burnout long term.
Training ‘easy’ in Zone 2, even if it means leaving your ego at home and embracing a bit of boredom, will stimulate the correct energy systems to facilitate being able to push harder and race faster when it counts. Which is why it should make up a significant portion of your weekly training hours. But not all of them. Of course, if you only ever train at Zone 2 – you’re just going to get really good at going at a steady pace for a long time. If getting faster is the aim, you need to complement your Zone 2 training with higher intensity work that’s going to ensure you’ve got some top end fire power when you need it.
Use data such as heart rate, pace and power to keep yourself disciplined and actually stay in Zone 2 if that’s the aim of the session. Doing so will mean that you’re not putting unnecessary fatigue into your body, so you’ve got the energy to go hard in your higher intensity sessions. Many of us do our easy sessions too hard, and our hard sessions not hard enough. Get the balance right, and you’ll soon see big fitness gains.
Zone 3
Zone 3 is often the zone we creep into when we think we’re doing Zone 2. That’s because the intensity feels manageable enough to hold for a few hours, but hard enough that we also ‘feel’ like we’re working. It ticks the box of ‘I feel like I’m working pretty hard so this must be beneficial’, whereas many people find Zone 2 feels too easy and struggle to trust that it’s helping them to build fitness. If the last few miles of your ‘easy Zone 2’ long rides and runs always feel like a drag, chances are you’re probably working in Zone 3.
Zone 3 is where we typically hit our first lactate threshold – the point where blood lactate levels rise above the base line. At this intensity, the body can clear the lactate effectively by using it as fuel which enables us to maintain the effort for a few – or even several – hours. In terms of racing, Zone 3 would be your marathon race pace or Ironman race effort.
BENEFITS OF ZONE 3 TRAINING
Doing too much of what should be Zone 2 training at Zone 3 intensity can be an issue, because it puts your body under more fatigue. At first, you’ll probably get a nice boost in fitness. But over time, this fatigue will impact your recovery. Meaning you won’t have the energy to execute your high intensity sessions properly. And you might even end up having to take unplanned time off from training if you put yourself in too much of a hole. So too much Zone 3 training can end up being a waste of time!
That’s not to say Zone 3 doesn’t have a place in your training schedule. Used appropriately it can have benefits. Zone 3 is ideal for interval sessions with longer repeats (for example, 3 x 15 minutes) or sub-tempo sessions lasting 1-2hrs (for cycling). Zone 3 work can help to raise your first lactate threshold (LT1). In simple terms, raising your LT1 means your easy endurance pace will become faster, for the same perceived effort.
Zone 4
Zone 4 is often referred to as the ‘sweet spot’. Sitting just under your threshold pace or power output, Zone 4 feels comfortably uncomfortable. You’re working hard, the blood is pumping and it feels fairly fast without going full gas or being out of control. Depending on your fitness levels, you’d probably be able to hold your Zone 4 effort for 40-60 minutes, though as you got to close to the 1hr mark it would start to get pretty tough.
BENEFITS OF ZONE 4 TRAINING
Sessions incorporating Zone 4 would usually be medium-length intervals, with reps of around 10 minutes. Working at this intensity is a good way to raise your second lactate threshold (LT2), which will mean you can ride/run faster before lactate starts to accumulate. For cyclists, LT2 is often closely associated to your Functional Threshold Power (FTP). The good thing about Zone 4 work is that it gives you that endorphin boost of a hard session, without being so tough that it takes days to recover from the effort. Ideal for triathlon training where you’re having to train several days a week and being able to recover quickly is key to consistency.
WHAT IS FTP IN CYCLING?
In cycling we use power, expressed in watts, to quantify the amount of force being pushed through the pedals. FTP stands for Functional Threshold Power. Your FTP is a measure of your cycling fitness, and represents the maximum amount of power you’d be able to push for an hour riding.
Zone 5
% threshold power
95-105%
Things start to heat up at this stage. Zone 5 is your threshold zone, meaning you’re operating at the top end of your aerobic capacity and at the top end of the zone, just above it. Efforts in Zone 5 will feel quite tough, particularly as you get towards the end of the session. But you’re still not at a max-out effort quite yet.
BENEFITS OF ZONE 5 TRAINING
Zone 5 is ideal for shorter intervals, such as 3-5 minute repeats adding up to a total of 25-30 minutes within your training session. Typically you’ll be above your second lactate threshold (LT2) working at this intensity. This will help to boost your higher end speed, but also improve your steady endurance pace. In cycling, Zone 5 efforts are also a great tool to help you get stronger at climbing up hills.
Zone 6
If Zone 6 was on a restaurant menu, it would probably come with a spice warning and glass of milk on the side. Get ready to feel the burn! This is your maximum effort that you can sustain for between 40s and 1 or 2 minutes (depending on fitness levels). Workouts with Zone 6 efforts will feel really tough, so make sure you warm up properly and schedule in an easier session the day after to give your body chance to recover and adapt.
BENEFITS OF ZONE 6 TRAINING
Zone 6 training can help to improve your VO2 max, which in turn will give you more ‘ceiling’ to raise your thresholds. Having a high VO2 max gives you greater performance capacity. Workouts with Zone 6 efforts will help to turbo charge your fitness. They’re also a useful tool for building mental toughness and tenacity – you’ll have to get used to pushing through discomfort and tackling sessions that might sound scary on paper. That experience will be valuable on race day, because you’ll have unlocked a greater ability to keep pushing when the going gets tough.
WHAT IS vo2 max? expert insight
“VO2 max is the maximum volume of oxygen that you are able to take up and use. This can be used as an indicator of endurance performance potential, although the lactate thresholds are more relevant predictors of your current performance capacity.” – Lucija Petrovic, Physiologist
Now you have a better understanding of what training zones are and how working in the different zones can benefit your fitness, head over to our Indoor Cycling and Indoor Running sections where you’ll find some of our recommendations for various workouts that will help you to do everything from boost your marathon run pace to turbo charge your cycling hill climbing skills.
