How to understand Triathlon Training Zones
How to understand Triathlon Training Zones

How to understand Triathlon Training Zones

Effective pacing is key to proper injury-free training and optimum performance on your first race so, before you start, it’s worth understanding your baseline triathlon training zones and which method is right for you at least for the run and swim. Cycling pacing tends to be more power related, which is more difficult to measure without proper sensors.


If you have a training plan already, chances are it will use specific triathlon training zones for setting effort for individual sessions, mixing high and low-intensity activity to optimise the balance between performance improvement, avoiding fatigue led injury and ensuring you are training both your cardiovascular and muscular-skeletal systems. These approaches fall into three main categories and may require additional equipment to monitor.

  • HR related
  • Pace related
  • Perceived effort related

HR related

The use of Heart rate as a measure of effort makes total sense, as it is the most obvious sign that your body is working hard, can be personalised to you, and is affected by your health and fitness. On the downside, it does require a monitor to track effectively, and as a lagging indicator which takes some time to react to the effort, it’s not suited to short and variable intervals.

HR-based pacing involves splitting the range of heart rates between resting ( your heart rate when asleep or relaxed) and your maximum heart rate ( generally calculated as a function of age) into Zones, or by working back from maximum heart rate.

The body has two distinct mechanisms for burning fuel, aerobic and anaerobic ( with or without oxygen). As the muscles work harder they require more and more oxygen, and the body compensates by breathing harder and increasing blood flow. At the extremes, however, the body s not able to provide sufficient oxygen to the muscles, so more and more of the fuel is burned without oxygen ( anaerobically), which is more inefficient.

This doesn’t happen at a specific point, but progressively, meaning more and more of the energy comes from anaerobic mechanisms as the heart rate increases and the amount of lactate increases in the blood.

The Zones used in a heart rate system approximate this progression, so, an easy zone will be predominantly aerobic and efficient training at this level helps you improve your endurance without risking muscle damage. This is long slow running or relaxed swimming.

To prepare yourself for race conditions and improve speed you need to push a bit harder though, and training in zones equivalent to 75%-90% of max heart rate which will help you perform at high speeds and tempos and, most importantly, help your body deal with increasing levels of lactic acid in the blood, which are a byproduct of anaerobic exercise. This builds strength in the muscles which will help you cope with hills and sustain higher speeds.

Different coaches and equipment manufacturers use different definitions of zones, so just make sure you know what HR or zone you should be in.

Countfit has a great article that goes into more detail on the science behind Heart rate zones, so if you want to dig a little further, click here.

Runners World has a good beginners resource if you want to find out more, here

Timing based.

HR-based systems make sense because they are tied to the performance of your body and let you adjust for your condition on a given day, but they are reactive and it takes practice to get into the right zone. They are also not helpful if you are chasing a specific time.

The alternative is pace or time-based systems, which define effort based on how fast you are going relative to a personal baseline, which may be a previous race or your VO2 max.

Pace works well for triathlon training zones as it works across all three sports. If you are running or swimming it’s fairly easy to measure your speed and adjust to a specific pace, meaning these systems are much less reactive than Heart rates, making the simple to implement. HR training is not possible for Swimming in any case, as any HR monitors for use underwater tend to store the data locally, meaning you only see your performance after the event.

There are a number of calculators and options available to set your target paces and the main ones are for running, Jack Daniels, Runners World, Greg McMillan.They all do pretty much the same thing. The McMillan one is good because it allows you to go further if you wish and buy training plans for specific events.

For swimming, there are two versions which are similar but calculated in different ways, so check what your plan uses if relevant. The first, and probably most common is the Critical Swim speed ( CSS), which is the pace that you should be able to sustain for 1500m at your current level of fitness and development. Swim Smooth has a good calculator and more information on how this works and what it means in training.

RPE – Rated or relative Perceived effort

Some plans use the RPE scale which is designed to train you to judge your pace or exertion without external measures like Heart rate or pace. The idea is sound and lets you adjust your workload and pace based on how you feel on the day, so if you feel good, perhaps you can push yourself a bit harder, but if you’re tired, maybe you should dial it back.

The problem with this system, especially with beginners is in how you assess your performance objectively. If you’re naturally hard on yourself you will have a tendency to push yourself hard, which won’t improve performance because it will risk injury.

Ultimately, the right method for you will be based on equipment, preference and which training programme works for you, and most training plans will be available in.