Training zones are designed to maximise physiological adaptations to your swim, bike and run efforts, and reduce the chances of injury.
In other words, by training at varying intensities, you stimulate different adaptations that are all conducive to optimum triathlon performance, whether it’s more speed, stamina or power.
How many training zones are there?
In exercise physiology many scientific studies refer to three main intensity zones: one, two and three. Imaginative! This is largely because these zones are the easiest to identify and thus study the effects of training.
What's the most important training zone?
I like to think of the three zones in triathlon terms as: Work, Specifics and Capacity. Zone one is the Work you do, long sessions at low intensity. I believe training in this zone is the most important.
It creates the building blocks for the other two zones and without plenty of Work you won’t be able to sustain your Specifics.
If you’ve got a good amount of Work in the bank, a good performance is only a few weeks away, whereas without it you might be months away. As a rule of thumb, around 70-85% of your overall training volume should be in this zone.
Also, do remember that an 80min interval running session will likely be comprised of 20-30mins of Specifics or Capacity intensity, while the other 50-60mins will be Work.
Specifics, for athletes racing non-drafting sprint, Olympic and even up to 70.3, is work done at or around race pace. It’s the training you do to hone into your event demands, or to push your Specifics (Threshold) abilities higher. Somewhere between 15-25% of weekly volume in this zone is a good place to aim.
Studies have shown that too much time spent in Specifics does not result in improved performance and increases overtraining risk.
That leaves us with Capacity, where you’re working a mix of top-end aerobic and anaerobic ability. This includes VO2 max – worth noting because it’s a maximal capacity, the limit of your body’s ability to process oxygen.
I tend to think that training in this zone is mainly about creating space for your Specifics to move into. If you have a high Capacity on the bike, for example, it’s probably not worth doing a lot of work there and more productive to focus on Work and Specifics.
Conversely, if you find that there’s not a lot of difference between your top-end Specifics and your Capacity, you’ll probably need to move your Capacity if your Specifics are to improve.
Time spent in this zone weekly should probably be no more than 5% of overall volume. All training needs to be tailored to the individual and specific to the event you’re training for, but a plan based on solid scientific data is a good place to start.
How to calculate training zones
To calculate training zones you need to first work out what your maximum heart rate is when you are working out at your maximum. In his blog top Ironman coach Joe Friel advises this method;
"To find your LTHR (lactose threshold heart rate) do a 30min time trial all by yourself (no training partners and not in a race). Again, it should be done as if it was a race for the entire 30 minutes.
"But at 10 minutes into the test click the lap button on your heart rate monitor. When done look to see what your average heart rate was for the last 20 minutes. That number is an approximation of your LTHR."
From here you can then work out the following training zones:
Zone 1
Zone one is measured as anything below Lactate Threshold 1 (Lt1), where the body is producing but utilising lactate and the level remains stable. This zone, for a well-conditioned athlete fuelling properly, is for training sessions up to 2-5 hours.
% of max heart rate (range)
SWIM 50-60%
BIKE 60-65%
RUN 50-60%
Perceived exertion (out of 10, 10 being maximal exertion): RPE 2-4, easy to moderate
Performance benefit(s): Training at this intensity will boost your recovery and prepare you to train in the higher heart rate zones.
Zone 2
Zone two starts where zone one ends and ends when the body starts to rapidly produce more lactate than it can clear. The top of this zone is called various things but often Lactate Threshold 2 (Lt2) or Threshold.
For many athletes this is for sessions between 30 and 90mins and in well-trained athletes this is the racing intensity for sprint- to Olympic-distance events.
% of max heart rate (range)
SWIM 60-70%
BIKE 65-75%
RUN 60-70%
Perceived exertion: RPE 4-5, moderate
Performance benefit(s): Basic cardiovascular training at a good recovery pace. This is the intensity to improve aerobic capacity; in other words, stamina. Your body will get better at oxidising – burning – fat and your muscular fitness will increase along with your capillary density.
Zone 3
Zone three is anything above where zone two ends and is where the body is producing way more lactate than it can use or clear.
At this point, a percentage of your energy is coming from your anaerobic system, so is only sustainable for shorter efforts and often broken into intervals in training to allow more accumulation of time, generally between 15 and 45mins of work in a given session.
% of max heart rate (range)
SWIM 70-80%
BIKE 75-82%
RUN 70-80% of max HR
Perceived exertion: RPE 5-7, moderately hard
Performance benefit(s): Running in zone 3 is especially effective for improving the efficiency of blood circulation in the heart and skeletal muscles. This is the zone in which lactic acid starts building up in your bloodstream. Training in this zone will make moderate efforts easier and improve your efficiency.
What is Zone 4 and Zone 5?
Zone 4
SWIM 80-90%
BIKE 82-89%
RUN 80-90% of max HR. When intensity is at an upper limit, to increase speed.
Perceived exertion: RPE 7-9, very difficult
Performance benefit(s): This zone will improve your anaerobic capacity, threshold and speed endurance. Your body will get better at using carbohydrates for energy and you’ll be able to withstand higher levels of lactic acid in your blood for longer.
Zone 5
SWIM: 90-100%
BIKE: 90-100%
RUN: 90-100%
Perceived exertion: RPE 9-10, maximal
Performance benefit(s): Training at maximum (i.e. interval training) will increase your anaerobic and muscular endurance, power and cardiovascular levels.
Top image credit: Jonny Gawler
