I’ve noticed lately that a lot of people on various social media groups are asking questions about their training zones and how they can be fit in each zone. It occurred to me that there is a lot of information out there about training zones but it still leaves people feeling confused, perhaps because there are lots of different systems which use different calculations, metrics and language.

So what are my training zones? Here is a summary of training zones for running:-

Chart showing training zones

Ok, so there’s a lot of terminology in there which can be confusing both because terms are often used interchangeably and because without having consciously done lots of training in these different zones they can seem a bit meaningless.

LTHR or Lactate Threshold Heart Rate is the term used to describe the effort at which the lactate inflection point occurs; in very basic terms the point at which the blood lactate concentration begins to increase faster than its rate of use.

FTPa or Functional Threshold Pace is the fastest (consistent) pace that you can maintain for 40 minutes to an hour to exhaustion (ie at the end of the run you cannot run any more at that pace).

CP or Critical Power is roughly (but not exactly) equivalent to Functional Threshold Pace (and Functional Threshold Power).

There are lots of articles and studies which describe these terms in more detail and any good sport science book will give you a detailed explanation of the physiology behind these terms.

RPE or Rate of Perceived Exertion. Some studies have shown that the majority of experienced athletes are pretty good at ‘running to feel’ ie given an understandable points scale that correlates to the different zones they will generally run in the correct zone following the system. This is good to know, especially if you really don’t want to be bothered with a complicated training computer.

Heart Rate, Pace, Rate of Perceived Exertion or Power?

As you can see there are zone guides for Heart Rate, Pace, Power and Rate of Perceived Exertion so what’s the difference?

Briefly, heart rate is measuring your beats per minute and as you work harder your heart beats faster; this is a good way of measuring the effort you are putting in. So for trail running this is perfect because your effort can change drastically depending on whether you are on a runnable tinder track or on a steep rocky ascent. Fitness can be measured by the amount of time it takes you to complete a set course at a set heart rate – this doesn’t have to be down to the last cm but could just be for example your usual 30 min Monday morning run in zone 2.

Trail running is not on even surface so pace and power can vary according to terrain

If heart rate measures what you are putting in, pace and power measures the output; pace in min/mile or min/km; power in watts. The more effort you put in the faster you will go and the more power you will produce. Pace and Power have some advantages over heart rate in that they do not change in and of themselves with extreme conditions or emotions of a race, and they respond quickly to changes in effort. Fitness can be measured by an ability to maintain a higher pace/power over a given distance or time and by a rise in Functional Threshold Pace and/or Critical Power.

Rate of Perceived Exertion is based solely on the athlete’s personal view of their effort (which has been shown to be accurate in experienced athletes). Fitness can be measured by doing a set course at a set Rate of Perceived Exertion and seeing if you can do it faster. However, the desire to do well and the excitement of a test/race can interfere with the results; in other words this system is not objective.

As you can see there are pros and cons to all and whilst my primary preference is to train and set sessions to heart rate, I also keep an eye on pace and test for both. As it’s the same test, this is no hardship to the athlete. Given the pros and cons of each metric, it can be a good idea to use a combination so that you have a good balance of all the things you need to both pace a work out and monitor your fitness levels.

So how do we work out our Lactate Threshold Heart Rate and/or Functional Threshold Pace/Critical Power (which whilst not exactly the same, can be seen to be equivalent for our purposes)?

The best way to do it is to do a test.

I find the simplest test for LTHR and FTPa is the one advocated by Joe Friel which you perform as follows:-

  • Warm up for a good 15 – 20 minutes and include in this some faster paced running (a few strides in which you accelerate for 30s then jog, making each acceleration slightly faster than the last until you are at or about the goal pace of the upcoming session are a good way to do this).
  • Run as hard as you can on a good (flattish) surface for 30 minutes, as if you were racing for the full 30 minutes. 10 minutes into the effort press the lap button on your watch.
  • Cool down for 10 minutes afterwards (even if this means just walking about a bit).

Your Functional Threshold Pace is the average pace that you sustained for the full 30 minutes.

Your Lactate Threshold Heart Rate is the average heart rate that you sustained for the last 20 minutes of the effort.

For Critical Power, there are a number of tests, you can perform such as this one:

  • Warm up for a good 15-20 minutes including some faster paced running as described above or as you choose to get your heart rate up and your legs turning.
  • On (flattish) runnable terrain run as hard as you can for 3 minutes; this is an all out effort with the aim to run to complete exhaustion by the end of the 3 minutes.
  • Take a FULL recovery (25-30 minutes walk/jog).
  • Run as hard as you can for 9 minutes; again this is an all out effort with the aim to run to complete exhaustion by the end of the 9 minutes.
  • Cool down for 10 minutes afterwards.

Your Critical Power is 90% of the mean of the average powers for both efforts (Average power for 3 minutes + Average power for 9 minutes/2 x 0.9).

Once you have these values you can calculate the other zones, although most good training interfaces will do this for you based on the calculated FTPa/CP/LATHR. General advice is to repeat the test(s) every four to six weeks, so that as you get fitter (which you will) you can update your training zones.

There are of course several ways of describing your zones. I use Joe Friel’s zones because they are backed by evidence from runners and because they do not rely on formulas (e.g. 220-age) which are not always accurate. However there are many other systems out there, some of which are taken and calculated from Functional Threshold Pace/CP and/or Lactate Threshold Heart Rate and some of which are taken from Maximum Heart Rate/Pace. I summarise three different methods for heart rate alone below. In reality they all correlate generally well with each other, as you can see:-

Andy Coggan/Hunter Allen’s system is one I have trained with in the past, but more recently have shied away from it because it is essentially based on power zones for cyclists and I prefer to use a system that has been developed for runners. That said this is simply a personal preference and as you can see their scale correlates well with Joel Friel’s and their point that heart rate becomes irrelevant for short hard efforts is true, at this point heart rate fails as a guide because it takes too long to respond and we have to resort to pace, power or rate of perceived exertion.

Sally Edwards bases her zones, which are designed for more general endurance training (she is a very successful triathlete herself) on a % of maximum heart rate. She suggests using either the formula of 220 – age to get the initial score or doing a maximum heart rate test (ramp test or 2 by 3 minutes with full recovery between the repetitions where you are likely to reach of maximum heart rate in the second 3 minute effort). Again, I have trained using this system (although I took my maximum reading from a 5km race with a sprint at the end) to good effect in the past.

So, it doesn’t really matter what system you use, so long as you use the same system consistently and you know your values for the zones and know what zones to use and when. The main thing to be aware of when training, especially when following a prescribed plan, is what exactly the writer of the plan means when they refer to various zones. As you can see there are slight differences and in particular if the writer has used words to describe a zone, then you could end up misunderstanding and training at the wrong intensity. Most good plans will be specific about the intensity they expect you to train at in each session, but if you are not sure, always contact the writer of the plan for more clarification.

For running purposes, however, the main thing to think about is what intensity you want your run to be and (illness and injury aside) this will be based on 2 things:-

1) Your overall goal(s)

2) Your goal for that particular session

By far and above the most training that you should be doing is in zones 1-2.

Stephen Seiler has put some great research together into endurance training which clearly shows that the most important aspect of any training programme to gain fitness and speed is zone 1-2 training. Yes, that’s right, the main bulk of your training (80% of your training sessions) should be at an easy conversational intensity; an effort that you can keep going for a long time (hours when trained). We gain the most running fitness when we do a lot of running and the only way we can do a lot of running is to keep it easy.

That said running easy will only take you so far, some other training stimulus will eventually be needed for you to gain more speed. In addition, there are some fitness gains to be had by doing other types of training, so a very small amount of your training (20% of your training sessions) can be at higher intensities to:

  • Train your fast twitch muscle fibres
  • Help you make some good fitness gains in a short session
  • Habituate you to the pace of your target race
  • Provide you with some fatigue resistance
  • Provide you with some strength (e.g. up hill running strength)
  • Provide you with some sprinting ability for the end of a race
  • Increase your overall pace and fitness

The advantage of these harder sessions is that you can improve with short training sessions so it can be a good way to maximise the time you have, so long as you keep to the 80/20 rule.

So once you have your training zones, with careful planning you can maximise the time you have available so that you can make good fitness gains. Careful planning is key because where you place these sessions in your weekly training cycle (or micro-cycle) affects how much you will get out of them. This is where the descriptions for Coggan and Hunter’s zones come in handy because they give clear guidance about how frequently and in what state you can do various levels of intensity. Basically if you want to train hard and benefit the most from higher intensity workouts you need to come at them rested and fresh. So it’s no good thinking that you can smash out zone 4 training 5 times a week, this will simply get you tired and over-trained and you will end up being slower or having to stop altogether.

An important aspect in this which is actually ironically very difficult for most runners to discipline themselves to do is to make sure that their zones 1-2 sessions truly are in zones 1-2; if you do these too fast you won’t gain the running efficiency that these easier sessions target and you simply won’t be rested enough for your hard sessions. If you never fully recover you will slip into ‘the pool of mediocrity’ where your easy runs are a bit too hard and you can’t do your hard runs hard enough (because you are too tired) and you gain none of the fitness goals from any of the sessions. Knowing your zones, setting them correctly on your training watch and even having it beep at you if you go too fast, is a really good way of making sure that all your sessions are at the right intensity.

Additional Questions

What if I don’t have a training computer? You can still moderate your training to good effect using Rate of Perceived Exertion as described above. You can then monitor fitness by doing a regular test run/course at a set rate of perceived exhaustion and noting the time it takes (any simple digital watch will do this, or even just your phone).

What if I use one zone system but my training plan advocates another? In this case there is no harm in recalculating your zones according the plan’s or you can contact the writer and ask for their advice about using your usual training zone system. It’s a good idea to choose a plan that focuses on your preferred metric (e.g. if you mainly train to heart rate choose a plan that sets training to heart rate). Many plan writers will be able to guide you or may even have a plan for different metrics.

Clare Pearson
Post by Clare Pearson
January 26, 2021
A professional endurance coach since 2018, Clare Pearson has worked with endurance cyclists and runners to help them achieve their goals. Clare specialises in endurance events, she loves to work with people to help them succeed at their own goals; whether that's a personal best, a completion, a podium or better emotional health. Clare will work with you to design a plan that fits in with your day to day life and helps you get the most out of each session.