How To: Understand Zone Training for Swimming

In HOWTO Write a basic training system, I said we would progress from the structure of a simple one hour or more training system to devising a more comprehensive swim training plan.

A long time ago I wrote a post on introducing interval training to swimming and another on heart rate zones, that one really only included the chart below with little further explanation.

To progress in this area, we need to talk about the different types of training. The Zone System in the chart mentioned above is one way of categorising training types.

There are four or five zones depending on your preference or how you categorise them. First below is the five zone system.

Heart rates and rest intervals increase with Zone number and set distances decrease.

Zone 1: Aerobic, sometimes called endurance or even recovery. This is where swimming can be maintained with available oxygen and only low levels of lactic acid will be produced with which the body can cope or dispose. To complicate this mess of terms, Zone 1 is further subdivided into three types, recovery, maintenance and stimulus. The different types are defined by heart rate below maximum heart rate, from 70 to 30 beats below maximum. For distance open water training, e.g. training for a first 3, 5 or 10 k swim. For simplicity it’s easier to divide aerobic into recovery (easy, 50 to 70 beats below maximum), and endurance, (30 to 50 below maximum). A majority of swimming is done in the endurance zone. Strictly however, recovery is the lowest rate of aerobic training, what an experienced swimmer would categorise as very easy, or easy, at 60% to 70% maximum heart rate. Rest intervals are short and set distances can be long.

Zone 2: Anaerobic Threshold. This is where lactic acid (lactate) accumulates more quickly than the body can dispose of it. Heart rate is higher, 20 to 30 beats below maximum.

Zone 3: High performance (or Critical Speed) Endurance. This can also be called heart-rate training. It’s usually marked by increasing effort through the set, not starting too high but increasing in speed and intensity. This is the origin of a typical descending set, where times reduce and speed increases through a set, like Paul Newsome’s Red Mist set of repeating 400s. Rest intervals are longer than anaerobic threshold, from 20 to 30 seconds with heart rates 10 to 20 beats below maximum.

Zone 4: Anaerobic. Also known as race pace training, and not to be confused with Zone 2. This is commonly known also as lactate training. For most open water swimmers, this training comprises longer distances and requires longer rests. You should realise that race pace is NOT the same as sprint. The body is learning to tolerate lactic acid, and also to delay its production.

Zone 5: Sprint. This is maximum speed training and can only be performed over very short distances with long rests to stop lactate building up otherwise it becomes Zone 4. Heart rate is maximum.

One thing that can easily be noticed is the lower the zone number, the longer will be the swim distance, and the shorter the rest interval (swim long, rest short is the maxim). Obviously sprints are short distance, and long distance must be sustainable.

Using heart rate to control exercise

Using heart rate to control exercise

An alternative to the five zone system is a four zone system. This is essentially the same and just uses easier to communicate names and is based more on RPE, which is the swimmer’s Rate of Perceived Effort. Some coaches will explicitly tell swimmers to swim a set at 75% or 85% or 90% RPE.

I’ve found when explaining this, that it is important to explain that really easy swimming is about 65% of maximum heart rate. People new to exercise often think that really easy effort is more like 10% or 20%. If you use a casual ambling walk for comparison, that will still be 60 to 65% of maximum heart rate.

Your maximum heart rate drops with age, and a rough rule of thumb, (which can be justifiably criticised) is that 220 minus your age is your maximum heart rate. There are many individual variations to this.

Recovery Zone: 60% to 70%. Lowest heart rate training. This maximises fat burn and comprises long unbroken sets with short rest intervals. This is basic endurance and heart rate training. It is  also used to recover from racing, sprinting or higher level exertion.

Aerobic Zone: 70 to 80%. This zone is where much of your endurance and cardiovascular fitness comes from. Some fat is used for energy in this zone.

Anaerobic: 80% to 90%. Long distance swimmers will do a lot of training in this zone, which build up tolerance to lactic acid. However lactate buildup will eventually overwhelm the ability to perform further. Also, all energy is coming from the body’s ATP (glycogen) system and is therefore time limited.

VO² Max (Sprint): 90% to 100%. This area is for pure speed only and in only possible for a short time. The first few seconds of sprint are partly powered by creatine produced in the body, which only lasts for effort under less than 10 seconds.

In spring 2013, Evan Morrison and I collaborated on some training tips specifically for triathletes. Amongst his many excellent points, one that Evan made and noticeable in many pool lap swimmers, was that many people just swam continuously at one speed.

A rounded swimmer, or one training for an event, should be training in all different zones and at different speeds.


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8 thoughts on “How To: Understand Zone Training for Swimming

  1. Multiple sources cite maximum heart rate in water as being 12-18 bmp below the max in air in London. Your charts appear to be for the latter. Shouldn’t you use the water adjusted max HR to calculate the zones?


  2. Remember these charts are used by the heart rate monitor companies. Target market unfit people and post heart attack. So they are designed to protect them from being sue din the US. Once went to a long talk form the Technical director of Polar heart rate monitors, charts meaningless for fit people who have been raining many years.


    • Thanks for the comment, I don’t think that’s entirely correct. In that heart rate monitor companies may use them, but they weren’t designed for them. In swimming James Doc Councilman, former US Olymoic swimming was using them in the 70s. Ernie Maglischo, one of the most influential swim authors, featured Zone Training in the original Swimming Fast book (and tge later editions). And finally, I would say most swimmers and coaches still use RPE and zone training, and structure their weekly cycle around it (aerobic, threshold etc). I’ve been training and using it my entire life, and I use zone training weekly, determining whether a day is recovery, threshold, speed etc. One of the biggest challenges I see with beginning swimmers is that they tend to swim at a constant speed, instead of varying effort.



  4. Pingback: HOW TO Articles Index | LoneSwimmer

  5. This is a really interesting subject. All my work outs are based on heart rate zones. I have over 5 000 Kilometers downloaded from my heart rate monitor taken during all my training sessions and some open water events.


    • Thanks you Roger. My apologies for the late response.

      You are the person I think we could most learn from in this area, given how complete your records and experience are. Can I ask the structure of your training and what discoveries you’ve made, and what effect moving to a full heart rate training regime had for you?


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