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Required intensity of a set

Your coach will always indicate the intensity of the main-set. The words used can be confusing so here are some guidelines. Recovery and warm up swims are usually done at a low intensity. Words such as recovery, slow or easy will describe the swim. Aerobic swims are done at a low to moderate intensity. Aerobic swims are usually varied and will include different strokes, drills and swims with shorter rest periods between repetitions. Threshold swims are done at a moderate to high intensity and will involve some form of interval swimming (100-400 meter repeats) with rest periods of less that 30 seconds. Lactate swims (anaerobic and speed work) are done at a high intensity. These are short sprints of 10/15 meters up to 50 meters at maximum effort with long rest periods. The intensity indications used should however translate into something you can measure to make it more concrete and understandable.

Let’s put some structure to it. The low, moderate and high swim intensities can be expressed as percentages of maximum heart rate. These target percentages have been proven to correspond to the energy system that the body is predominantly using to fuel the workout. The following table summarizes the heart rate reserve ranges that correspond on average to  the indicated intensity. It also shows which energy system will predominantly be used during swims of that intensity.

Required intensity Lower percentage

Upper percentage

Energy system

Low or Recovery

60% of HRR


Low to Moderate

60% of HRR 85% of HRR


Moderate to High 85% of HRR

90% of HRR

 Aerobic into lactate
High to Maximum 90% of HRR 100+%


The actual percentages differ between swimmers and can be adapted as you get more familiar with your own body. You should develop your own table in time to guide you in swimming at the correct intensity. Remember that the table give a range of HR values and you may fall at the bottom, top end or in the middle of the range.

Heart rate ranges

Lets go back one step and just review the two ways to determine the target heart rate. As explained in part 2 – target heart rate can be calculated using the Karvonen (Heart rate reserve (HRR)) or the percentage of maximal heart rate (Maximum heart rate (HR max)) methods. The Karvonen method takes the resting heart rate (fitness) of a swimmer into consideration and is considered the better method to use. The formula to calculate HRR again being (220-age-Resting HR). To get the heart rate range from this you need to further calculate: HRR*Lower percentage+Resting HR and HRR*Upper percentage+Resting HR.

Let’s take a 50 year old swimmer with a resting heart rate of 50 BPM as an example:


Heart rates per minute for intensity instructions
RPE HR zone Required intensity *Lower HR Upper HR

Predominant energy system


Low or Recovery 120 140



Low to Moderate 140 150



Moderate to High 150 160


6+ High to Maximum 160 170



Heart rates per 10 seconds for intensity instructions

HR zone

Required intensity Lower Upper

Type of set


Low – Recovery; Warm up   20



Low to Moderate 20 25



Moderate to high 25 26



High 26 28  Lactate

* The values have been rounded


As with all averaged calculations it has been shown that these heart rate methods may be inaccurate for some people. This include older and specifically very fit individuals. However, it still gives a relative indication of the intensity of the training and can be adapted for individual variances. My swimmers will tell me within the first weeks of training if the ranges I calculated for them are incorrect and I will then correct the minimum and maximum heart rate indications and calculations accordingly. You can also do a maximum heart rate test at a Biokineticist or Cardiologist to determine HR max. Just remember a cycle or treadmill test will not be accurate for a swimmer. A maximal swim test should be done.

In the next part I will explain Rate of Perceived Exertion to swim at indicated intensities.