You might have seen some of our athletes adding the letters ‘PE’ and a number at the end of their Strava run names. Wondering what that’s all about? Well read on!

An important part of any training plan or program is to manage the training ‘load’. Load is a measure of the total amount and intensity of training over a period – usually a week. Load matters for two key reasons:

  1. For a training plan to be progressive, we would usually look to increase the load steadily for three weeks before dropping it back (a ‘recovery/rest’ week) and then building up again. This pattern allows the particular areas of fitness being focused on to be developed.
  2. Research shows (see reference 1 below) that spikes in load – i.e. a week with significantly higher load than the preceding weeks) can increase the risk of injury very significantly.

Therefore it is important for us to be aware of our loadings and ensure we aren’t creating such ‘spikes’, whilst also ensuring our training is progressive and leading us towards our goals.

The way we measure load in these programs is to use a simple technique using a tool called the Borg Scale of Perceived Exertion (reference 2 below). The Borg Scale deliberately asks the individual to rate how hard a particular activity felt to them, rather than trying to measure the objective effort involved in completing it. The original scale is from 6 (no exertion – e.g. reading a book) to 20 (very, very hard – e.g. a finishing kick in a race). You can see the full Borg Scale here:

To make things a little bit simpler, we use a slightly simplified scale of 6 to 10 to rate each of our training sessions:

PEDescriptionBorg's definitionOur training definitions
6Fairly lightWalking slowlyVery easy / Recovery jog / 60% or less of max heart rate / Zone 1 / below lactate threshold
7Somewhat hardBrisk walk or slow jog, enough to increase your heart rate and breathing but not get out of breathEasy / Easy run / 60-80% of max heart rate / Zone 2 / around lactate threshold
8HardVigorous effort that makes your heat pound and breathing fastComfortable / Steady run / 80-90% of max heart rate / Zone 3 / between lactate threshold and lactate turn-point
9Very hardThe highest level of activity you can sustainUncomfortable / Tempo run / 90-95% of max heart rate / Zone 4 / at or above lactate turn-point
10Very, very hardA finishing kick in a race or other burst of activity that you can't maintain for longUnsustainable / Sprint / 95%+ max heart rate (at end of race; primarily anaerobic) / well above lactate turn-point

The recommendation is to make the assessment of perceived exertion around 30 minutes after the session. For most of us that roughly coincides with when we’ll post our Strava run and that’s why athletes on some of our programs can be seen to be doing that.

However, perceived exertion is only one part of load: I might sprint round a field at PE 10, but that would be far less load than running a marathon even at PE 7. To estimate load we need to take into account how long the session is too.

So our estimate of session load is simply the perceived exertion multiplied by the duration in minutes:

LOAD = PE x duration (mins)

So my sprint round a field for a couple of minutes might be PE 10 x 2 minutes = load of 20. Whereas my leisurely 4 hour marathon might be PE 7 x 240 minutes = load of 1,680.

By marking each session like this, we can then add up the sessions each week to find out our weekly loading, and then compare each week to the previous weeks to look for progression (and recovery/rest) without any ‘spikes’.

If you would like more information about this or anything else running related, please feel free to speak to our head coach, Chris Lees, or any of the other club coaches.


  1. “Spikes in acute:chronic workload ratio associated with a 5-7 times greater injuiry rate in English Premier League football players”, Bowen, Gross, Gimpel, Bruce-Low and Li, 2018 (
  2. “Medicine and Science in Sports and Exercise: Psychophysical bases of perceived exertion”, Borg, 1982 (

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