Apr 6

Tuesday, April 06, 2010 

TRIMP is TRaining IMPulse - the idea is to give a measure of how hard you are training.

A good background article on this is

RunSaturday currently offers 4 different ways of calculating a TRIMP measure:

  1. BASIC - A simple TRIMP using Heart Rate and duration of exercise
  2. RPE - A Rate Of Perceived TRIMP - calculated using your own guess of how hard you have worked.
  3. Bannister TRIMP - using the Bannister formula on average Heart Rate
  4. Zonal Bannister TRIMP - using the Bannister formula on individual Heart Rate zone

There's no particular rights or wrongs between these - they all have merit and interest.

However, please note that these numbers generally give numbers which shouldn't be compared directly - they're different metrics on different scales.


This method requires all exercise to have an average heart rate.

It's explained on as:

"First proposed by Bannister et al in 1975, this method is a very simple way of calculating what is termed TRaining IMPulse (TRIMP). TRIMP is defined as training volume x training intensity and is specific to endurance training as it uses heart rates or heart rate zones. Initially the researchers proposed simple methods of calculating the TRIMP of a session, such as the following:

TRIMP = training time (minutes) x average heart rate (bpm). For example, 30 minutes at 145 bpm. TRIMP = 30 x 145 = 4350.

This method, involving simple maths, makes a great deal of sense in terms of calculating a ‘dose’ of aerobic training, and I would recommend it to the average adult exerciser. For adults looking to improve basic cardiovascular fitness by means of simple training sessions, such as continuous pedalling on an indoor bike, or an aerobics class, this calculation gives them a great monitoring tool to analyse their progress and adherence to training."

2. Rate of Perceived Exertion

If you've entered "Effort" estimates for each of your activities, then runSaturday can calculate a perceived measure of TRIMP.

Again from

"Foster et al developed a method of evaluating training using a variation of the Borg Rating of Perceived Exertion (RPE) scale (see table 3 below), which is designed to measure subjective perception of effort(3).

To calculate the TRIMP, the time of the session (in minutes) is multiplied by the RPE scored. For example, for 60 minutes of weight training, rated as very hard (RPE = 7), TRIMP = 60 x 7 = 420."


3. Bannister TRIMP

This method is similar to the basic method, except that instead of using average heart rate directly, then a Bannister formula is applied to your average heart rate.

This formula produces an exponential weighting to your heart rate - so that working for an hour at 90% of your working heart rate is recognised as being 4 times as hard on you as working at 70% of your working heart rate.

Compared to the basic method, the Bannister TRIMP model, rewards you more for how hard you work, not just how long you work.


4. Zone-based Bannister TRIMP

This method takes the Bannister TRIMP method even further - it splits a session up according to how long you spent in each of your heart rate zones and then calculates sub-totals for each of those zones.

The advantage of this is that it rewards effort invested in things like Interval sessions

- e.g. a session which is done half at 50% and half at 90% will receive a significantly higher TRIMP using this Zone based method, than the Bannister TRIMP method.

For some more background on this Zone-based Bannister TRIMP method


So which TRIMP should I use?

The simple answer is to have a look at all of them - all of them have merit and all of them are worth looking at:

  • BASIC emphasizes your time invested, so it is good for a measurement of how many hours you have been putting in.
  • RPE emphasizes how hard you feel you have worked - this is an interesting comparison to the "firmer" data of heart rate metrics
  • Bannister TRIMP and Zone-based Bannister TRIMP achieve a good balance between time and effort invested - with the zone-based approach providing more recognition for effort where you have detailed heart rate traces available.


How does RunSaturday TRIMP compare to TRIMP calculated in TrainingLoad within SportTracks

TrainingLoad is an excellent plugin on an excellent tool - I highly recommend both SportTracks and TrainingLoad.

I believe the algorithm used within TrainingLoad is similar to Zone-based Bannister TRIMP. So if you have similar settings for your heart rate zones within runSaturday and within SportTracks, then you should see similar TRIMP numbers too.
However, the numbers may not be exactly the same - the reason for this is because of small differences for the zone-weighting values used.
For clarification, there is some debate about which weighting score to use for a heart rate zone - if you have a heart rate zone 70-80%:

As a result, I'm afraid you can't quite compare the numbers directly.


Where can I see all this in action?

See for a discussion of the current display.

I'll try to provide further information on how to use these charts and tools in another post in a day or two.


How can I use these numbers?

Importantly these numbers can be calculated from both your training and your training plan.

This allows you to plan your training - and your tapering.

For more information, I'm hoping that some of the site's expert users will give their opinions and advice.



And what about Power?

Power meters are becoming more and more popular amongst cyclists - especially as their price drops.

Analysis of power gives a different view on how much work you have done in training - and leads to a separate set of Training Stress Scores (TSS).

RunSaturday doesn't yet support this type of power analysis.... If you're interested in helping runsaturday extend its analysis, then please get in touch :)


6 comment(s) so far...

Re: TRIMP in RunSaturday

Great explanation!! and also great to have such a tool on your site.


By dirk on   Wednesday, April 07, 2010

Re: TRIMP in RunSaturday

Thanks for the explanation! I have a couple questions:

1) If we have our HR zones set to something other than the 50%, 60%, etc. of our MHR, would that rule out using the Bannister HR Zone TRIMP?
2) Do TRIMP scores vary by sex?


By jules_SD on   Thursday, April 29, 2010

Re: TRIMP in RunSaturday

Hi Jules_SD - sorry I missed this question!

1. The site uses the half way point of each zone - so if you set a zone 73-79% then the site will use 76% for that zone.

2. No they don't - they're gender independent. I'd be interested to know if there is a difference between male/female heart rate percentages.

Hope that helps


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Re: TRIMP in RunSaturday

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Re: TRIMP in RunSaturday

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Re: TRIMP in RunSaturday

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