## A simple explanation of the TRIMP Studio algorithms

Apr 6

Tuesday, April 06, 2010

The TRIMP Studio lets you analyse your training and your planned training in terms of Training Load.

Put simply, Training Load is split into 2 effects:

- over a long time period, training makes you fitter
- over a short time period, training makes you more tired

These 2 effects are "estimated" using 2 metrics:

- CTL - Chronic Training Load - is a measurement at the long term effect of training
- ATL - Acute Training Load - is a measurement at the short term effect of training

So CTL is "Fitness"
And ATL is "Tiredness"

Calculation
In RunSaturday's TRIMP Studio, both CTL and ATL are calculated on a day by day basis, each using a parameter which is the constant value of that particular Training Load.

For example, if your CTL constant is 50 and your ATL constant is 10, then this means:

- if you start a day with your CTL and ATL at 10
- and during that day you do activity with a total TRaining IMPulse value of 15
- then at the start of the following day,
-- your CTL will be 10 + (15 - 10)/50 = 10.1 - you will be 0.1 fitter
-- your ATL will be 10 + (15 - 10)/10 = 10.5 - you will be 0.5 more tired

or:

- if you start a day with your CTL and ATL at 10
- and during that day you do no activity (so TRaining IMPulse value of 0)
- then at the start of the following day,
-- your CTL will be 10 + (0 - 10)/50 = 9.8 - you will be 0.2 less fit
-- your ATL will be 10 + (0 - 10)/10 = 9 - you will be 1.0 less tired

From this you can see, that:
- your CTL changes much slower than your ATL
- which is the same thing as saying that your fitness changes much slower than your tiredness.

How do you choose the values for your CTL and ATL parameters? Well, it depends a lot on your genetics and your experience. As a rough guide, something like 50 and 10 are quite good starting places to experiment. After some time:
- if you discover that your body loses fitness quickly, then you might want to think about using a CTL value lower than 50
- if you discover your body recovers from tiredness more slowly than other people, then maybe use an ATL higher than 10.

When you look at your training plan, then in general you might want to think about things like:

- aim to build your fitness (CTL) steadily and slowly
- you don't want any TRIMP spikes which are much, much higher than your current fitness (CTL)
- you might want to occasionaly take "step back" weeks where you do less activity - trying to reduce your tiredness (ATL) while not costing you any long term fitness (CTL)
- as you approach a race, you might want to taper - this is where you reduce your training, again losing a lot of tiredness (ATL) while not losing any of that fitness (CTL)
- there are a whole load of other factors not related to CTL and ATL - e.g. things like technique and speed!

One additional number that can help is a number called Training Stress Balance - TSB. This is simply the difference between CTL and ATL:
- when TSB is negative, then it means that you are still growing your fitness - you are more tired than you are fit.
- when TSB is positive, then it should mean you are bursting with energy - your fitness is much bigger than your tiredness.

Important
Please remember that this is only a guide - listen to your body, your coach and your friends too! There is no point in having a superb CTL but a bad injury!

If you want to know more about this, then please ask on the Talk page, read a book or two, and think about getting advice from a coach.

I'm no expert at this - I think some of *you* are much more knowledgeable on this than me! Definitely ask people, including on the Talk page. Also, remember that there are many different valid approaches to training - it's not one size fits all. So please treat the TRIMP/TCL/ACL/TSB models with suspicion. It does provide a tool to help you train - but you are smarter than it - it is your servant, not your master.

One final note - for power cyclists
Some people will talk about TSB in terms of Power measurements from cycling - this is a valid but different metric to TSB calculated from TRIMP/ATL/CTL.

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