What is CTL?
CTL stands for Chronic Training Load (Strava call it fitness). It’s a training metric based off your load over a longish period of time (usually around 6 weeks). Those that have a power meter will probably have heard of this along with TSS (Training Stress Score), ATL (Acute Training Load) and TSB (Training Stress Balance). They work together to show a representation of someone’s training load.
A lot of people base their training around building their CTL. Managing load is extremely important so as not to overload or under load someone. The approach of increasing people’s CTL to develop their fitness is a valid one, however it’s only part of the the picture.
When may it not work so well?
CTL and it’s friends are a way of measuring the training stress on the body, and extrapolations can be made from that about susceptibility to injury, sickness and overtraining. However, possibly it’s biggest shortfall is that it doesn’t measure other stresses which can have just as big an effect.
The obvious ones here are other sports/gym work. These can be estimated and their stress can be included. However, without as precise a way of measuring load as power it is prone to inaccuracies, throwing out the accuracy of the whole system.
The not so obvious ones are emotional, psychological and work stress. These all will have a major effect on people's recovery, so are an inevitable limitation of the system.
Today’s Plan uses daily metrics of fatigue, muscle soreness etc, which are very helpful for the coach to know what’s happening inside the athlete’s body, but it ultimately comes down to the athlete being honest to themselves about how they feel.
The last, and one of the most important factors is sleep (not just duration but quality). Sleep has been shown to have a major effect on recovery, and all athletes should be aware of how well they are sleeping. Plenty of athletes see great improvements in fitness from improving sleep alone.
When else may it not work?
Returning from time off: If someone who has previously been fit comes back from a very low base they may be able to handle much more than someone who has never previously done serious training before. They will find they can hold a larger TSB (the difference between short term training load (ATL) and long term training load (CTL)) and hold it for longer as they come back.
You can see on my Load and Performance chart above that my TSB has got very large (into the range of -60, which is generally far too large) and has been consistently around -30 which is very tough to maintain. However, my previous training allows my body to handle this early in my comeback.
In the last few weeks I have upped my threshold from 220W up to 260W (and up from 180 when I started training). I have started doing efforts, and my threshold has felt like it has sky-rocketed so I have had to adjust. However, in doing this it has become a lot harder to increase my CTL. I kept pushing through for about a week but I got very fatigued, so decided to plateau my CTL to allow my TSB to return to a much more manageable number.
When the FTP changes it has a large effect on the ATL and CTL calculations, which makes it difficult to continue to increase CTL straight away. For this reason, I would recommend a week or 2 of plateau.
So although CTL is a great tool, it is not everything. It needs to be considered in conjunction with other factors. It certainly should not be considered someone’s ‘Fitness’ as Strava claims. That’s all for now. If you would like to get in touch in touch to discuss your training and get the most out of it send an email to firstname.lastname@example.org